chiark / gitweb /
udevd: improve timeout handling
[elogind.git] / udevd.c
diff --git a/udevd.c b/udevd.c
index 91033b068844a42965d48d46db91dc2c6b2558da..b5597eab404c44b50f3258145746635b0abecbdc 100644 (file)
--- a/udevd.c
+++ b/udevd.c
@@ -38,6 +38,7 @@
 #include <sys/un.h>
 #include <sys/sysinfo.h>
 #include <sys/stat.h>
+#include <linux/netlink.h>
 
 #include "list.h"
 #include "udev_libc_wrapper.h"
 #include "logging.h"
 
 /* global variables*/
-static int udevsendsock;
+static int udevd_sock;
+static int uevent_nl_sock;
 static pid_t sid;
 
 static int pipefds[2];
-static long startup_time;
-static unsigned long long expected_seqnum = 0;
 static volatile int sigchilds_waiting;
 static volatile int run_msg_q;
 static volatile int sig_flag;
+static int init_phase = 1;
 static int run_exec_q;
+static int stop_exec_q;
 
 static LIST_HEAD(msg_list);
 static LIST_HEAD(exec_list);
@@ -67,7 +69,13 @@ static void exec_queue_manager(void);
 static void msg_queue_manager(void);
 static void user_sighandler(void);
 static void reap_sigchilds(void);
-char *udev_bin;
+
+static char *udev_bin;
+static unsigned long long expected_seqnum;
+static int event_timeout;
+static int max_childs;
+static int max_childs_running;
+
 
 #ifdef USE_LOG
 void log_message (int priority, const char *format, ...)
@@ -86,23 +94,23 @@ void log_message (int priority, const char *format, ...)
 static void msg_dump_queue(void)
 {
 #ifdef DEBUG
-       struct hotplug_msg *msg;
+       struct uevent_msg *msg;
 
        list_for_each_entry(msg, &msg_list, node)
                dbg("sequence %llu in queue", msg->seqnum);
 #endif
 }
 
-static void run_queue_delete(struct hotplug_msg *msg)
+static void run_queue_delete(struct uevent_msg *msg)
 {
        list_del(&msg->node);
        free(msg);
 }
 
 /* orders the message in the queue by sequence number */
-static void msg_queue_insert(struct hotplug_msg *msg)
+static void msg_queue_insert(struct uevent_msg *msg)
 {
-       struct hotplug_msg *loop_msg;
+       struct uevent_msg *loop_msg;
        struct sysinfo info;
 
        if (msg->seqnum == 0) {
@@ -112,6 +120,20 @@ static void msg_queue_insert(struct hotplug_msg *msg)
                return;
        }
 
+       /* store timestamp of queuing */
+       sysinfo(&info);
+       msg->queue_time = info.uptime;
+
+       /* with the first event we provide a phase of shorter timeout */
+       if (init_phase) {
+               static long init_time;
+
+               if (init_time == 0)
+                       init_time = info.uptime;
+               if (info.uptime - init_time >= UDEVD_INIT_TIME)
+                       init_phase = 0;
+       }
+
        /* don't delay messages with timeout set */
        if (msg->timeout) {
                dbg("move seq %llu with timeout %u to exec queue", msg->seqnum, msg->timeout);
@@ -126,17 +148,13 @@ static void msg_queue_insert(struct hotplug_msg *msg)
                        break;
 
                if (loop_msg->seqnum == msg->seqnum) {
-                       info("ignoring duplicate message seq %llu", msg->seqnum);
+                       dbg("ignoring duplicate message seq %llu", msg->seqnum);
+                       free(msg);
                        return;
                }
        }
-
-       /* store timestamp of queuing */
-       sysinfo(&info);
-       msg->queue_time = info.uptime;
-
        list_add(&msg->node, &loop_msg->node);
-       dbg("queued message seq %llu", msg->seqnum);
+       info("seq %llu queued, devpath '%s'", msg->seqnum, msg->devpath);
 
        /* run msg queue manager */
        run_msg_q = 1;
@@ -145,16 +163,19 @@ static void msg_queue_insert(struct hotplug_msg *msg)
 }
 
 /* forks event and removes event from run queue when finished */
-static void execute_udev(struct hotplug_msg *msg)
+static void execute_udev(struct uevent_msg *msg)
 {
        char *const argv[] = { "udev", msg->subsystem, NULL };
        pid_t pid;
+       struct sysinfo info;
 
        pid = fork();
        switch (pid) {
        case 0:
                /* child */
-               close(udevsendsock);
+               if (uevent_nl_sock != -1)
+                       close(uevent_nl_sock);
+               close(udevd_sock);
                logging_close();
 
                setpriority(PRIO_PROCESS, 0, UDEV_PRIORITY);
@@ -168,7 +189,9 @@ static void execute_udev(struct hotplug_msg *msg)
                break;
        default:
                /* get SIGCHLD in main loop */
-               dbg("==> exec seq %llu [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
+               sysinfo(&info);
+               info("seq %llu forked, pid %d, %ld seconds old",
+                    msg->seqnum, pid, info.uptime - msg->queue_time);
                msg->pid = pid;
        }
 }
@@ -293,73 +316,81 @@ static int compare_devpath(const char *running, const char *waiting)
 }
 
 /* returns still running task for the same device, its parent or its physical device */
-static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
+static int running_with_devpath(struct uevent_msg *msg, int limit)
 {
-       struct hotplug_msg *loop_msg;
+       struct uevent_msg *loop_msg;
+       int childs_count = 0;
 
        if (msg->devpath == NULL)
-               return NULL;
+               return 0;
 
        /* skip any events with a timeout set */
-       if (msg->timeout)
-               return NULL;
+       if (msg->timeout != 0)
+               return 0;
 
        list_for_each_entry(loop_msg, &running_list, node) {
+               if (limit && childs_count++ > limit) {
+                       dbg("%llu, maximum number (%i) of child reached", msg->seqnum, childs_count);
+                       return 1;
+               }
                if (loop_msg->devpath == NULL)
                        continue;
 
                /* return running parent/child device event */
-               if (compare_devpath(loop_msg->devpath, msg->devpath) != 0)
-                       return loop_msg;
+               if (compare_devpath(loop_msg->devpath, msg->devpath) != 0) {
+                       dbg("%llu, child device event still running %llu (%s)",
+                           msg->seqnum, loop_msg->seqnum, loop_msg->devpath);
+                       return 2;
+               }
 
                /* return running physical device event */
                if (msg->physdevpath && msg->action && strcmp(msg->action, "add") == 0)
-                       if (compare_devpath(loop_msg->devpath, msg->physdevpath) != 0)
-                               return loop_msg;
+                       if (compare_devpath(loop_msg->devpath, msg->physdevpath) != 0) {
+                               dbg("%llu, physical device event still running %llu (%s)",
+                                   msg->seqnum, loop_msg->seqnum, loop_msg->devpath);
+                               return 3;
+                       }
        }
 
-       return NULL;
+       return 0;
 }
 
 /* exec queue management routine executes the events and serializes events in the same sequence */
 static void exec_queue_manager(void)
 {
-       struct hotplug_msg *loop_msg;
-       struct hotplug_msg *tmp_msg;
-       struct hotplug_msg *msg;
+       struct uevent_msg *loop_msg;
+       struct uevent_msg *tmp_msg;
        int running;
 
        running = running_processes();
        dbg("%d processes runnning on system", running);
        if (running < 0)
-               running = THROTTLE_MAX_RUNNING_CHILDS;
+               running = max_childs_running;
 
        list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, node) {
                /* check running processes in our session and possibly throttle */
-               if (running >= THROTTLE_MAX_RUNNING_CHILDS) {
-                       running = running_processes_in_session(sid, THROTTLE_MAX_RUNNING_CHILDS+10);
-                       dbg("%d processes running in session", running);
-                       if (running >= THROTTLE_MAX_RUNNING_CHILDS) {
-                               dbg("delay seq %llu, cause too many processes already running", loop_msg->seqnum);
+               if (running >= max_childs_running) {
+                       running = running_processes_in_session(sid, max_childs_running+10);
+                       dbg("at least %d processes running in session", running);
+                       if (running >= max_childs_running) {
+                               dbg("delay seq %llu, cause too many processes already running",
+                                   loop_msg->seqnum);
                                return;
                        }
                }
 
-               msg = running_with_devpath(loop_msg);
-               if (!msg) {
+               if (running_with_devpath(loop_msg, max_childs) == 0) {
                        /* move event to run list */
                        list_move_tail(&loop_msg->node, &running_list);
                        execute_udev(loop_msg);
                        running++;
                        dbg("moved seq %llu to running list", loop_msg->seqnum);
-               } else {
-                       dbg("delay seq %llu (%s), cause seq %llu (%s) is still running",
-                           loop_msg->seqnum, loop_msg->devpath, msg->seqnum, msg->devpath);
-               }
+               } else
+                       dbg("delay seq %llu (%s)", loop_msg->seqnum, loop_msg->devpath);
        }
 }
 
-static void msg_move_exec(struct hotplug_msg *msg)
+static void msg_move_exec(struct uevent_msg *msg)
 {
        list_move_tail(&msg->node, &exec_list);
        run_exec_q = 1;
@@ -371,15 +402,15 @@ static void msg_move_exec(struct hotplug_msg *msg)
 /* msg queue management routine handles the timeouts and dispatches the events */
 static void msg_queue_manager(void)
 {
-       struct hotplug_msg *loop_msg;
-       struct hotplug_msg *tmp_msg;
+       struct uevent_msg *loop_msg;
+       struct uevent_msg *tmp_msg;
        struct sysinfo info;
        long msg_age = 0;
-       static int timeout = EVENT_INIT_TIMEOUT_SEC;
-       static int init = 1;
+       int timeout = event_timeout;
 
        dbg("msg queue manager, next expected is %llu", expected_seqnum);
 recheck:
+       sysinfo(&info);
        list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, node) {
                /* move event with expected sequence to the exec list */
                if (loop_msg->seqnum == expected_seqnum) {
@@ -387,15 +418,13 @@ recheck:
                        continue;
                }
 
-               /* see if we are in the initialization phase and wait for the very first events */
-               if (init && (info.uptime - startup_time >= INIT_TIME_SEC)) {
-                       init = 0;
-                       timeout = EVENT_TIMEOUT_SEC;
-                       dbg("initialization phase passed, set timeout to %i seconds", EVENT_TIMEOUT_SEC);
+               /* limit timeout during initialization phase */
+               if (init_phase) {
+                       timeout = UDEVD_INIT_EVENT_TIMEOUT;
+                       dbg("initialization phase, limit timeout to %i seconds", UDEVD_INIT_EVENT_TIMEOUT);
                }
 
                /* move event with expired timeout to the exec list */
-               sysinfo(&info);
                msg_age = info.uptime - loop_msg->queue_time;
                dbg("seq %llu is %li seconds old", loop_msg->seqnum, msg_age);
                if (msg_age >= timeout) {
@@ -416,13 +445,60 @@ recheck:
        }
 }
 
-/* receive the udevsend message and do some sanity checks */
-static struct hotplug_msg *get_udevsend_msg(void)
+static struct uevent_msg *get_msg_from_envbuf(const char *buf, int buf_size)
 {
-       static struct udevsend_msg usend_msg;
-       struct hotplug_msg *msg;
        int bufpos;
        int i;
+       struct uevent_msg *msg;
+
+       msg = malloc(sizeof(struct uevent_msg) + buf_size);
+       if (msg == NULL)
+               return NULL;
+       memset(msg, 0x00, sizeof(struct uevent_msg) + buf_size);
+
+       /* copy environment buffer and reconstruct envp */
+       memcpy(msg->envbuf, buf, buf_size);
+       bufpos = 0;
+       for (i = 0; (bufpos < buf_size) && (i < UEVENT_NUM_ENVP-2); i++) {
+               int keylen;
+               char *key;
+
+               key = &msg->envbuf[bufpos];
+               keylen = strlen(key);
+               msg->envp[i] = key;
+               bufpos += keylen + 1;
+               dbg("add '%s' to msg.envp[%i]", msg->envp[i], i);
+
+               /* remember some keys for further processing */
+               if (strncmp(key, "ACTION=", 7) == 0)
+                       msg->action = &key[7];
+
+               if (strncmp(key, "DEVPATH=", 8) == 0)
+                       msg->devpath = &key[8];
+
+               if (strncmp(key, "SUBSYSTEM=", 10) == 0)
+                       msg->subsystem = &key[10];
+
+               if (strncmp(key, "SEQNUM=", 7) == 0)
+                       msg->seqnum = strtoull(&key[7], NULL, 10);
+
+               if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
+                       msg->physdevpath = &key[12];
+
+               if (strncmp(key, "TIMEOUT=", 8) == 0)
+                       msg->timeout = strtoull(&key[8], NULL, 10);
+       }
+       msg->envp[i++] = "UDEVD_EVENT=1";
+       msg->envp[i] = NULL;
+
+       return msg;
+}
+
+/* receive the udevd message from userspace */
+static struct uevent_msg *get_udevd_msg(void)
+{
+       static struct udevd_msg usend_msg;
+       struct uevent_msg *msg;
        ssize_t size;
        struct msghdr smsg;
        struct cmsghdr *cmsg;
@@ -431,9 +507,9 @@ static struct hotplug_msg *get_udevsend_msg(void)
        char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
        int envbuf_size;
 
-       memset(&usend_msg, 0x00, sizeof(struct udevsend_msg));
+       memset(&usend_msg, 0x00, sizeof(struct udevd_msg));
        iov.iov_base = &usend_msg;
-       iov.iov_len = sizeof(struct udevsend_msg);
+       iov.iov_len = sizeof(struct udevd_msg);
 
        memset(&smsg, 0x00, sizeof(struct msghdr));
        smsg.msg_iov = &iov;
@@ -441,10 +517,10 @@ static struct hotplug_msg *get_udevsend_msg(void)
        smsg.msg_control = cred_msg;
        smsg.msg_controllen = sizeof(cred_msg);
 
-       size = recvmsg(udevsendsock, &smsg, 0);
+       size = recvmsg(udevd_sock, &smsg, 0);
        if (size <  0) {
                if (errno != EINTR)
-                       dbg("unable to receive udevsend message");
+                       dbg("unable to receive udevd message");
                return NULL;
        }
        cmsg = CMSG_FIRSTHDR(&smsg);
@@ -465,48 +541,77 @@ static struct hotplug_msg *get_udevsend_msg(void)
                return NULL;
        }
 
-       envbuf_size = size - offsetof(struct udevsend_msg, envbuf);
-       dbg("envbuf_size=%i", envbuf_size);
-       msg = malloc(sizeof(struct hotplug_msg) + envbuf_size);
-       if (msg == NULL)
-               return NULL;
-
-       memset(msg, 0x00, sizeof(struct hotplug_msg) + envbuf_size);
-
-       /* copy environment buffer and reconstruct envp */
-       memcpy(msg->envbuf, usend_msg.envbuf, envbuf_size);
-       bufpos = 0;
-       for (i = 0; (bufpos < envbuf_size) && (i < HOTPLUG_NUM_ENVP-2); i++) {
-               int keylen;
-               char *key;
+switch (usend_msg.type) {
+       case UDEVD_UEVENT:
+               dbg("udevd message (UEVENT) received");
+               envbuf_size = size - offsetof(struct udevd_msg, envbuf);
+               dbg("envbuf_size=%i", envbuf_size);
+               msg = get_msg_from_envbuf(usend_msg.envbuf, envbuf_size);
+               if (msg == NULL)
+                       return NULL;
+               return msg;
+       case UDEVD_STOP_EXEC_QUEUE:
+               dbg("udevd message (STOP_EXEC_QUEUE) received");
+               stop_exec_q = 1;
+               break;
+       case UDEVD_START_EXEC_QUEUE:
+               dbg("udevd message (START_EXEC_QUEUE) received");
+               stop_exec_q = 0;
+               exec_queue_manager();
+               break;
+       default:
+               dbg("unknown message type");
+       }
+       return NULL;
+}
 
-               key = &msg->envbuf[bufpos];
-               keylen = strlen(key);
-               msg->envp[i] = key;
-               bufpos += keylen + 1;
-               dbg("add '%s' to msg.envp[%i]", msg->envp[i], i);
+/* receive the kernel user event message and do some sanity checks */
+static struct uevent_msg *get_uevent_msg(void)
+{
+       struct uevent_msg *msg;
+       int bufpos;
+       ssize_t size;
+       static char buffer[UEVENT_BUFFER_SIZE + 512];
+       char *pos;
 
-               /* remember some keys for further processing */
-               if (strncmp(key, "ACTION=", 7) == 0)
-                       msg->action = &key[7];
+       size = recv(uevent_nl_sock, &buffer, sizeof(buffer), 0);
+       if (size <  0) {
+               if (errno != EINTR)
+                       dbg("unable to receive udevd message");
+               return NULL;
+       }
 
-               if (strncmp(key, "DEVPATH=", 8) == 0)
-                       msg->devpath = &key[8];
+       if ((size_t)size > sizeof(buffer)-1)
+               size = sizeof(buffer)-1;
+       buffer[size] = '\0';
+       dbg("uevent_size=%i", size);
 
-               if (strncmp(key, "SUBSYSTEM=", 10) == 0)
-                       msg->subsystem = &key[10];
+       /* start of event payload */
+       bufpos = strlen(buffer)+1;
+       msg = get_msg_from_envbuf(&buffer[bufpos], size-bufpos);
+       if (msg == NULL)
+               return NULL;
 
-               if (strncmp(key, "SEQNUM=", 7) == 0)
-                       msg->seqnum = strtoull(&key[7], NULL, 10);
+       /* validate message */
+       pos = strchr(buffer, '@');
+       if (pos == NULL) {
+               dbg("invalid uevent '%s'", buffer);
+               free(msg);
+               return NULL;
+       }
+       pos[0] = '\0';
 
-               if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
-                       msg->physdevpath = &key[12];
+       if (msg->action == NULL) {
+               dbg("no ACTION in payload found, skip event '%s'", buffer);
+               free(msg);
+               return NULL;
+       }
 
-               if (strncmp(key, "TIMEOUT=", 8) == 0)
-                       msg->timeout = strtoull(&key[8], NULL, 10);
+       if (strcmp(msg->action, buffer) != 0) {
+               dbg("ACTION in payload does not match uevent, skip event '%s'", buffer);
+               free(msg);
+               return NULL;
        }
-       msg->envp[i++] = "UDEVD_EVENT=1";
-       msg->envp[i] = NULL;
 
        return msg;
 }
@@ -546,11 +651,13 @@ do_write:
 static void udev_done(int pid)
 {
        /* find msg associated with pid and delete it */
-       struct hotplug_msg *msg;
+       struct uevent_msg *msg;
+       struct sysinfo info;
 
        list_for_each_entry(msg, &running_list, node) {
                if (msg->pid == pid) {
-                       dbg("<== exec seq %llu came back", msg->seqnum);
+                       sysinfo(&info);
+                       info("seq %llu exit, %ld sec old", msg->seqnum, info.uptime - msg->queue_time);
                        run_queue_delete(msg);
 
                        /* we want to run the exec queue manager since there may
@@ -589,7 +696,7 @@ static void user_sighandler(void)
        }
 }
 
-static int init_udevsend_socket(void)
+static int init_udevd_socket(void)
 {
        struct sockaddr_un saddr;
        socklen_t addrlen;
@@ -602,35 +709,63 @@ static int init_udevsend_socket(void)
        strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
        addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 
-       udevsendsock = socket(AF_LOCAL, SOCK_DGRAM, 0);
-       if (udevsendsock == -1) {
+       udevd_sock = socket(AF_LOCAL, SOCK_DGRAM, 0);
+       if (udevd_sock == -1) {
                err("error getting socket, %s", strerror(errno));
                return -1;
        }
 
        /* the bind takes care of ensuring only one copy running */
-       retval = bind(udevsendsock, (struct sockaddr *) &saddr, addrlen);
+       retval = bind(udevd_sock, (struct sockaddr *) &saddr, addrlen);
        if (retval < 0) {
                err("bind failed, %s", strerror(errno));
-               close(udevsendsock);
+               close(udevd_sock);
                return -1;
        }
 
        /* enable receiving of the sender credentials */
-       setsockopt(udevsendsock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));
+       setsockopt(udevd_sock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));
+
+       return 0;
+}
+
+static int init_uevent_nl_sock(void)
+{
+       struct sockaddr_nl snl;
+       int retval;
+
+       memset(&snl, 0x00, sizeof(struct sockaddr_nl));
+       snl.nl_family = AF_NETLINK;
+       snl.nl_pid = getpid();
+       snl.nl_groups = 0xffffffff;
+
+       uevent_nl_sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
+       if (uevent_nl_sock == -1) {
+               dbg("error getting socket, %s", strerror(errno));
+               return -1;
+       }
+
+       retval = bind(uevent_nl_sock, (struct sockaddr *) &snl,
+                     sizeof(struct sockaddr_nl));
+       if (retval < 0) {
+               dbg("bind failed, %s", strerror(errno));
+               close(uevent_nl_sock);
+               uevent_nl_sock = -1;
+               return -1;
+       }
 
        return 0;
 }
 
 int main(int argc, char *argv[], char *envp[])
 {
-       struct sysinfo info;
        int maxsockplus;
        int retval;
        int fd;
        struct sigaction act;
        fd_set readfds;
-       const char *udevd_expected_seqnum;
+       const char *value;
+       int uevent_nl_active = 0;
 
        logging_init("udevd");
        udev_init_config();
@@ -663,7 +798,6 @@ int main(int argc, char *argv[], char *envp[])
        sid = setsid();
        dbg("our session is %d", sid);
 
-       /* make sure we don't lock any path */
        chdir("/");
        umask(umask(077) | 022);
 
@@ -716,39 +850,65 @@ int main(int argc, char *argv[], char *envp[])
        sigaction(SIGALRM, &act, NULL);
        sigaction(SIGCHLD, &act, NULL);
 
-       if (init_udevsend_socket() < 0) {
+       if (init_uevent_nl_sock() < 0) {
+               dbg("uevent socket not available");
+       }
+
+       if (init_udevd_socket() < 0) {
                if (errno == EADDRINUSE)
                        dbg("another udevd running, exit");
                else
-                       dbg("error initialising udevsend socket: %s", strerror(errno));
+                       dbg("error initialising udevd socket: %s", strerror(errno));
 
                goto exit;
        }
 
-       /* possible override of udev binary, used for testing */
+       /* override of forked udev binary, used for testing */
        udev_bin = getenv("UDEV_BIN");
        if (udev_bin != NULL)
                info("udev binary is set to '%s'", udev_bin);
        else
                udev_bin = UDEV_BIN;
 
-       /* possible init of expected_seqnum value */
-       udevd_expected_seqnum = getenv("UDEVD_EXPECTED_SEQNUM");
-       if (udevd_expected_seqnum != NULL) {
-               expected_seqnum = strtoull(udevd_expected_seqnum, NULL, 10);
+       /* init of expected_seqnum value */
+       value = getenv("UDEVD_EXPECTED_SEQNUM");
+       if (value) {
+               expected_seqnum = strtoull(value, NULL, 10);
                info("initialize expected_seqnum to %llu", expected_seqnum);
        }
 
-       /* get current time to provide shorter timeout on startup */
-       sysinfo(&info);
-       startup_time = info.uptime;
+       /* timeout to wait for missing events */
+       value = getenv("UDEVD_EVENT_TIMEOUT");
+       if (value)
+               event_timeout = strtoul(value, NULL, 10);
+       else
+               event_timeout = UDEVD_EVENT_TIMEOUT;
+       info("initialize event_timeout to %u", event_timeout);
+
+       /* maximum limit of forked childs */
+       value = getenv("UDEVD_MAX_CHILDS");
+       if (value)
+               max_childs = strtoul(value, NULL, 10);
+       else
+               max_childs = UDEVD_MAX_CHILDS;
+       info("initialize max_childs to %u", max_childs);
+
+       /* start to throttle forking if maximum number of _running_ childs is reached */
+       value = getenv("UDEVD_MAX_CHILDS_RUNNING");
+       if (value)
+               max_childs_running = strtoull(value, NULL, 10);
+       else
+               max_childs_running = UDEVD_MAX_CHILDS_RUNNING;
+       info("initialize max_childs_running to %u", max_childs_running);
 
        FD_ZERO(&readfds);
-       FD_SET(udevsendsock, &readfds);
+       FD_SET(udevd_sock, &readfds);
+       if (uevent_nl_sock != -1)
+               FD_SET(uevent_nl_sock, &readfds);
        FD_SET(pipefds[0], &readfds);
-       maxsockplus = udevsendsock+1;
+       maxsockplus = udevd_sock+1;
        while (1) {
-               struct hotplug_msg *msg;
+               struct uevent_msg *msg;
 
                fd_set workreadfds = readfds;
                retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
@@ -759,10 +919,29 @@ int main(int argc, char *argv[], char *envp[])
                        continue;
                }
 
-               if (FD_ISSET(udevsendsock, &workreadfds)) {
-                       msg = get_udevsend_msg();
-                       if (msg)
+               if (FD_ISSET(udevd_sock, &workreadfds)) {
+                       msg = get_udevd_msg();
+                       if (msg) {
+                               /* discard kernel messages if netlink is active */
+                               if (uevent_nl_active && msg->seqnum != 0) {
+                                       dbg("skip uevent_helper message, netlink is active");
+                                       free(msg);
+                                       continue;
+                               }
                                msg_queue_insert(msg);
+                       }
+               }
+
+               if (FD_ISSET(uevent_nl_sock, &workreadfds)) {
+                       msg = get_uevent_msg();
+                       if (msg) {
+                               msg_queue_insert(msg);
+                               /* disable kernel uevent_helper with first netlink message */
+                               if (!uevent_nl_active) {
+                                       info("uevent_nl message received, disable uevent_helper messages");
+                                       uevent_nl_active = 1;
+                               }
+                       }
                }
 
                if (FD_ISSET(pipefds[0], &workreadfds))
@@ -786,7 +965,8 @@ int main(int argc, char *argv[], char *envp[])
                        }
 
                        run_exec_q = 0;
-                       exec_queue_manager();
+                       if (!stop_exec_q)
+                               exec_queue_manager();
                }
        }