chiark / gitweb /
tree-wide: remove Lennart's copyright lines
[elogind.git] / src / libelogind / sd-event / sd-event.c
index 2b8d1b87ed3925c9c3462eb57b097cee798f835a..eb5d3effe5c972b67d61d625810cf4ca2a2e54bd 100644 (file)
@@ -1,41 +1,30 @@
-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
+/* SPDX-License-Identifier: LGPL-2.1+ */
 /***
-  This file is part of systemd.
-
-  Copyright 2013 Lennart Poettering
-
-  systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU Lesser General Public License as published by
-  the Free Software Foundation; either version 2.1 of the License, or
-  (at your option) any later version.
-
-  systemd is distributed in the hope that it will be useful, but
-  WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  Lesser General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public License
-  along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
 #include <sys/epoll.h>
 #include <sys/timerfd.h>
 #include <sys/wait.h>
 
-#include "sd-id128.h"
 #include "sd-daemon.h"
-#include "macro.h"
-#include "prioq.h"
+#include "sd-event.h"
+#include "sd-id128.h"
+
+#include "alloc-util.h"
+#include "fd-util.h"
+//#include "fs-util.h"
 #include "hashmap.h"
-#include "util.h"
-#include "time-util.h"
+#include "list.h"
+#include "macro.h"
 #include "missing.h"
+#include "prioq.h"
+#include "process-util.h"
 #include "set.h"
-#include "list.h"
 #include "signal-util.h"
-
-#include "sd-event.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "time-util.h"
+#include "util.h"
 
 #define DEFAULT_ACCURACY_USEC (250 * USEC_PER_MSEC)
 
@@ -52,13 +41,48 @@ typedef enum EventSourceType {
         SOURCE_POST,
         SOURCE_EXIT,
         SOURCE_WATCHDOG,
+        SOURCE_INOTIFY,
         _SOURCE_EVENT_SOURCE_TYPE_MAX,
         _SOURCE_EVENT_SOURCE_TYPE_INVALID = -1
 } EventSourceType;
 
+static const char* const event_source_type_table[_SOURCE_EVENT_SOURCE_TYPE_MAX] = {
+        [SOURCE_IO] = "io",
+        [SOURCE_TIME_REALTIME] = "realtime",
+        [SOURCE_TIME_BOOTTIME] = "bootime",
+        [SOURCE_TIME_MONOTONIC] = "monotonic",
+        [SOURCE_TIME_REALTIME_ALARM] = "realtime-alarm",
+        [SOURCE_TIME_BOOTTIME_ALARM] = "boottime-alarm",
+        [SOURCE_SIGNAL] = "signal",
+        [SOURCE_CHILD] = "child",
+        [SOURCE_DEFER] = "defer",
+        [SOURCE_POST] = "post",
+        [SOURCE_EXIT] = "exit",
+        [SOURCE_WATCHDOG] = "watchdog",
+        [SOURCE_INOTIFY] = "inotify",
+};
+
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(event_source_type, int);
+
+/* All objects we use in epoll events start with this value, so that
+ * we know how to dispatch it */
+typedef enum WakeupType {
+        WAKEUP_NONE,
+        WAKEUP_EVENT_SOURCE,
+        WAKEUP_CLOCK_DATA,
+        WAKEUP_SIGNAL_DATA,
+        WAKEUP_INOTIFY_DATA,
+        _WAKEUP_TYPE_MAX,
+        _WAKEUP_TYPE_INVALID = -1,
+} WakeupType;
+
 #define EVENT_SOURCE_IS_TIME(t) IN_SET((t), SOURCE_TIME_REALTIME, SOURCE_TIME_BOOTTIME, SOURCE_TIME_MONOTONIC, SOURCE_TIME_REALTIME_ALARM, SOURCE_TIME_BOOTTIME_ALARM)
 
+struct inode_data;
+
 struct sd_event_source {
+        WakeupType wakeup;
+
         unsigned n_ref;
 
         sd_event *event;
@@ -76,8 +100,10 @@ struct sd_event_source {
         int64_t priority;
         unsigned pending_index;
         unsigned prepare_index;
-        unsigned pending_iteration;
-        unsigned prepare_iteration;
+        uint64_t pending_iteration;
+        uint64_t prepare_iteration;
+
+        sd_event_destroy_t destroy_callback;
 
         LIST_FIELDS(sd_event_source, sources);
 
@@ -88,6 +114,7 @@ struct sd_event_source {
                         uint32_t events;
                         uint32_t revents;
                         bool registered:1;
+                        bool owned:1;
                 } io;
                 struct {
                         sd_event_time_handler_t callback;
@@ -116,10 +143,17 @@ struct sd_event_source {
                         sd_event_handler_t callback;
                         unsigned prioq_index;
                 } exit;
+                struct {
+                        sd_event_inotify_handler_t callback;
+                        uint32_t mask;
+                        struct inode_data *inode_data;
+                        LIST_FIELDS(sd_event_source, by_inode_data);
+                } inotify;
         };
 };
 
 struct clock_data {
+        WakeupType wakeup;
         int fd;
 
         /* For all clocks we maintain two priority queues each, one
@@ -136,11 +170,81 @@ struct clock_data {
         bool needs_rearm:1;
 };
 
+struct signal_data {
+        WakeupType wakeup;
+
+        /* For each priority we maintain one signal fd, so that we
+         * only have to dequeue a single event per priority at a
+         * time. */
+
+        int fd;
+        int64_t priority;
+        sigset_t sigset;
+        sd_event_source *current;
+};
+
+/* A structure listing all event sources currently watching a specific inode */
+struct inode_data {
+        /* The identifier for the inode, the combination of the .st_dev + .st_ino fields of the file */
+        ino_t ino;
+        dev_t dev;
+
+        /* An fd of the inode to watch. The fd is kept open until the next iteration of the loop, so that we can
+         * rearrange the priority still until then, as we need the original inode to change the priority as we need to
+         * add a watch descriptor to the right inotify for the priority which we can only do if we have a handle to the
+         * original inode. We keep a list of all inode_data objects with an open fd in the to_close list (see below) of
+         * the sd-event object, so that it is efficient to close everything, before entering the next event loop
+         * iteration. */
+        int fd;
+
+        /* The inotify "watch descriptor" */
+        int wd;
+
+        /* The combination of the mask of all inotify watches on this inode we manage. This is also the mask that has
+         * most recently been set on the watch descriptor. */
+        uint32_t combined_mask;
+
+        /* All event sources subscribed to this inode */
+        LIST_HEAD(sd_event_source, event_sources);
+
+        /* The inotify object we watch this inode with */
+        struct inotify_data *inotify_data;
+
+        /* A linked list of all inode data objects with fds to close (see above) */
+        LIST_FIELDS(struct inode_data, to_close);
+};
+
+/* A structure encapsulating an inotify fd */
+struct inotify_data {
+        WakeupType wakeup;
+
+        /* For each priority we maintain one inotify fd, so that we only have to dequeue a single event per priority at
+         * a time */
+
+        int fd;
+        int64_t priority;
+
+        Hashmap *inodes; /* The inode_data structures keyed by dev+ino */
+        Hashmap *wd;     /* The inode_data structures keyed by the watch descriptor for each */
+
+        /* The buffer we read inotify events into */
+        union inotify_event_buffer buffer;
+        size_t buffer_filled; /* fill level of the buffer */
+
+        /* How many event sources are currently marked pending for this inotify. We won't read new events off the
+         * inotify fd as long as there are still pending events on the inotify (because we have no strategy of queuing
+         * the events locally if they can't be coalesced). */
+        unsigned n_pending;
+
+        /* A linked list of all inotify objects with data already read, that still need processing. We keep this list
+         * to make it efficient to figure out what inotify objects to process data on next. */
+        LIST_FIELDS(struct inotify_data, buffered);
+};
+
 struct sd_event {
         unsigned n_ref;
 
         int epoll_fd;
-        int signal_fd;
         int watchdog_fd;
 
         Prioq *pending;
@@ -157,8 +261,8 @@ struct sd_event {
 
         usec_t perturb;
 
-        sigset_t sigset;
-        sd_event_source **signal_sources;
+        sd_event_source **signal_sources; /* indexed by signal number */
+        Hashmap *signal_data; /* indexed by priority */
 
         Hashmap *child_sources;
         unsigned n_enabled_child_sources;
@@ -167,16 +271,24 @@ struct sd_event {
 
         Prioq *exit;
 
+        Hashmap *inotify_data; /* indexed by priority */
+
+        /* A list of inode structures that still have an fd open, that we need to close before the next loop iteration */
+        LIST_HEAD(struct inode_data, inode_data_to_close);
+
+        /* A list of inotify objects that already have events buffered which aren't processed yet */
+        LIST_HEAD(struct inotify_data, inotify_data_buffered);
+
         pid_t original_pid;
 
-        unsigned iteration;
-        dual_timestamp timestamp;
-        usec_t timestamp_boottime;
+        uint64_t iteration;
+        triple_timestamp timestamp;
         int state;
 
         bool exit_requested:1;
         bool need_process_child:1;
         bool watchdog:1;
+        bool profile_delays:1;
 
         int exit_code;
 
@@ -188,9 +300,19 @@ struct sd_event {
         unsigned n_sources;
 
         LIST_HEAD(sd_event_source, sources);
+
+        usec_t last_run, last_log;
+        unsigned delays[sizeof(usec_t) * 8];
 };
 
+static thread_local sd_event *default_event = NULL;
+
 static void source_disconnect(sd_event_source *s);
+static void event_gc_inode_data(sd_event *e, struct inode_data *d);
+
+static sd_event *event_resolve(sd_event *e) {
+        return e == SD_EVENT_DEFAULT ? default_event : e;
+}
 
 static int pending_prioq_compare(const void *a, const void *b) {
         const sd_event_source *x = a, *y = b;
@@ -216,12 +338,6 @@ static int pending_prioq_compare(const void *a, const void *b) {
         if (x->pending_iteration > y->pending_iteration)
                 return 1;
 
-        /* Stability for the rest */
-        if (x < y)
-                return -1;
-        if (x > y)
-                return 1;
-
         return 0;
 }
 
@@ -231,6 +347,12 @@ static int prepare_prioq_compare(const void *a, const void *b) {
         assert(x->prepare);
         assert(y->prepare);
 
+        /* Enabled ones first */
+        if (x->enabled != SD_EVENT_OFF && y->enabled == SD_EVENT_OFF)
+                return -1;
+        if (x->enabled == SD_EVENT_OFF && y->enabled != SD_EVENT_OFF)
+                return 1;
+
         /* Move most recently prepared ones last, so that we can stop
          * preparing as soon as we hit one that has already been
          * prepared in the current iteration */
@@ -239,24 +361,12 @@ static int prepare_prioq_compare(const void *a, const void *b) {
         if (x->prepare_iteration > y->prepare_iteration)
                 return 1;
 
-        /* Enabled ones first */
-        if (x->enabled != SD_EVENT_OFF && y->enabled == SD_EVENT_OFF)
-                return -1;
-        if (x->enabled == SD_EVENT_OFF && y->enabled != SD_EVENT_OFF)
-                return 1;
-
         /* Lower priority values first */
         if (x->priority < y->priority)
                 return -1;
         if (x->priority > y->priority)
                 return 1;
 
-        /* Stability for the rest */
-        if (x < y)
-                return -1;
-        if (x > y)
-                return 1;
-
         return 0;
 }
 
@@ -284,15 +394,13 @@ static int earliest_time_prioq_compare(const void *a, const void *b) {
         if (x->time.next > y->time.next)
                 return 1;
 
-        /* Stability for the rest */
-        if (x < y)
-                return -1;
-        if (x > y)
-                return 1;
-
         return 0;
 }
 
+static usec_t time_event_source_latest(const sd_event_source *s) {
+        return usec_add(s->time.next, s->time.accuracy);
+}
+
 static int latest_time_prioq_compare(const void *a, const void *b) {
         const sd_event_source *x = a, *y = b;
 
@@ -312,15 +420,9 @@ static int latest_time_prioq_compare(const void *a, const void *b) {
                 return 1;
 
         /* Order by time */
-        if (x->time.next + x->time.accuracy < y->time.next + y->time.accuracy)
-                return -1;
-        if (x->time.next + x->time.accuracy > y->time.next + y->time.accuracy)
-                return 1;
-
-        /* Stability for the rest */
-        if (x < y)
+        if (time_event_source_latest(x) < time_event_source_latest(y))
                 return -1;
-        if (x > y)
+        if (time_event_source_latest(x) > time_event_source_latest(y))
                 return 1;
 
         return 0;
@@ -344,17 +446,12 @@ static int exit_prioq_compare(const void *a, const void *b) {
         if (x->priority > y->priority)
                 return 1;
 
-        /* Stability for the rest */
-        if (x < y)
-                return -1;
-        if (x > y)
-                return 1;
-
         return 0;
 }
 
 static void free_clock_data(struct clock_data *d) {
         assert(d);
+        assert(d->wakeup == WAKEUP_CLOCK_DATA);
 
         safe_close(d->fd);
         prioq_free(d->earliest);
@@ -378,7 +475,6 @@ static void event_free(sd_event *e) {
                 *(e->default_event_ptr) = NULL;
 
         safe_close(e->epoll_fd);
-        safe_close(e->signal_fd);
         safe_close(e->watchdog_fd);
 
         free_clock_data(&e->realtime);
@@ -392,6 +488,9 @@ static void event_free(sd_event *e) {
         prioq_free(e->exit);
 
         free(e->signal_sources);
+        hashmap_free(e->signal_data);
+
+        hashmap_free(e->inotify_data);
 
         hashmap_free(e->child_sources);
         set_free(e->post_sources);
@@ -404,23 +503,36 @@ _public_ int sd_event_new(sd_event** ret) {
 
         assert_return(ret, -EINVAL);
 
-        e = new0(sd_event, 1);
+        e = new(sd_event, 1);
         if (!e)
                 return -ENOMEM;
 
-        e->n_ref = 1;
-        e->signal_fd = e->watchdog_fd = e->epoll_fd = e->realtime.fd = e->boottime.fd = e->monotonic.fd = e->realtime_alarm.fd = e->boottime_alarm.fd = -1;
-        e->realtime.next = e->boottime.next = e->monotonic.next = e->realtime_alarm.next = e->boottime_alarm.next = USEC_INFINITY;
-        e->original_pid = getpid();
-        e->perturb = USEC_INFINITY;
-
-        assert_se(sigemptyset(&e->sigset) == 0);
+        *e = (sd_event) {
+                .n_ref = 1,
+                .epoll_fd = -1,
+                .watchdog_fd = -1,
+                .realtime.wakeup = WAKEUP_CLOCK_DATA,
+                .realtime.fd = -1,
+                .realtime.next = USEC_INFINITY,
+                .boottime.wakeup = WAKEUP_CLOCK_DATA,
+                .boottime.fd = -1,
+                .boottime.next = USEC_INFINITY,
+                .monotonic.wakeup = WAKEUP_CLOCK_DATA,
+                .monotonic.fd = -1,
+                .monotonic.next = USEC_INFINITY,
+                .realtime_alarm.wakeup = WAKEUP_CLOCK_DATA,
+                .realtime_alarm.fd = -1,
+                .realtime_alarm.next = USEC_INFINITY,
+                .boottime_alarm.wakeup = WAKEUP_CLOCK_DATA,
+                .boottime_alarm.fd = -1,
+                .boottime_alarm.next = USEC_INFINITY,
+                .perturb = USEC_INFINITY,
+                .original_pid = getpid_cached(),
+        };
 
-        e->pending = prioq_new(pending_prioq_compare);
-        if (!e->pending) {
-                r = -ENOMEM;
+        r = prioq_ensure_allocated(&e->pending, pending_prioq_compare);
+        if (r < 0)
                 goto fail;
-        }
 
         e->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
         if (e->epoll_fd < 0) {
@@ -428,6 +540,13 @@ _public_ int sd_event_new(sd_event** ret) {
                 goto fail;
         }
 
+        e->epoll_fd = fd_move_above_stdio(e->epoll_fd);
+
+        if (secure_getenv("SD_EVENT_PROFILE_DELAYS")) {
+                log_debug("Event loop profiling enabled. Logarithmic histogram of event loop iterations in the range 2^0 ... 2^63 us will be logged every 5s.");
+                e->profile_delays = true;
+        }
+
         *ret = e;
         return 0;
 
@@ -437,7 +556,9 @@ fail:
 }
 
 _public_ sd_event* sd_event_ref(sd_event *e) {
-        assert_return(e, NULL);
+
+        if (!e)
+                return NULL;
 
         assert(e->n_ref >= 1);
         e->n_ref++;
@@ -465,27 +586,27 @@ static bool event_pid_changed(sd_event *e) {
         /* We don't support people creating an event loop and keeping
          * it around over a fork(). Let's complain. */
 
-        return e->original_pid != getpid();
+        return e->original_pid != getpid_cached();
 }
 
-static int source_io_unregister(sd_event_source *s) {
+static void source_io_unregister(sd_event_source *s) {
         int r;
 
         assert(s);
         assert(s->type == SOURCE_IO);
 
         if (event_pid_changed(s->event))
-                return 0;
+                return;
 
         if (!s->io.registered)
-                return 0;
+                return;
 
         r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_DEL, s->io.fd, NULL);
         if (r < 0)
-                return -errno;
+                log_debug_errno(errno, "Failed to remove source %s (type %s) from epoll: %m",
+                                strna(s->description), event_source_type_to_string(s->type));
 
         s->io.registered = false;
-        return 0;
 }
 
 static int source_io_register(
@@ -493,24 +614,22 @@ static int source_io_register(
                 int enabled,
                 uint32_t events) {
 
-        struct epoll_event ev = {};
+        struct epoll_event ev;
         int r;
 
         assert(s);
         assert(s->type == SOURCE_IO);
         assert(enabled != SD_EVENT_OFF);
 
-        ev.events = events;
-        ev.data.ptr = s;
-
-        if (enabled == SD_EVENT_ONESHOT)
-                ev.events |= EPOLLONESHOT;
+        ev = (struct epoll_event) {
+                .events = events | (enabled == SD_EVENT_ONESHOT ? EPOLLONESHOT : 0),
+                .data.ptr = s,
+        };
 
         if (s->io.registered)
                 r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_MOD, s->io.fd, &ev);
         else
                 r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_ADD, s->io.fd, &ev);
-
         if (r < 0)
                 return -errno;
 
@@ -592,45 +711,176 @@ static struct clock_data* event_get_clock_data(sd_event *e, EventSourceType t) {
         }
 }
 
-static bool need_signal(sd_event *e, int signal) {
-        return (e->signal_sources && e->signal_sources[signal] &&
-                e->signal_sources[signal]->enabled != SD_EVENT_OFF)
-                ||
-               (signal == SIGCHLD &&
-                e->n_enabled_child_sources > 0);
-}
+static int event_make_signal_data(
+                sd_event *e,
+                int sig,
+                struct signal_data **ret) {
 
-static int event_update_signal_fd(sd_event *e) {
-        struct epoll_event ev = {};
-        bool add_to_epoll;
+        struct epoll_event ev;
+        struct signal_data *d;
+        bool added = false;
+        sigset_t ss_copy;
+        int64_t priority;
         int r;
 
         assert(e);
 
         if (event_pid_changed(e))
-                return 0;
+                return -ECHILD;
 
-        add_to_epoll = e->signal_fd < 0;
+        if (e->signal_sources && e->signal_sources[sig])
+                priority = e->signal_sources[sig]->priority;
+        else
+                priority = SD_EVENT_PRIORITY_NORMAL;
 
-        r = signalfd(e->signal_fd, &e->sigset, SFD_NONBLOCK|SFD_CLOEXEC);
-        if (r < 0)
-                return -errno;
+        d = hashmap_get(e->signal_data, &priority);
+        if (d) {
+                if (sigismember(&d->sigset, sig) > 0) {
+                        if (ret)
+                                *ret = d;
+                        return 0;
+                }
+        } else {
+                r = hashmap_ensure_allocated(&e->signal_data, &uint64_hash_ops);
+                if (r < 0)
+                        return r;
 
-        e->signal_fd = r;
+                d = new(struct signal_data, 1);
+                if (!d)
+                        return -ENOMEM;
 
-        if (!add_to_epoll)
-                return 0;
+                *d = (struct signal_data) {
+                        .wakeup = WAKEUP_SIGNAL_DATA,
+                        .fd = -1,
+                        .priority = priority,
+                };
 
-        ev.events = EPOLLIN;
-        ev.data.ptr = INT_TO_PTR(SOURCE_SIGNAL);
+                r = hashmap_put(e->signal_data, &d->priority, d);
+                if (r < 0) {
+                        free(d);
+                        return r;
+                }
+
+                added = true;
+        }
+
+        ss_copy = d->sigset;
+        assert_se(sigaddset(&ss_copy, sig) >= 0);
 
-        r = epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, e->signal_fd, &ev);
+        r = signalfd(d->fd, &ss_copy, SFD_NONBLOCK|SFD_CLOEXEC);
         if (r < 0) {
-                e->signal_fd = safe_close(e->signal_fd);
-                return -errno;
+                r = -errno;
+                goto fail;
+        }
+
+        d->sigset = ss_copy;
+
+        if (d->fd >= 0) {
+                if (ret)
+                        *ret = d;
+                return 0;
+        }
+
+        d->fd = fd_move_above_stdio(r);
+
+        ev = (struct epoll_event) {
+                .events = EPOLLIN,
+                .data.ptr = d,
+        };
+
+        r = epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, d->fd, &ev);
+        if (r < 0)  {
+                r = -errno;
+                goto fail;
         }
 
+        if (ret)
+                *ret = d;
+
         return 0;
+
+fail:
+        if (added) {
+                d->fd = safe_close(d->fd);
+                hashmap_remove(e->signal_data, &d->priority);
+                free(d);
+        }
+
+        return r;
+}
+
+static void event_unmask_signal_data(sd_event *e, struct signal_data *d, int sig) {
+        assert(e);
+        assert(d);
+
+        /* Turns off the specified signal in the signal data
+         * object. If the signal mask of the object becomes empty that
+         * way removes it. */
+
+        if (sigismember(&d->sigset, sig) == 0)
+                return;
+
+        assert_se(sigdelset(&d->sigset, sig) >= 0);
+
+        if (sigisemptyset(&d->sigset)) {
+
+                /* If all the mask is all-zero we can get rid of the structure */
+                hashmap_remove(e->signal_data, &d->priority);
+                safe_close(d->fd);
+                free(d);
+                return;
+        }
+
+        assert(d->fd >= 0);
+
+        if (signalfd(d->fd, &d->sigset, SFD_NONBLOCK|SFD_CLOEXEC) < 0)
+                log_debug_errno(errno, "Failed to unset signal bit, ignoring: %m");
+}
+
+static void event_gc_signal_data(sd_event *e, const int64_t *priority, int sig) {
+        struct signal_data *d;
+        static const int64_t zero_priority = 0;
+
+        assert(e);
+
+        /* Rechecks if the specified signal is still something we are
+         * interested in. If not, we'll unmask it, and possibly drop
+         * the signalfd for it. */
+
+        if (sig == SIGCHLD &&
+            e->n_enabled_child_sources > 0)
+                return;
+
+        if (e->signal_sources &&
+            e->signal_sources[sig] &&
+            e->signal_sources[sig]->enabled != SD_EVENT_OFF)
+                return;
+
+        /*
+         * The specified signal might be enabled in three different queues:
+         *
+         * 1) the one that belongs to the priority passed (if it is non-NULL)
+         * 2) the one that belongs to the priority of the event source of the signal (if there is one)
+         * 3) the 0 priority (to cover the SIGCHLD case)
+         *
+         * Hence, let's remove it from all three here.
+         */
+
+        if (priority) {
+                d = hashmap_get(e->signal_data, priority);
+                if (d)
+                        event_unmask_signal_data(e, d, sig);
+        }
+
+        if (e->signal_sources && e->signal_sources[sig]) {
+                d = hashmap_get(e->signal_data, &e->signal_sources[sig]->priority);
+                if (d)
+                        event_unmask_signal_data(e, d, sig);
+        }
+
+        d = hashmap_get(e->signal_data, &zero_priority);
+        if (d)
+                event_unmask_signal_data(e, d, sig);
 }
 
 static void source_disconnect(sd_event_source *s) {
@@ -669,17 +919,11 @@ static void source_disconnect(sd_event_source *s) {
 
         case SOURCE_SIGNAL:
                 if (s->signal.sig > 0) {
+
                         if (s->event->signal_sources)
                                 s->event->signal_sources[s->signal.sig] = NULL;
 
-                        /* If the signal was on and now it is off... */
-                        if (s->enabled != SD_EVENT_OFF && !need_signal(s->event, s->signal.sig)) {
-                                assert_se(sigdelset(&s->event->sigset, s->signal.sig) == 0);
-
-                                (void) event_update_signal_fd(s->event);
-                                /* If disabling failed, we might get a spurious event,
-                                 * but otherwise nothing bad should happen. */
-                        }
+                        event_gc_signal_data(s->event, &s->priority, s->signal.sig);
                 }
 
                 break;
@@ -689,18 +933,10 @@ static void source_disconnect(sd_event_source *s) {
                         if (s->enabled != SD_EVENT_OFF) {
                                 assert(s->event->n_enabled_child_sources > 0);
                                 s->event->n_enabled_child_sources--;
-
-                                /* We know the signal was on, if it is off now... */
-                                if (!need_signal(s->event, SIGCHLD)) {
-                                        assert_se(sigdelset(&s->event->sigset, SIGCHLD) == 0);
-
-                                        (void) event_update_signal_fd(s->event);
-                                        /* If disabling failed, we might get a spurious event,
-                                         * but otherwise nothing bad should happen. */
-                                }
                         }
 
-                        hashmap_remove(s->event->child_sources, INT_TO_PTR(s->child.pid));
+                        (void) hashmap_remove(s->event->child_sources, PID_TO_PTR(s->child.pid));
+                        event_gc_signal_data(s->event, &s->priority, SIGCHLD);
                 }
 
                 break;
@@ -717,6 +953,41 @@ static void source_disconnect(sd_event_source *s) {
                 prioq_remove(s->event->exit, s, &s->exit.prioq_index);
                 break;
 
+        case SOURCE_INOTIFY: {
+                struct inode_data *inode_data;
+
+                inode_data = s->inotify.inode_data;
+                if (inode_data) {
+                        struct inotify_data *inotify_data;
+                        assert_se(inotify_data = inode_data->inotify_data);
+
+                        /* Detach this event source from the inode object */
+                        LIST_REMOVE(inotify.by_inode_data, inode_data->event_sources, s);
+                        s->inotify.inode_data = NULL;
+
+                        if (s->pending) {
+                                assert(inotify_data->n_pending > 0);
+                                inotify_data->n_pending--;
+                        }
+
+                        /* Note that we don't reduce the inotify mask for the watch descriptor here if the inode is
+                         * continued to being watched. That's because inotify doesn't really have an API for that: we
+                         * can only change watch masks with access to the original inode either by fd or by path. But
+                         * paths aren't stable, and keeping an O_PATH fd open all the time would mean wasting an fd
+                         * continously and keeping the mount busy which we can't really do. We could reconstruct the
+                         * original inode from /proc/self/fdinfo/$INOTIFY_FD (as all watch descriptors are listed
+                         * there), but given the need for open_by_handle_at() which is privileged and not universally
+                         * available this would be quite an incomplete solution. Hence we go the other way, leave the
+                         * mask set, even if it is not minimized now, and ignore all events we aren't interested in
+                         * anymore after reception. Yes, this sucks, but â€¦ Linux â€¦ */
+
+                        /* Maybe release the inode data (and its inotify) */
+                        event_gc_inode_data(s->event, inode_data);
+                }
+
+                break;
+        }
+
         default:
                 assert_not_reached("Wut? I shouldn't exist.");
         }
@@ -742,6 +1013,13 @@ static void source_free(sd_event_source *s) {
         assert(s);
 
         source_disconnect(s);
+
+        if (s->type == SOURCE_IO && s->io.owned)
+                s->io.fd = safe_close(s->io.fd);
+
+        if (s->destroy_callback)
+                s->destroy_callback(s->userdata);
+
         free(s->description);
         free(s);
 }
@@ -779,6 +1057,27 @@ static int source_set_pending(sd_event_source *s, bool b) {
                 d->needs_rearm = true;
         }
 
+        if (s->type == SOURCE_SIGNAL && !b) {
+                struct signal_data *d;
+
+                d = hashmap_get(s->event->signal_data, &s->priority);
+                if (d && d->current == s)
+                        d->current = NULL;
+        }
+
+        if (s->type == SOURCE_INOTIFY) {
+
+                assert(s->inotify.inode_data);
+                assert(s->inotify.inode_data->inotify_data);
+
+                if (b)
+                        s->inotify.inode_data->inotify_data->n_pending ++;
+                else {
+                        assert(s->inotify.inode_data->inotify_data->n_pending > 0);
+                        s->inotify.inode_data->inotify_data->n_pending --;
+                }
+        }
+
         return 0;
 }
 
@@ -787,21 +1086,24 @@ static sd_event_source *source_new(sd_event *e, bool floating, EventSourceType t
 
         assert(e);
 
-        s = new0(sd_event_source, 1);
+        s = new(sd_event_source, 1);
         if (!s)
                 return NULL;
 
-        s->n_ref = 1;
-        s->event = e;
-        s->floating = floating;
-        s->type = type;
-        s->pending_index = s->prepare_index = PRIOQ_IDX_NULL;
+        *s = (struct sd_event_source) {
+                .n_ref = 1,
+                .event = e,
+                .floating = floating,
+                .type = type,
+                .pending_index = PRIOQ_IDX_NULL,
+                .prepare_index = PRIOQ_IDX_NULL,
+        };
 
         if (!floating)
                 sd_event_ref(e);
 
         LIST_PREPEND(sources, e->sources, s);
-        e->n_sources ++;
+        e->n_sources++;
 
         return s;
 }
@@ -818,7 +1120,8 @@ _public_ int sd_event_add_io(
         int r;
 
         assert_return(e, -EINVAL);
-        assert_return(fd >= 0, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
+        assert_return(fd >= 0, -EBADF);
         assert_return(!(events & ~(EPOLLIN|EPOLLOUT|EPOLLRDHUP|EPOLLPRI|EPOLLERR|EPOLLHUP|EPOLLET)), -EINVAL);
         assert_return(callback, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
@@ -828,6 +1131,7 @@ _public_ int sd_event_add_io(
         if (!s)
                 return -ENOMEM;
 
+        s->wakeup = WAKEUP_EVENT_SOURCE;
         s->io.fd = fd;
         s->io.events = events;
         s->io.callback = callback;
@@ -870,7 +1174,7 @@ static int event_setup_timer_fd(
                 struct clock_data *d,
                 clockid_t clock) {
 
-        struct epoll_event ev = {};
+        struct epoll_event ev;
         int r, fd;
 
         assert(e);
@@ -883,8 +1187,12 @@ static int event_setup_timer_fd(
         if (fd < 0)
                 return -errno;
 
-        ev.events = EPOLLIN;
-        ev.data.ptr = INT_TO_PTR(clock_to_event_source_type(clock));
+        fd = fd_move_above_stdio(fd);
+
+        ev = (struct epoll_event) {
+                .events = EPOLLIN,
+                .data.ptr = d,
+        };
 
         r = epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, fd, &ev);
         if (r < 0) {
@@ -917,31 +1225,31 @@ _public_ int sd_event_add_time(
         int r;
 
         assert_return(e, -EINVAL);
-        assert_return(usec != (uint64_t) -1, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(accuracy != (uint64_t) -1, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
+        if (!clock_supported(clock)) /* Checks whether the kernel supports the clock */
+                return -EOPNOTSUPP;
+
+        type = clock_to_event_source_type(clock); /* checks whether sd-event supports this clock */
+        if (type < 0)
+                return -EOPNOTSUPP;
+
         if (!callback)
                 callback = time_exit_callback;
 
-        type = clock_to_event_source_type(clock);
-        assert_return(type >= 0, -EOPNOTSUPP);
-
         d = event_get_clock_data(e, type);
         assert(d);
 
-        if (!d->earliest) {
-                d->earliest = prioq_new(earliest_time_prioq_compare);
-                if (!d->earliest)
-                        return -ENOMEM;
-        }
+        r = prioq_ensure_allocated(&d->earliest, earliest_time_prioq_compare);
+        if (r < 0)
+                return r;
 
-        if (!d->latest) {
-                d->latest = prioq_new(latest_time_prioq_compare);
-                if (!d->latest)
-                        return -ENOMEM;
-        }
+        r = prioq_ensure_allocated(&d->latest, latest_time_prioq_compare);
+        if (r < 0)
+                return r;
 
         if (d->fd < 0) {
                 r = event_setup_timer_fd(e, d, clock);
@@ -994,13 +1302,13 @@ _public_ int sd_event_add_signal(
                 void *userdata) {
 
         sd_event_source *s;
+        struct signal_data *d;
         sigset_t ss;
         int r;
-        bool previous;
 
         assert_return(e, -EINVAL);
-        assert_return(sig > 0, -EINVAL);
-        assert_return(sig < _NSIG, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
+        assert_return(SIGNAL_VALID(sig), -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -1008,8 +1316,8 @@ _public_ int sd_event_add_signal(
                 callback = signal_exit_callback;
 
         r = pthread_sigmask(SIG_SETMASK, NULL, &ss);
-        if (r < 0)
-                return -errno;
+        if (r != 0)
+                return -r;
 
         if (!sigismember(&ss, sig))
                 return -EBUSY;
@@ -1021,8 +1329,6 @@ _public_ int sd_event_add_signal(
         } else if (e->signal_sources[sig])
                 return -EBUSY;
 
-        previous = need_signal(e, sig);
-
         s = source_new(e, !ret, SOURCE_SIGNAL);
         if (!s)
                 return -ENOMEM;
@@ -1034,14 +1340,10 @@ _public_ int sd_event_add_signal(
 
         e->signal_sources[sig] = s;
 
-        if (!previous) {
-                assert_se(sigaddset(&e->sigset, sig) == 0);
-
-                r = event_update_signal_fd(e);
-                if (r < 0) {
-                        source_free(s);
-                        return r;
-                }
+        r = event_make_signal_data(e, sig, &d);
+        if (r < 0) {
+                source_free(s);
+                return r;
         }
 
         /* Use the signal name as description for the event source by default */
@@ -1063,9 +1365,9 @@ _public_ int sd_event_add_child(
 
         sd_event_source *s;
         int r;
-        bool previous;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(pid > 1, -EINVAL);
         assert_return(!(options & ~(WEXITED|WSTOPPED|WCONTINUED)), -EINVAL);
         assert_return(options != 0, -EINVAL);
@@ -1077,11 +1379,9 @@ _public_ int sd_event_add_child(
         if (r < 0)
                 return r;
 
-        if (hashmap_contains(e->child_sources, INT_TO_PTR(pid)))
+        if (hashmap_contains(e->child_sources, PID_TO_PTR(pid)))
                 return -EBUSY;
 
-        previous = need_signal(e, SIGCHLD);
-
         s = source_new(e, !ret, SOURCE_CHILD);
         if (!s)
                 return -ENOMEM;
@@ -1092,22 +1392,19 @@ _public_ int sd_event_add_child(
         s->userdata = userdata;
         s->enabled = SD_EVENT_ONESHOT;
 
-        r = hashmap_put(e->child_sources, INT_TO_PTR(pid), s);
+        r = hashmap_put(e->child_sources, PID_TO_PTR(pid), s);
         if (r < 0) {
                 source_free(s);
                 return r;
         }
 
-        e->n_enabled_child_sources ++;
+        e->n_enabled_child_sources++;
 
-        if (!previous) {
-                assert_se(sigaddset(&e->sigset, SIGCHLD) == 0);
-
-                r = event_update_signal_fd(e);
-                if (r < 0) {
-                        source_free(s);
-                        return r;
-                }
+        r = event_make_signal_data(e, SIGCHLD, NULL);
+        if (r < 0) {
+                e->n_enabled_child_sources--;
+                source_free(s);
+                return r;
         }
 
         e->need_process_child = true;
@@ -1128,6 +1425,7 @@ _public_ int sd_event_add_defer(
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(callback, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
@@ -1162,6 +1460,7 @@ _public_ int sd_event_add_post(
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(callback, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
@@ -1200,15 +1499,14 @@ _public_ int sd_event_add_exit(
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(callback, -EINVAL);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
-        if (!e->exit) {
-                e->exit = prioq_new(exit_prioq_compare);
-                if (!e->exit)
-                        return -ENOMEM;
-        }
+        r = prioq_ensure_allocated(&e->exit, exit_prioq_compare);
+        if (r < 0)
+                return r;
 
         s = source_new(e, !ret, SOURCE_EXIT);
         if (!s)
@@ -1231,8 +1529,409 @@ _public_ int sd_event_add_exit(
         return 0;
 }
 
+static void event_free_inotify_data(sd_event *e, struct inotify_data *d) {
+        assert(e);
+
+        if (!d)
+                return;
+
+        assert(hashmap_isempty(d->inodes));
+        assert(hashmap_isempty(d->wd));
+
+        if (d->buffer_filled > 0)
+                LIST_REMOVE(buffered, e->inotify_data_buffered, d);
+
+        hashmap_free(d->inodes);
+        hashmap_free(d->wd);
+
+        assert_se(hashmap_remove(e->inotify_data, &d->priority) == d);
+
+        if (d->fd >= 0) {
+                if (epoll_ctl(e->epoll_fd, EPOLL_CTL_DEL, d->fd, NULL) < 0)
+                        log_debug_errno(errno, "Failed to remove inotify fd from epoll, ignoring: %m");
+
+                safe_close(d->fd);
+        }
+        free(d);
+}
+
+static int event_make_inotify_data(
+                sd_event *e,
+                int64_t priority,
+                struct inotify_data **ret) {
+
+        _cleanup_close_ int fd = -1;
+        struct inotify_data *d;
+        struct epoll_event ev;
+        int r;
+
+        assert(e);
+
+        d = hashmap_get(e->inotify_data, &priority);
+        if (d) {
+                if (ret)
+                        *ret = d;
+                return 0;
+        }
+
+        fd = inotify_init1(IN_NONBLOCK|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        fd = fd_move_above_stdio(fd);
+
+        r = hashmap_ensure_allocated(&e->inotify_data, &uint64_hash_ops);
+        if (r < 0)
+                return r;
+
+        d = new(struct inotify_data, 1);
+        if (!d)
+                return -ENOMEM;
+
+        *d = (struct inotify_data) {
+                .wakeup = WAKEUP_INOTIFY_DATA,
+                .fd = TAKE_FD(fd),
+                .priority = priority,
+        };
+
+        r = hashmap_put(e->inotify_data, &d->priority, d);
+        if (r < 0) {
+                d->fd = safe_close(d->fd);
+                free(d);
+                return r;
+        }
+
+        ev = (struct epoll_event) {
+                .events = EPOLLIN,
+                .data.ptr = d,
+        };
+
+        if (epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, d->fd, &ev) < 0) {
+                r = -errno;
+                d->fd = safe_close(d->fd); /* let's close this ourselves, as event_free_inotify_data() would otherwise
+                                            * remove the fd from the epoll first, which we don't want as we couldn't
+                                            * add it in the first place. */
+                event_free_inotify_data(e, d);
+                return r;
+        }
+
+        if (ret)
+                *ret = d;
+
+        return 1;
+}
+
+static int inode_data_compare(const void *a, const void *b) {
+        const struct inode_data *x = a, *y = b;
+
+        assert(x);
+        assert(y);
+
+        if (x->dev < y->dev)
+                return -1;
+        if (x->dev > y->dev)
+                return 1;
+
+        if (x->ino < y->ino)
+                return -1;
+        if (x->ino > y->ino)
+                return 1;
+
+        return 0;
+}
+
+static void inode_data_hash_func(const void *p, struct siphash *state) {
+        const struct inode_data *d = p;
+
+        assert(p);
+
+        siphash24_compress(&d->dev, sizeof(d->dev), state);
+        siphash24_compress(&d->ino, sizeof(d->ino), state);
+}
+
+const struct hash_ops inode_data_hash_ops = {
+        .hash = inode_data_hash_func,
+        .compare = inode_data_compare
+};
+
+static void event_free_inode_data(
+                sd_event *e,
+                struct inode_data *d) {
+
+        assert(e);
+
+        if (!d)
+                return;
+
+        assert(!d->event_sources);
+
+        if (d->fd >= 0) {
+                LIST_REMOVE(to_close, e->inode_data_to_close, d);
+                safe_close(d->fd);
+        }
+
+        if (d->inotify_data) {
+
+                if (d->wd >= 0) {
+                        if (d->inotify_data->fd >= 0) {
+                                /* So here's a problem. At the time this runs the watch descriptor might already be
+                                 * invalidated, because an IN_IGNORED event might be queued right the moment we enter
+                                 * the syscall. Hence, whenever we get EINVAL, ignore it entirely, since it's a very
+                                 * likely case to happen. */
+
+                                if (inotify_rm_watch(d->inotify_data->fd, d->wd) < 0 && errno != EINVAL)
+                                        log_debug_errno(errno, "Failed to remove watch descriptor %i from inotify, ignoring: %m", d->wd);
+                        }
+
+                        assert_se(hashmap_remove(d->inotify_data->wd, INT_TO_PTR(d->wd)) == d);
+                }
+
+                assert_se(hashmap_remove(d->inotify_data->inodes, d) == d);
+        }
+
+        free(d);
+}
+
+static void event_gc_inode_data(
+                sd_event *e,
+                struct inode_data *d) {
+
+        struct inotify_data *inotify_data;
+
+        assert(e);
+
+        if (!d)
+                return;
+
+        if (d->event_sources)
+                return;
+
+        inotify_data = d->inotify_data;
+        event_free_inode_data(e, d);
+
+        if (inotify_data && hashmap_isempty(inotify_data->inodes))
+                event_free_inotify_data(e, inotify_data);
+}
+
+static int event_make_inode_data(
+                sd_event *e,
+                struct inotify_data *inotify_data,
+                dev_t dev,
+                ino_t ino,
+                struct inode_data **ret) {
+
+        struct inode_data *d, key;
+        int r;
+
+        assert(e);
+        assert(inotify_data);
+
+        key = (struct inode_data) {
+                .ino = ino,
+                .dev = dev,
+        };
+
+        d = hashmap_get(inotify_data->inodes, &key);
+        if (d) {
+                if (ret)
+                        *ret = d;
+
+                return 0;
+        }
+
+        r = hashmap_ensure_allocated(&inotify_data->inodes, &inode_data_hash_ops);
+        if (r < 0)
+                return r;
+
+        d = new(struct inode_data, 1);
+        if (!d)
+                return -ENOMEM;
+
+        *d = (struct inode_data) {
+                .dev = dev,
+                .ino = ino,
+                .wd = -1,
+                .fd = -1,
+                .inotify_data = inotify_data,
+        };
+
+        r = hashmap_put(inotify_data->inodes, d, d);
+        if (r < 0) {
+                free(d);
+                return r;
+        }
+
+        if (ret)
+                *ret = d;
+
+        return 1;
+}
+
+static uint32_t inode_data_determine_mask(struct inode_data *d) {
+        bool excl_unlink = true;
+        uint32_t combined = 0;
+        sd_event_source *s;
+
+        assert(d);
+
+        /* Combines the watch masks of all event sources watching this inode. We generally just OR them together, but
+         * the IN_EXCL_UNLINK flag is ANDed instead.
+         *
+         * Note that we add all sources to the mask here, regardless whether enabled, disabled or oneshot. That's
+         * because we cannot change the mask anymore after the event source was created once, since the kernel has no
+         * API for that. Hence we need to subscribe to the maximum mask we ever might be interested in, and supress
+         * events we don't care for client-side. */
+
+        LIST_FOREACH(inotify.by_inode_data, s, d->event_sources) {
+
+                if ((s->inotify.mask & IN_EXCL_UNLINK) == 0)
+                        excl_unlink = false;
+
+                combined |= s->inotify.mask;
+        }
+
+        return (combined & ~(IN_ONESHOT|IN_DONT_FOLLOW|IN_ONLYDIR|IN_EXCL_UNLINK)) | (excl_unlink ? IN_EXCL_UNLINK : 0);
+}
+
+static int inode_data_realize_watch(sd_event *e, struct inode_data *d) {
+        uint32_t combined_mask;
+        int wd, r;
+
+        assert(d);
+        assert(d->fd >= 0);
+
+        combined_mask = inode_data_determine_mask(d);
+
+        if (d->wd >= 0 && combined_mask == d->combined_mask)
+                return 0;
+
+        r = hashmap_ensure_allocated(&d->inotify_data->wd, NULL);
+        if (r < 0)
+                return r;
+
+        wd = inotify_add_watch_fd(d->inotify_data->fd, d->fd, combined_mask);
+        if (wd < 0)
+                return -errno;
+
+        if (d->wd < 0) {
+                r = hashmap_put(d->inotify_data->wd, INT_TO_PTR(wd), d);
+                if (r < 0) {
+                        (void) inotify_rm_watch(d->inotify_data->fd, wd);
+                        return r;
+                }
+
+                d->wd = wd;
+
+        } else if (d->wd != wd) {
+
+                log_debug("Weird, the watch descriptor we already knew for this inode changed?");
+                (void) inotify_rm_watch(d->fd, wd);
+                return -EINVAL;
+        }
+
+        d->combined_mask = combined_mask;
+        return 1;
+}
+
+_public_ int sd_event_add_inotify(
+                sd_event *e,
+                sd_event_source **ret,
+                const char *path,
+                uint32_t mask,
+                sd_event_inotify_handler_t callback,
+                void *userdata) {
+
+        bool rm_inotify = false, rm_inode = false;
+        struct inotify_data *inotify_data = NULL;
+        struct inode_data *inode_data = NULL;
+        _cleanup_close_ int fd = -1;
+        sd_event_source *s;
+        struct stat st;
+        int r;
+
+        assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
+        assert_return(path, -EINVAL);
+        assert_return(callback, -EINVAL);
+        assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
+        assert_return(!event_pid_changed(e), -ECHILD);
+
+        /* Refuse IN_MASK_ADD since we coalesce watches on the same inode, and hence really don't want to merge
+         * masks. Or in other words, this whole code exists only to manage IN_MASK_ADD type operations for you, hence
+         * the user can't use them for us. */
+        if (mask & IN_MASK_ADD)
+                return -EINVAL;
+
+        fd = open(path, O_PATH|O_CLOEXEC|
+                  (mask & IN_ONLYDIR ? O_DIRECTORY : 0)|
+                  (mask & IN_DONT_FOLLOW ? O_NOFOLLOW : 0));
+        if (fd < 0)
+                return -errno;
+
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        s = source_new(e, !ret, SOURCE_INOTIFY);
+        if (!s)
+                return -ENOMEM;
+
+        s->enabled = mask & IN_ONESHOT ? SD_EVENT_ONESHOT : SD_EVENT_ON;
+        s->inotify.mask = mask;
+        s->inotify.callback = callback;
+        s->userdata = userdata;
+
+        /* Allocate an inotify object for this priority, and an inode object within it */
+        r = event_make_inotify_data(e, SD_EVENT_PRIORITY_NORMAL, &inotify_data);
+        if (r < 0)
+                goto fail;
+        rm_inotify = r > 0;
+
+        r = event_make_inode_data(e, inotify_data, st.st_dev, st.st_ino, &inode_data);
+        if (r < 0)
+                goto fail;
+        rm_inode = r > 0;
+
+        /* Keep the O_PATH fd around until the first iteration of the loop, so that we can still change the priority of
+         * the event source, until then, for which we need the original inode. */
+        if (inode_data->fd < 0) {
+                inode_data->fd = TAKE_FD(fd);
+                LIST_PREPEND(to_close, e->inode_data_to_close, inode_data);
+        }
+
+        /* Link our event source to the inode data object */
+        LIST_PREPEND(inotify.by_inode_data, inode_data->event_sources, s);
+        s->inotify.inode_data = inode_data;
+
+        rm_inode = rm_inotify = false;
+
+        /* Actually realize the watch now */
+        r = inode_data_realize_watch(e, inode_data);
+        if (r < 0)
+                goto fail;
+
+        (void) sd_event_source_set_description(s, path);
+
+        if (ret)
+                *ret = s;
+
+        return 0;
+
+fail:
+        source_free(s);
+
+        if (rm_inode)
+                event_free_inode_data(e, inode_data);
+
+        if (rm_inotify)
+                event_free_inotify_data(e, inotify_data);
+
+        return r;
+}
+
 _public_ sd_event_source* sd_event_source_ref(sd_event_source *s) {
-        assert_return(s, NULL);
+
+        if (!s)
+                return NULL;
 
         assert(s->n_ref >= 1);
         s->n_ref++;
@@ -1313,7 +2012,7 @@ _public_ int sd_event_source_set_io_fd(sd_event_source *s, int fd) {
         int r;
 
         assert_return(s, -EINVAL);
-        assert_return(fd >= 0, -EINVAL);
+        assert_return(fd >= 0, -EBADF);
         assert_return(s->type == SOURCE_IO, -EDOM);
         assert_return(!event_pid_changed(s->event), -ECHILD);
 
@@ -1345,6 +2044,21 @@ _public_ int sd_event_source_set_io_fd(sd_event_source *s, int fd) {
         return 0;
 }
 
+_public_ int sd_event_source_get_io_fd_own(sd_event_source *s) {
+        assert_return(s, -EINVAL);
+        assert_return(s->type == SOURCE_IO, -EDOM);
+
+        return s->io.owned;
+}
+
+_public_ int sd_event_source_set_io_fd_own(sd_event_source *s, int own) {
+        assert_return(s, -EINVAL);
+        assert_return(s->type == SOURCE_IO, -EDOM);
+
+        s->io.owned = own;
+        return 0;
+}
+
 _public_ int sd_event_source_get_io_events(sd_event_source *s, uint32_t* events) {
         assert_return(s, -EINVAL);
         assert_return(events, -EINVAL);
@@ -1368,6 +2082,10 @@ _public_ int sd_event_source_set_io_events(sd_event_source *s, uint32_t events)
         if (s->io.events == events && !(events & EPOLLET))
                 return 0;
 
+        r = source_set_pending(s, false);
+        if (r < 0)
+                return r;
+
         if (s->enabled != SD_EVENT_OFF) {
                 r = source_io_register(s, s->enabled, events);
                 if (r < 0)
@@ -1375,7 +2093,6 @@ _public_ int sd_event_source_set_io_events(sd_event_source *s, uint32_t events)
         }
 
         s->io.events = events;
-        source_set_pending(s, false);
 
         return 0;
 }
@@ -1396,25 +2113,101 @@ _public_ int sd_event_source_get_signal(sd_event_source *s) {
         assert_return(s->type == SOURCE_SIGNAL, -EDOM);
         assert_return(!event_pid_changed(s->event), -ECHILD);
 
-        return s->signal.sig;
-}
+        return s->signal.sig;
+}
+
+_public_ int sd_event_source_get_priority(sd_event_source *s, int64_t *priority) {
+        assert_return(s, -EINVAL);
+        assert_return(!event_pid_changed(s->event), -ECHILD);
+
+        *priority = s->priority;
+        return 0;
+}
+
+_public_ int sd_event_source_set_priority(sd_event_source *s, int64_t priority) {
+        bool rm_inotify = false, rm_inode = false;
+        struct inotify_data *new_inotify_data = NULL;
+        struct inode_data *new_inode_data = NULL;
+        int r;
+
+        assert_return(s, -EINVAL);
+        assert_return(s->event->state != SD_EVENT_FINISHED, -ESTALE);
+        assert_return(!event_pid_changed(s->event), -ECHILD);
+
+        if (s->priority == priority)
+                return 0;
+
+        if (s->type == SOURCE_INOTIFY) {
+                struct inode_data *old_inode_data;
+
+                assert(s->inotify.inode_data);
+                old_inode_data = s->inotify.inode_data;
+
+                /* We need the original fd to change the priority. If we don't have it we can't change the priority,
+                 * anymore. Note that we close any fds when entering the next event loop iteration, i.e. for inotify
+                 * events we allow priority changes only until the first following iteration. */
+                if (old_inode_data->fd < 0)
+                        return -EOPNOTSUPP;
+
+                r = event_make_inotify_data(s->event, priority, &new_inotify_data);
+                if (r < 0)
+                        return r;
+                rm_inotify = r > 0;
+
+                r = event_make_inode_data(s->event, new_inotify_data, old_inode_data->dev, old_inode_data->ino, &new_inode_data);
+                if (r < 0)
+                        goto fail;
+                rm_inode = r > 0;
+
+                if (new_inode_data->fd < 0) {
+                        /* Duplicate the fd for the new inode object if we don't have any yet */
+                        new_inode_data->fd = fcntl(old_inode_data->fd, F_DUPFD_CLOEXEC, 3);
+                        if (new_inode_data->fd < 0) {
+                                r = -errno;
+                                goto fail;
+                        }
+
+                        LIST_PREPEND(to_close, s->event->inode_data_to_close, new_inode_data);
+                }
+
+                /* Move the event source to the new inode data structure */
+                LIST_REMOVE(inotify.by_inode_data, old_inode_data->event_sources, s);
+                LIST_PREPEND(inotify.by_inode_data, new_inode_data->event_sources, s);
+                s->inotify.inode_data = new_inode_data;
+
+                /* Now create the new watch */
+                r = inode_data_realize_watch(s->event, new_inode_data);
+                if (r < 0) {
+                        /* Move it back */
+                        LIST_REMOVE(inotify.by_inode_data, new_inode_data->event_sources, s);
+                        LIST_PREPEND(inotify.by_inode_data, old_inode_data->event_sources, s);
+                        s->inotify.inode_data = old_inode_data;
+                        goto fail;
+                }
+
+                s->priority = priority;
 
-_public_ int sd_event_source_get_priority(sd_event_source *s, int64_t *priority) {
-        assert_return(s, -EINVAL);
-        assert_return(!event_pid_changed(s->event), -ECHILD);
+                event_gc_inode_data(s->event, old_inode_data);
 
-        return s->priority;
-}
+        } else if (s->type == SOURCE_SIGNAL && s->enabled != SD_EVENT_OFF) {
+                struct signal_data *old, *d;
 
-_public_ int sd_event_source_set_priority(sd_event_source *s, int64_t priority) {
-        assert_return(s, -EINVAL);
-        assert_return(s->event->state != SD_EVENT_FINISHED, -ESTALE);
-        assert_return(!event_pid_changed(s->event), -ECHILD);
+                /* Move us from the signalfd belonging to the old
+                 * priority to the signalfd of the new priority */
 
-        if (s->priority == priority)
-                return 0;
+                assert_se(old = hashmap_get(s->event->signal_data, &s->priority));
+
+                s->priority = priority;
+
+                r = event_make_signal_data(s->event, s->signal.sig, &d);
+                if (r < 0) {
+                        s->priority = old->priority;
+                        return r;
+                }
 
-        s->priority = priority;
+                event_unmask_signal_data(s->event, old, s->signal.sig);
+        } else
+                s->priority = priority;
 
         if (s->pending)
                 prioq_reshuffle(s->event->pending, s, &s->pending_index);
@@ -1426,6 +2219,15 @@ _public_ int sd_event_source_set_priority(sd_event_source *s, int64_t priority)
                 prioq_reshuffle(s->event->exit, s, &s->exit.prioq_index);
 
         return 0;
+
+fail:
+        if (rm_inode)
+                event_free_inode_data(s->event, new_inode_data);
+
+        if (rm_inotify)
+                event_free_inotify_data(s->event, new_inotify_data);
+
+        return r;
 }
 
 _public_ int sd_event_source_get_enabled(sd_event_source *s, int *m) {
@@ -1441,7 +2243,7 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
         int r;
 
         assert_return(s, -EINVAL);
-        assert_return(m == SD_EVENT_OFF || m == SD_EVENT_ON || m == SD_EVENT_ONESHOT, -EINVAL);
+        assert_return(IN_SET(m, SD_EVENT_OFF, SD_EVENT_ON, SD_EVENT_ONESHOT), -EINVAL);
         assert_return(!event_pid_changed(s->event), -ECHILD);
 
         /* If we are dead anyway, we are fine with turning off
@@ -1454,13 +2256,17 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
 
         if (m == SD_EVENT_OFF) {
 
-                switch (s->type) {
-
-                case SOURCE_IO:
-                        r = source_io_unregister(s);
+                /* Unset the pending flag when this event source is disabled */
+                if (!IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
+                        r = source_set_pending(s, false);
                         if (r < 0)
                                 return r;
+                }
+
+                switch (s->type) {
 
+                case SOURCE_IO:
+                        source_io_unregister(s);
                         s->enabled = m;
                         break;
 
@@ -1482,34 +2288,18 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
                 }
 
                 case SOURCE_SIGNAL:
-                        assert(need_signal(s->event, s->signal.sig));
-
                         s->enabled = m;
 
-                        if (!need_signal(s->event, s->signal.sig)) {
-                                assert_se(sigdelset(&s->event->sigset, s->signal.sig) == 0);
-
-                                (void) event_update_signal_fd(s->event);
-                                /* If disabling failed, we might get a spurious event,
-                                 * but otherwise nothing bad should happen. */
-                        }
-
+                        event_gc_signal_data(s->event, &s->priority, s->signal.sig);
                         break;
 
                 case SOURCE_CHILD:
-                        assert(need_signal(s->event, SIGCHLD));
-
                         s->enabled = m;
 
                         assert(s->event->n_enabled_child_sources > 0);
                         s->event->n_enabled_child_sources--;
 
-                        if (!need_signal(s->event, SIGCHLD)) {
-                                assert_se(sigdelset(&s->event->sigset, SIGCHLD) == 0);
-
-                                (void) event_update_signal_fd(s->event);
-                        }
-
+                        event_gc_signal_data(s->event, &s->priority, SIGCHLD);
                         break;
 
                 case SOURCE_EXIT:
@@ -1519,6 +2309,7 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
 
                 case SOURCE_DEFER:
                 case SOURCE_POST:
+                case SOURCE_INOTIFY:
                         s->enabled = m;
                         break;
 
@@ -1527,6 +2318,14 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
                 }
 
         } else {
+
+                /* Unset the pending flag when this event source is enabled */
+                if (s->enabled == SD_EVENT_OFF && !IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
+                        r = source_set_pending(s, false);
+                        if (r < 0)
+                                return r;
+                }
+
                 switch (s->type) {
 
                 case SOURCE_IO:
@@ -1555,37 +2354,33 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
                 }
 
                 case SOURCE_SIGNAL:
-                        /* Check status before enabling. */
-                        if (!need_signal(s->event, s->signal.sig)) {
-                                assert_se(sigaddset(&s->event->sigset, s->signal.sig) == 0);
 
-                                r = event_update_signal_fd(s->event);
-                                if (r < 0) {
-                                        s->enabled = SD_EVENT_OFF;
-                                        return r;
-                                }
+                        s->enabled = m;
+
+                        r = event_make_signal_data(s->event, s->signal.sig, NULL);
+                        if (r < 0) {
+                                s->enabled = SD_EVENT_OFF;
+                                event_gc_signal_data(s->event, &s->priority, s->signal.sig);
+                                return r;
                         }
 
-                        s->enabled = m;
                         break;
 
                 case SOURCE_CHILD:
-                        /* Check status before enabling. */
-                        if (s->enabled == SD_EVENT_OFF) {
-                                if (!need_signal(s->event, SIGCHLD)) {
-                                        assert_se(sigaddset(&s->event->sigset, s->signal.sig) == 0);
-
-                                        r = event_update_signal_fd(s->event);
-                                        if (r < 0) {
-                                                s->enabled = SD_EVENT_OFF;
-                                                return r;
-                                        }
-                                }
 
+                        if (s->enabled == SD_EVENT_OFF)
                                 s->event->n_enabled_child_sources++;
-                        }
 
                         s->enabled = m;
+
+                        r = event_make_signal_data(s->event, SIGCHLD, NULL);
+                        if (r < 0) {
+                                s->enabled = SD_EVENT_OFF;
+                                s->event->n_enabled_child_sources--;
+                                event_gc_signal_data(s->event, &s->priority, SIGCHLD);
+                                return r;
+                        }
+
                         break;
 
                 case SOURCE_EXIT:
@@ -1595,6 +2390,7 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
 
                 case SOURCE_DEFER:
                 case SOURCE_POST:
+                case SOURCE_INOTIFY:
                         s->enabled = m;
                         break;
 
@@ -1624,16 +2420,18 @@ _public_ int sd_event_source_get_time(sd_event_source *s, uint64_t *usec) {
 
 _public_ int sd_event_source_set_time(sd_event_source *s, uint64_t usec) {
         struct clock_data *d;
+        int r;
 
         assert_return(s, -EINVAL);
-        assert_return(usec != (uint64_t) -1, -EINVAL);
         assert_return(EVENT_SOURCE_IS_TIME(s->type), -EDOM);
         assert_return(s->event->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(s->event), -ECHILD);
 
-        s->time.next = usec;
+        r = source_set_pending(s, false);
+        if (r < 0)
+                return r;
 
-        source_set_pending(s, false);
+        s->time.next = usec;
 
         d = event_get_clock_data(s->event, s->type);
         assert(d);
@@ -1657,6 +2455,7 @@ _public_ int sd_event_source_get_time_accuracy(sd_event_source *s, uint64_t *use
 
 _public_ int sd_event_source_set_time_accuracy(sd_event_source *s, uint64_t usec) {
         struct clock_data *d;
+        int r;
 
         assert_return(s, -EINVAL);
         assert_return(usec != (uint64_t) -1, -EINVAL);
@@ -1664,13 +2463,15 @@ _public_ int sd_event_source_set_time_accuracy(sd_event_source *s, uint64_t usec
         assert_return(s->event->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(s->event), -ECHILD);
 
+        r = source_set_pending(s, false);
+        if (r < 0)
+                return r;
+
         if (usec == 0)
                 usec = DEFAULT_ACCURACY_USEC;
 
         s->time.accuracy = usec;
 
-        source_set_pending(s, false);
-
         d = event_get_clock_data(s->event, s->type);
         assert(d);
 
@@ -1700,6 +2501,16 @@ _public_ int sd_event_source_get_child_pid(sd_event_source *s, pid_t *pid) {
         return 0;
 }
 
+_public_ int sd_event_source_get_inotify_mask(sd_event_source *s, uint32_t *mask) {
+        assert_return(s, -EINVAL);
+        assert_return(mask, -EINVAL);
+        assert_return(s->type == SOURCE_INOTIFY, -EDOM);
+        assert_return(!event_pid_changed(s->event), -ECHILD);
+
+        *mask = s->inotify.mask;
+        return 0;
+}
+
 _public_ int sd_event_source_set_prepare(sd_event_source *s, sd_event_handler_t callback) {
         int r;
 
@@ -1756,6 +2567,8 @@ static usec_t sleep_between(sd_event *e, usec_t a, usec_t b) {
 
         if (a <= 0)
                 return 0;
+        if (a >= USEC_INFINITY)
+                return USEC_INFINITY;
 
         if (b <= a + 1)
                 return a;
@@ -1845,7 +2658,7 @@ static int event_arm_timer(
                 d->needs_rearm = false;
 
         a = prioq_peek(d->earliest);
-        if (!a || a->enabled == SD_EVENT_OFF) {
+        if (!a || a->enabled == SD_EVENT_OFF || a->time.next == USEC_INFINITY) {
 
                 if (d->fd < 0)
                         return 0;
@@ -1865,7 +2678,7 @@ static int event_arm_timer(
         b = prioq_peek(d->latest);
         assert_se(b && b->enabled != SD_EVENT_OFF);
 
-        t = sleep_between(e, a->time.next, b->time.next + b->time.accuracy);
+        t = sleep_between(e, a->time.next, time_event_source_latest(b));
         if (d->next == t)
                 return 0;
 
@@ -1916,7 +2729,7 @@ static int flush_timer(sd_event *e, int fd, uint32_t events, usec_t *next) {
 
         ss = read(fd, &x, sizeof(x));
         if (ss < 0) {
-                if (errno == EAGAIN || errno == EINTR)
+                if (IN_SET(errno, EAGAIN, EINTR))
                         return 0;
 
                 return -errno;
@@ -2005,10 +2818,7 @@ static int process_child(sd_event *e) {
                         return -errno;
 
                 if (s->child.siginfo.si_pid != 0) {
-                        bool zombie =
-                                s->child.siginfo.si_code == CLD_EXITED ||
-                                s->child.siginfo.si_code == CLD_KILLED ||
-                                s->child.siginfo.si_code == CLD_DUMPED;
+                        bool zombie = IN_SET(s->child.siginfo.si_code, CLD_EXITED, CLD_KILLED, CLD_DUMPED);
 
                         if (!zombie && (s->child.options & WEXITED)) {
                                 /* If the child isn't dead then let's
@@ -2029,22 +2839,38 @@ static int process_child(sd_event *e) {
         return 0;
 }
 
-static int process_signal(sd_event *e, uint32_t events) {
+static int process_signal(sd_event *e, struct signal_data *d, uint32_t events) {
         bool read_one = false;
         int r;
 
         assert(e);
-
+        assert(d);
         assert_return(events == EPOLLIN, -EIO);
 
+        /* If there's a signal queued on this priority and SIGCHLD is
+           on this priority too, then make sure to recheck the
+           children we watch. This is because we only ever dequeue
+           the first signal per priority, and if we dequeue one, and
+           SIGCHLD might be enqueued later we wouldn't know, but we
+           might have higher priority children we care about hence we
+           need to check that explicitly. */
+
+        if (sigismember(&d->sigset, SIGCHLD))
+                e->need_process_child = true;
+
+        /* If there's already an event source pending for this
+         * priority we don't read another */
+        if (d->current)
+                return 0;
+
         for (;;) {
                 struct signalfd_siginfo si;
                 ssize_t n;
                 sd_event_source *s = NULL;
 
-                n = read(e->signal_fd, &si, sizeof(si));
+                n = read(d->fd, &si, sizeof(si));
                 if (n < 0) {
-                        if (errno == EAGAIN || errno == EINTR)
+                        if (IN_SET(errno, EAGAIN, EINTR))
                                 return read_one;
 
                         return -errno;
@@ -2053,38 +2879,194 @@ static int process_signal(sd_event *e, uint32_t events) {
                 if (_unlikely_(n != sizeof(si)))
                         return -EIO;
 
-                assert(si.ssi_signo < _NSIG);
+                assert(SIGNAL_VALID(si.ssi_signo));
 
                 read_one = true;
 
-                if (si.ssi_signo == SIGCHLD) {
-                        r = process_child(e);
-                        if (r < 0)
-                                return r;
-                        if (r > 0)
-                                continue;
-                }
-
                 if (e->signal_sources)
                         s = e->signal_sources[si.ssi_signo];
-
                 if (!s)
                         continue;
+                if (s->pending)
+                        continue;
 
                 s->signal.siginfo = si;
+                d->current = s;
+
                 r = source_set_pending(s, true);
                 if (r < 0)
                         return r;
+
+                return 1;
+        }
+}
+
+static int event_inotify_data_read(sd_event *e, struct inotify_data *d, uint32_t revents) {
+        ssize_t n;
+
+        assert(e);
+        assert(d);
+
+        assert_return(revents == EPOLLIN, -EIO);
+
+        /* If there's already an event source pending for this priority, don't read another */
+        if (d->n_pending > 0)
+                return 0;
+
+        /* Is the read buffer non-empty? If so, let's not read more */
+        if (d->buffer_filled > 0)
+                return 0;
+
+        n = read(d->fd, &d->buffer, sizeof(d->buffer));
+        if (n < 0) {
+                if (IN_SET(errno, EAGAIN, EINTR))
+                        return 0;
+
+                return -errno;
+        }
+
+        assert(n > 0);
+        d->buffer_filled = (size_t) n;
+        LIST_PREPEND(buffered, e->inotify_data_buffered, d);
+
+        return 1;
+}
+
+static void event_inotify_data_drop(sd_event *e, struct inotify_data *d, size_t sz) {
+        assert(e);
+        assert(d);
+        assert(sz <= d->buffer_filled);
+
+        if (sz == 0)
+                return;
+
+        /* Move the rest to the buffer to the front, in order to get things properly aligned again */
+        memmove(d->buffer.raw, d->buffer.raw + sz, d->buffer_filled - sz);
+        d->buffer_filled -= sz;
+
+        if (d->buffer_filled == 0)
+                LIST_REMOVE(buffered, e->inotify_data_buffered, d);
+}
+
+static int event_inotify_data_process(sd_event *e, struct inotify_data *d) {
+        int r;
+
+        assert(e);
+        assert(d);
+
+        /* If there's already an event source pending for this priority, don't read another */
+        if (d->n_pending > 0)
+                return 0;
+
+        while (d->buffer_filled > 0) {
+                size_t sz;
+
+                /* Let's validate that the event structures are complete */
+                if (d->buffer_filled < offsetof(struct inotify_event, name))
+                        return -EIO;
+
+                sz = offsetof(struct inotify_event, name) + d->buffer.ev.len;
+                if (d->buffer_filled < sz)
+                        return -EIO;
+
+                if (d->buffer.ev.mask & IN_Q_OVERFLOW) {
+                        struct inode_data *inode_data;
+                        Iterator i;
+
+                        /* The queue overran, let's pass this event to all event sources connected to this inotify
+                         * object */
+
+                        HASHMAP_FOREACH(inode_data, d->inodes, i) {
+                                sd_event_source *s;
+
+                                LIST_FOREACH(inotify.by_inode_data, s, inode_data->event_sources) {
+
+                                        if (s->enabled == SD_EVENT_OFF)
+                                                continue;
+
+                                        r = source_set_pending(s, true);
+                                        if (r < 0)
+                                                return r;
+                                }
+                        }
+                } else {
+                        struct inode_data *inode_data;
+                        sd_event_source *s;
+
+                        /* Find the inode object for this watch descriptor. If IN_IGNORED is set we also remove it from
+                         * our watch descriptor table. */
+                        if (d->buffer.ev.mask & IN_IGNORED) {
+
+                                inode_data = hashmap_remove(d->wd, INT_TO_PTR(d->buffer.ev.wd));
+                                if (!inode_data) {
+                                        event_inotify_data_drop(e, d, sz);
+                                        continue;
+                                }
+
+                                /* The watch descriptor was removed by the kernel, let's drop it here too */
+                                inode_data->wd = -1;
+                        } else {
+                                inode_data = hashmap_get(d->wd, INT_TO_PTR(d->buffer.ev.wd));
+                                if (!inode_data) {
+                                        event_inotify_data_drop(e, d, sz);
+                                        continue;
+                                }
+                        }
+
+                        /* Trigger all event sources that are interested in these events. Also trigger all event
+                         * sources if IN_IGNORED or IN_UNMOUNT is set. */
+                        LIST_FOREACH(inotify.by_inode_data, s, inode_data->event_sources) {
+
+                                if (s->enabled == SD_EVENT_OFF)
+                                        continue;
+
+                                if ((d->buffer.ev.mask & (IN_IGNORED|IN_UNMOUNT)) == 0 &&
+                                    (s->inotify.mask & d->buffer.ev.mask & IN_ALL_EVENTS) == 0)
+                                        continue;
+
+                                r = source_set_pending(s, true);
+                                if (r < 0)
+                                        return r;
+                        }
+                }
+
+                /* Something pending now? If so, let's finish, otherwise let's read more. */
+                if (d->n_pending > 0)
+                        return 1;
+        }
+
+        return 0;
+}
+
+static int process_inotify(sd_event *e) {
+        struct inotify_data *d;
+        int r, done = 0;
+
+        assert(e);
+
+        LIST_FOREACH(buffered, d, e->inotify_data_buffered) {
+                r = event_inotify_data_process(e, d);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        done ++;
         }
+
+        return done;
 }
 
 static int source_dispatch(sd_event_source *s) {
+        EventSourceType saved_type;
         int r = 0;
 
         assert(s);
         assert(s->pending || s->type == SOURCE_EXIT);
 
-        if (s->type != SOURCE_DEFER && s->type != SOURCE_EXIT) {
+        /* Save the event source type, here, so that we still know it after the event callback which might invalidate
+         * the event. */
+        saved_type = s->type;
+
+        if (!IN_SET(s->type, SOURCE_DEFER, SOURCE_EXIT)) {
                 r = source_set_pending(s, false);
                 if (r < 0)
                         return r;
@@ -2136,15 +3118,13 @@ static int source_dispatch(sd_event_source *s) {
         case SOURCE_CHILD: {
                 bool zombie;
 
-                zombie = s->child.siginfo.si_code == CLD_EXITED ||
-                         s->child.siginfo.si_code == CLD_KILLED ||
-                         s->child.siginfo.si_code == CLD_DUMPED;
+                zombie = IN_SET(s->child.siginfo.si_code, CLD_EXITED, CLD_KILLED, CLD_DUMPED);
 
                 r = s->child.callback(s, &s->child.siginfo, s->userdata);
 
                 /* Now, reap the PID for good. */
                 if (zombie)
-                        waitid(P_PID, s->child.pid, &s->child.siginfo, WNOHANG|WEXITED);
+                        (void) waitid(P_PID, s->child.pid, &s->child.siginfo, WNOHANG|WEXITED);
 
                 break;
         }
@@ -2161,6 +3141,28 @@ static int source_dispatch(sd_event_source *s) {
                 r = s->exit.callback(s, s->userdata);
                 break;
 
+        case SOURCE_INOTIFY: {
+                struct sd_event *e = s->event;
+                struct inotify_data *d;
+                size_t sz;
+
+                assert(s->inotify.inode_data);
+                assert_se(d = s->inotify.inode_data->inotify_data);
+
+                assert(d->buffer_filled >= offsetof(struct inotify_event, name));
+                sz = offsetof(struct inotify_event, name) + d->buffer.ev.len;
+                assert(d->buffer_filled >= sz);
+
+                r = s->inotify.callback(s, &d->buffer.ev, s->userdata);
+
+                /* When no event is pending anymore on this inotify object, then let's drop the event from the
+                 * buffer. */
+                if (d->n_pending == 0)
+                        event_inotify_data_drop(e, d, sz);
+
+                break;
+        }
+
         case SOURCE_WATCHDOG:
         case _SOURCE_EVENT_SOURCE_TYPE_MAX:
         case _SOURCE_EVENT_SOURCE_TYPE_INVALID:
@@ -2169,12 +3171,9 @@ static int source_dispatch(sd_event_source *s) {
 
         s->dispatching = false;
 
-        if (r < 0) {
-                if (s->description)
-                        log_debug_errno(r, "Event source '%s' returned error, disabling: %m", s->description);
-                else
-                        log_debug_errno(r, "Event source %p returned error, disabling: %m", s);
-        }
+        if (r < 0)
+                log_debug_errno(r, "Event source %s (type %s) returned error, disabling: %m",
+                                strna(s->description), event_source_type_to_string(saved_type));
 
         if (s->n_ref == 0)
                 source_free(s);
@@ -2207,12 +3206,9 @@ static int event_prepare(sd_event *e) {
                 r = s->prepare(s, s->userdata);
                 s->dispatching = false;
 
-                if (r < 0) {
-                        if (s->description)
-                                log_debug_errno(r, "Prepare callback of event source '%s' returned error, disabling: %m", s->description);
-                        else
-                                log_debug_errno(r, "Prepare callback of event source %p returned error, disabling: %m", s);
-                }
+                if (r < 0)
+                        log_debug_errno(r, "Prepare callback of event source %s (type %s) returned error, disabling: %m",
+                                        strna(s->description), event_source_type_to_string(s->type));
 
                 if (s->n_ref == 0)
                         source_free(s);
@@ -2225,6 +3221,7 @@ static int event_prepare(sd_event *e) {
 
 static int dispatch_exit(sd_event *e) {
         sd_event_source *p;
+        _cleanup_(sd_event_unrefp) sd_event *ref = NULL;
         int r;
 
         assert(e);
@@ -2235,15 +3232,11 @@ static int dispatch_exit(sd_event *e) {
                 return 0;
         }
 
-        sd_event_ref(e);
+        ref = sd_event_ref(e);
         e->iteration++;
         e->state = SD_EVENT_EXITING;
-
         r = source_dispatch(p);
-
         e->state = SD_EVENT_INITIAL;
-        sd_event_unref(e);
-
         return r;
 }
 
@@ -2304,10 +3297,30 @@ static int process_watchdog(sd_event *e) {
         return arm_watchdog(e);
 }
 
+static void event_close_inode_data_fds(sd_event *e) {
+        struct inode_data *d;
+
+        assert(e);
+
+        /* Close the fds pointing to the inodes to watch now. We need to close them as they might otherwise pin
+         * filesystems. But we can't close them right-away as we need them as long as the user still wants to make
+         * adjustments to the even source, such as changing the priority (which requires us to remove and readd a watch
+         * for the inode). Hence, let's close them when entering the first iteration after they were added, as a
+         * compromise. */
+
+        while ((d = e->inode_data_to_close)) {
+                assert(d->fd >= 0);
+                d->fd = safe_close(d->fd);
+
+                LIST_REMOVE(to_close, e->inode_data_to_close, d);
+        }
+}
+
 _public_ int sd_event_prepare(sd_event *e) {
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(e->state == SD_EVENT_INITIAL, -EBUSY);
@@ -2317,7 +3330,9 @@ _public_ int sd_event_prepare(sd_event *e) {
 
         e->iteration++;
 
+        e->state = SD_EVENT_PREPARING;
         r = event_prepare(e);
+        e->state = SD_EVENT_INITIAL;
         if (r < 0)
                 return r;
 
@@ -2341,6 +3356,8 @@ _public_ int sd_event_prepare(sd_event *e) {
         if (r < 0)
                 return r;
 
+        event_close_inode_data_fds(e);
+
         if (event_next_pending(e) || e->need_process_child)
                 goto pending;
 
@@ -2363,6 +3380,7 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {
         int r, m, i;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(e->state == SD_EVENT_ARMED, -EBUSY);
@@ -2375,6 +3393,10 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {
         ev_queue_max = MAX(e->n_sources, 1u);
         ev_queue = newa(struct epoll_event, ev_queue_max);
 
+        /* If we still have inotify data buffered, then query the other fds, but don't wait on it */
+        if (e->inotify_data_buffered)
+                timeout = 0;
+
         m = epoll_wait(e->epoll_fd, ev_queue, ev_queue_max,
                        timeout == (uint64_t) -1 ? -1 : (int) ((timeout + USEC_PER_MSEC - 1) / USEC_PER_MSEC));
         if (m < 0) {
@@ -2384,32 +3406,42 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {
                 }
 
                 r = -errno;
-
                 goto finish;
         }
 
-        dual_timestamp_get(&e->timestamp);
-        e->timestamp_boottime = now(CLOCK_BOOTTIME);
+        triple_timestamp_get(&e->timestamp);
 
         for (i = 0; i < m; i++) {
 
-                if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_TIME_REALTIME))
-                        r = flush_timer(e, e->realtime.fd, ev_queue[i].events, &e->realtime.next);
-                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_TIME_BOOTTIME))
-                        r = flush_timer(e, e->boottime.fd, ev_queue[i].events, &e->boottime.next);
-                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_TIME_MONOTONIC))
-                        r = flush_timer(e, e->monotonic.fd, ev_queue[i].events, &e->monotonic.next);
-                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_TIME_REALTIME_ALARM))
-                        r = flush_timer(e, e->realtime_alarm.fd, ev_queue[i].events, &e->realtime_alarm.next);
-                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_TIME_BOOTTIME_ALARM))
-                        r = flush_timer(e, e->boottime_alarm.fd, ev_queue[i].events, &e->boottime_alarm.next);
-                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_SIGNAL))
-                        r = process_signal(e, ev_queue[i].events);
-                else if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_WATCHDOG))
+                if (ev_queue[i].data.ptr == INT_TO_PTR(SOURCE_WATCHDOG))
                         r = flush_timer(e, e->watchdog_fd, ev_queue[i].events, NULL);
-                else
-                        r = process_io(e, ev_queue[i].data.ptr, ev_queue[i].events);
+                else {
+                        WakeupType *t = ev_queue[i].data.ptr;
+
+                        switch (*t) {
+
+                        case WAKEUP_EVENT_SOURCE:
+                                r = process_io(e, ev_queue[i].data.ptr, ev_queue[i].events);
+                                break;
+
+                        case WAKEUP_CLOCK_DATA: {
+                                struct clock_data *d = ev_queue[i].data.ptr;
+                                r = flush_timer(e, d->fd, ev_queue[i].events, &d->next);
+                                break;
+                        }
+
+                        case WAKEUP_SIGNAL_DATA:
+                                r = process_signal(e, ev_queue[i].data.ptr, ev_queue[i].events);
+                                break;
 
+                        case WAKEUP_INOTIFY_DATA:
+                                r = event_inotify_data_read(e, ev_queue[i].data.ptr, ev_queue[i].events);
+                                break;
+
+                        default:
+                                assert_not_reached("Invalid wake-up pointer");
+                        }
+                }
                 if (r < 0)
                         goto finish;
         }
@@ -2422,7 +3454,7 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {
         if (r < 0)
                 goto finish;
 
-        r = process_timer(e, e->timestamp_boottime, &e->boottime);
+        r = process_timer(e, e->timestamp.boottime, &e->boottime);
         if (r < 0)
                 goto finish;
 
@@ -2434,7 +3466,7 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {
         if (r < 0)
                 goto finish;
 
-        r = process_timer(e, e->timestamp_boottime, &e->boottime_alarm);
+        r = process_timer(e, e->timestamp.boottime, &e->boottime_alarm);
         if (r < 0)
                 goto finish;
 
@@ -2444,6 +3476,10 @@ _public_ int sd_event_wait(sd_event *e, uint64_t timeout) {
                         goto finish;
         }
 
+        r = process_inotify(e);
+        if (r < 0)
+                goto finish;
+
         if (event_next_pending(e)) {
                 e->state = SD_EVENT_PENDING;
 
@@ -2463,6 +3499,7 @@ _public_ int sd_event_dispatch(sd_event *e) {
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(e->state == SD_EVENT_PENDING, -EBUSY);
@@ -2472,14 +3509,12 @@ _public_ int sd_event_dispatch(sd_event *e) {
 
         p = event_next_pending(e);
         if (p) {
-                sd_event_ref(e);
+                _cleanup_(sd_event_unrefp) sd_event *ref = NULL;
 
+                ref = sd_event_ref(e);
                 e->state = SD_EVENT_RUNNING;
                 r = source_dispatch(p);
                 e->state = SD_EVENT_INITIAL;
-
-                sd_event_unref(e);
-
                 return r;
         }
 
@@ -2488,19 +3523,51 @@ _public_ int sd_event_dispatch(sd_event *e) {
         return 1;
 }
 
+static void event_log_delays(sd_event *e) {
+        char b[ELEMENTSOF(e->delays) * DECIMAL_STR_MAX(unsigned) + 1];
+        unsigned i;
+        int o;
+
+        for (i = o = 0; i < ELEMENTSOF(e->delays); i++) {
+                o += snprintf(&b[o], sizeof(b) - o, "%u ", e->delays[i]);
+                e->delays[i] = 0;
+        }
+        log_debug("Event loop iterations: %.*s", o, b);
+}
+
 _public_ int sd_event_run(sd_event *e, uint64_t timeout) {
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(e->state == SD_EVENT_INITIAL, -EBUSY);
 
+        if (e->profile_delays && e->last_run) {
+                usec_t this_run;
+                unsigned l;
+
+                this_run = now(CLOCK_MONOTONIC);
+
+                l = u64log2(this_run - e->last_run);
+                assert(l < sizeof(e->delays));
+                e->delays[l]++;
+
+                if (this_run - e->last_log >= 5*USEC_PER_SEC) {
+                        event_log_delays(e);
+                        e->last_log = this_run;
+                }
+        }
+
         r = sd_event_prepare(e);
         if (r == 0)
                 /* There was nothing? Then wait... */
                 r = sd_event_wait(e, timeout);
 
+        if (e->profile_delays)
+                e->last_run = now(CLOCK_MONOTONIC);
+
         if (r > 0) {
                 /* There's something now, then let's dispatch it */
                 r = sd_event_dispatch(e);
@@ -2514,30 +3581,29 @@ _public_ int sd_event_run(sd_event *e, uint64_t timeout) {
 }
 
 _public_ int sd_event_loop(sd_event *e) {
+        _cleanup_(sd_event_unrefp) sd_event *ref = NULL;
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
         assert_return(e->state == SD_EVENT_INITIAL, -EBUSY);
 
-        sd_event_ref(e);
+        ref = sd_event_ref(e);
 
         while (e->state != SD_EVENT_FINISHED) {
                 r = sd_event_run(e, (uint64_t) -1);
                 if (r < 0)
-                        goto finish;
+                        return r;
         }
 
-        r = e->exit_code;
-
-finish:
-        sd_event_unref(e);
-        return r;
+        return e->exit_code;
 }
 
 _public_ int sd_event_get_fd(sd_event *e) {
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
 
         return e->epoll_fd;
@@ -2545,6 +3611,7 @@ _public_ int sd_event_get_fd(sd_event *e) {
 
 _public_ int sd_event_get_state(sd_event *e) {
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
 
         return e->state;
@@ -2552,6 +3619,7 @@ _public_ int sd_event_get_state(sd_event *e) {
 
 _public_ int sd_event_get_exit_code(sd_event *e, int *code) {
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(code, -EINVAL);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -2564,6 +3632,7 @@ _public_ int sd_event_get_exit_code(sd_event *e, int *code) {
 
 _public_ int sd_event_exit(sd_event *e, int code) {
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(e->state != SD_EVENT_FINISHED, -ESTALE);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -2575,36 +3644,31 @@ _public_ int sd_event_exit(sd_event *e, int code) {
 
 _public_ int sd_event_now(sd_event *e, clockid_t clock, uint64_t *usec) {
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(usec, -EINVAL);
         assert_return(!event_pid_changed(e), -ECHILD);
 
-        /* If we haven't run yet, just get the actual time */
-        if (!dual_timestamp_is_set(&e->timestamp))
-                return -ENODATA;
-
-        switch (clock) {
-
-        case CLOCK_REALTIME:
-        case CLOCK_REALTIME_ALARM:
-                *usec = e->timestamp.realtime;
-                break;
+        if (!TRIPLE_TIMESTAMP_HAS_CLOCK(clock))
+                return -EOPNOTSUPP;
 
-        case CLOCK_MONOTONIC:
-                *usec = e->timestamp.monotonic;
-                break;
+        /* Generate a clean error in case CLOCK_BOOTTIME is not available. Note that don't use clock_supported() here,
+         * for a reason: there are systems where CLOCK_BOOTTIME is supported, but CLOCK_BOOTTIME_ALARM is not, but for
+         * the purpose of getting the time this doesn't matter. */
+        if (IN_SET(clock, CLOCK_BOOTTIME, CLOCK_BOOTTIME_ALARM) && !clock_boottime_supported())
+                return -EOPNOTSUPP;
 
-        case CLOCK_BOOTTIME:
-        case CLOCK_BOOTTIME_ALARM:
-                *usec = e->timestamp_boottime;
-                break;
+        if (!triple_timestamp_is_set(&e->timestamp)) {
+                /* Implicitly fall back to now() if we never ran
+                 * before and thus have no cached time. */
+                *usec = now(clock);
+                return 1;
         }
 
+        *usec = triple_timestamp_by_clock(&e->timestamp, clock);
         return 0;
 }
 
 _public_ int sd_event_default(sd_event **ret) {
-
-        static thread_local sd_event *default_event = NULL;
         sd_event *e = NULL;
         int r;
 
@@ -2630,6 +3694,7 @@ _public_ int sd_event_default(sd_event **ret) {
 
 _public_ int sd_event_get_tid(sd_event *e, pid_t *tid) {
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(tid, -EINVAL);
         assert_return(!event_pid_changed(e), -ECHILD);
 
@@ -2645,13 +3710,14 @@ _public_ int sd_event_set_watchdog(sd_event *e, int b) {
         int r;
 
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
 
         if (e->watchdog == !!b)
                 return e->watchdog;
 
         if (b) {
-                struct epoll_event ev = {};
+                struct epoll_event ev;
 
                 r = sd_watchdog_enabled(false, &e->watchdog_period);
                 if (r <= 0)
@@ -2669,8 +3735,10 @@ _public_ int sd_event_set_watchdog(sd_event *e, int b) {
                 if (r < 0)
                         goto fail;
 
-                ev.events = EPOLLIN;
-                ev.data.ptr = INT_TO_PTR(SOURCE_WATCHDOG);
+                ev = (struct epoll_event) {
+                        .events = EPOLLIN,
+                        .data.ptr = INT_TO_PTR(SOURCE_WATCHDOG),
+                };
 
                 r = epoll_ctl(e->epoll_fd, EPOLL_CTL_ADD, e->watchdog_fd, &ev);
                 if (r < 0) {
@@ -2695,7 +3763,33 @@ fail:
 
 _public_ int sd_event_get_watchdog(sd_event *e) {
         assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
         assert_return(!event_pid_changed(e), -ECHILD);
 
         return e->watchdog;
 }
+
+_public_ int sd_event_get_iteration(sd_event *e, uint64_t *ret) {
+        assert_return(e, -EINVAL);
+        assert_return(e = event_resolve(e), -ENOPKG);
+        assert_return(!event_pid_changed(e), -ECHILD);
+
+        *ret = e->iteration;
+        return 0;
+}
+
+_public_ int sd_event_source_set_destroy_callback(sd_event_source *s, sd_event_destroy_t callback) {
+        assert_return(s, -EINVAL);
+
+        s->destroy_callback = callback;
+        return 0;
+}
+
+_public_ int sd_event_source_get_destroy_callback(sd_event_source *s, sd_event_destroy_t *ret) {
+        assert_return(s, -EINVAL);
+
+        if (ret)
+                *ret = s->destroy_callback;
+
+        return !!s->destroy_callback;
+}