X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?p=elogind.git;a=blobdiff_plain;f=udevd.c;h=fa14c56073cfd042c7912861cc08d7bdd9c3670e;hp=331b7e4b84aa9d0229f709268dcbe58248e88701;hb=47e353f9b9c1a95d4e7cdf0e9be3d746585851f1;hpb=95a6f4c8acafe7031087667aa556a50a6a091c93

diff --git a/udevd.c b/udevd.c
index 331b7e4b8..fa14c5607 100644
--- a/udevd.c
+++ b/udevd.c
@@ -1,7 +1,8 @@
 /*
  * udevd.c - hotplug event serializer
  *
- * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
+ * Copyright (C) 2004-2005 Kay Sievers <kay.sievers@vrfy.org>
+ * Copyright (C) 2004 Chris Friesen <chris_friesen@sympatico.ca>
  *
  *
  *	This program is free software; you can redistribute it and/or modify it
@@ -19,401 +20,995 @@
  *
  */
 
-#include <pthread.h>
 #include <stddef.h>
-#include <sys/types.h>
-#include <sys/wait.h>
 #include <signal.h>
 #include <unistd.h>
 #include <errno.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <time.h>
+#include <ctype.h>
+#include <dirent.h>
 #include <fcntl.h>
+#include <sys/select.h>
+#include <sys/wait.h>
+#include <sys/time.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <sys/sysinfo.h>
+#include <sys/stat.h>
+#include <linux/types.h>
+#include <linux/netlink.h>
 
 #include "list.h"
+#include "udev_libc_wrapper.h"
 #include "udev.h"
 #include "udev_version.h"
+#include "udev_utils.h"
 #include "udevd.h"
 #include "logging.h"
 
+/* global variables*/
+static int udevd_sock;
+static int uevent_netlink_sock;
+static pid_t sid;
+
+static int pipefds[2];
+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);
+static LIST_HEAD(running_list);
+
+static void exec_queue_manager(void);
+static void msg_queue_manager(void);
+static void user_sighandler(void);
+static void reap_sigchilds(void);
+
+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, ...)
+{
+	va_list args;
 
-unsigned char logname[42];
-static pthread_mutex_t  msg_lock;
-static pthread_mutex_t  msg_active_lock;
-static pthread_cond_t msg_active;
-static pthread_mutex_t  exec_lock;
-static pthread_mutex_t  exec_active_lock;
-static pthread_cond_t exec_active;
-static pthread_mutex_t  running_lock;
-static pthread_attr_t thr_attr;
-static int expected_seqnum = 0;
-
-LIST_HEAD(msg_list);
-LIST_HEAD(exec_list);
-LIST_HEAD(running_list);
+	if (priority > udev_log_priority)
+		return;
 
+	va_start(args, format);
+	vsyslog(priority, format, args);
+	va_end(args);
+}
+#endif
 
 static void msg_dump_queue(void)
 {
-	struct hotplug_msg *msg;
+#ifdef DEBUG
+	struct uevent_msg *msg;
 
-	list_for_each_entry(msg, &msg_list, list)
-		dbg("sequence %d in queue", msg->seqnum);
+	list_for_each_entry(msg, &msg_list, node)
+		dbg("sequence %llu in queue", msg->seqnum);
+#endif
 }
 
-static void msg_dump(struct hotplug_msg *msg)
+static void msg_queue_delete(struct uevent_msg *msg)
 {
-	dbg("sequence %d, '%s', '%s', '%s'",
-	    msg->seqnum, msg->action, msg->devpath, msg->subsystem);
+	list_del(&msg->node);
+	free(msg);
 }
 
-static struct hotplug_msg *msg_create(void)
+/* orders the message in the queue by sequence number */
+static void msg_queue_insert(struct uevent_msg *msg)
 {
-	struct hotplug_msg *new_msg;
-
-	new_msg = malloc(sizeof(struct hotplug_msg));
-	if (new_msg == NULL) {
-		dbg("error malloc");
-		return NULL;
+	struct uevent_msg *loop_msg;
+	struct sysinfo info;
+
+	if (msg->seqnum == 0) {
+		dbg("no SEQNUM, move straight to the exec queue");
+		list_add(&msg->node, &exec_list);
+		run_exec_q = 1;
+		return;
 	}
-	return new_msg;
-}
 
-static void msg_delete(struct hotplug_msg *msg)
-{
-	if (msg != NULL)
-		free(msg);
-}
+	/* store timestamp of queuing */
+	sysinfo(&info);
+	msg->queue_time = info.uptime;
 
-/* orders the message in the queue by sequence number */
-static void msg_queue_insert(struct hotplug_msg *msg)
-{
-	struct hotplug_msg *loop_msg;
+	/* 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;
+	}
 
-	/* sort message by sequence number into list*/
-	list_for_each_entry(loop_msg, &msg_list, list)
-		if (loop_msg->seqnum > msg->seqnum)
+	/* don't delay messages with timeout set */
+	if (msg->timeout) {
+		dbg("move seq %llu with timeout %u to exec queue", msg->seqnum, msg->timeout);
+		list_add(&msg->node, &exec_list);
+		run_exec_q = 1;
+		return;
+	}
+
+	/* sort message by sequence number into list */
+	list_for_each_entry_reverse(loop_msg, &msg_list, node) {
+		if (loop_msg->seqnum < msg->seqnum)
 			break;
-	list_add_tail(&msg->list, &loop_msg->list);
-	dbg("queued message seq %d", msg->seqnum);
 
-	/* store timestamp of queuing */
-	msg->queue_time = time(NULL);
+		if (loop_msg->seqnum == msg->seqnum) {
+			dbg("ignoring duplicate message seq %llu", msg->seqnum);
+			free(msg);
+			return;
+		}
+	}
+	list_add(&msg->node, &loop_msg->node);
+	info("seq %llu queued, devpath '%s'", msg->seqnum, msg->devpath);
 
-	/* signal queue activity to manager */
-	pthread_mutex_lock(&msg_active_lock);
-	pthread_cond_signal(&msg_active);
-	pthread_mutex_unlock(&msg_active_lock);
+	/* run msg queue manager */
+	run_msg_q = 1;
 
-	return ;
+	return;
 }
 
 /* forks event and removes event from run queue when finished */
-static void *run_threads(void * parm)
+static void udev_event_fork(struct uevent_msg *msg)
 {
+	char *const argv[] = { "udev", msg->subsystem, NULL };
 	pid_t pid;
-	struct hotplug_msg *msg;
-
-	msg = parm;
-	setenv("ACTION", msg->action, 1);
-	setenv("DEVPATH", msg->devpath, 1);
+	struct sysinfo info;
 
 	pid = fork();
 	switch (pid) {
 	case 0:
 		/* child */
-		execl(UDEV_BIN, "udev", msg->subsystem, NULL);
-		dbg("exec of child failed");
-		exit(1);
-		break;
+		if (uevent_netlink_sock != -1)
+			close(uevent_netlink_sock);
+		close(udevd_sock);
+		logging_close();
+		setpriority(PRIO_PROCESS, 0, UDEV_PRIORITY);
+		execve(udev_bin, argv, msg->envp);
+		err("exec of child failed");
+		_exit(1);
 	case -1:
-		dbg("fork of child failed");
-		goto exit;
+		err("fork of child failed");
+		msg_queue_delete(msg);
+		break;
 	default:
-		/* wait for exit of child */
-		dbg("==> exec seq %d [%d] working at '%s'",
-		    msg->seqnum, pid, msg->devpath);
-		wait(NULL);
-		dbg("<== exec seq %d came back", msg->seqnum);
+		/* get SIGCHLD in main loop */
+		sysinfo(&info);
+		info("seq %llu forked, pid %d, %ld seconds old",
+		     msg->seqnum, pid, info.uptime - msg->queue_time);
+		msg->pid = pid;
 	}
+}
 
-exit:
-	/* remove event from run list */
-	pthread_mutex_lock(&running_lock);
-	list_del_init(&msg->list);
-	pthread_mutex_unlock(&running_lock);
+static int running_processes(void)
+{
+	int f;
+	static char buf[4096];
+	int len;
+	int running;
+	const char *pos;
+
+	f = open("/proc/stat", O_RDONLY);
+	if (f == -1)
+		return -1;
+
+	len = read(f, buf, sizeof(buf));
+	close(f);
+
+	if (len <= 0)
+		return -1;
+	else
+		buf[len] = '\0';
 
-	msg_delete(msg);
+	pos = strstr(buf, "procs_running ");
+	if (pos == NULL)
+		return -1;
 
-	/* signal queue activity to exec manager */
-	pthread_mutex_lock(&exec_active_lock);
-	pthread_cond_signal(&exec_active);
-	pthread_mutex_unlock(&exec_active_lock);
+	if (sscanf(pos, "procs_running %u", &running) != 1)
+		return -1;
 
-	pthread_exit(0);
+	return running;
 }
 
-/* returns already running task with devpath */
-static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
+/* return the number of process es in our session, count only until limit */
+static int running_processes_in_session(pid_t session, int limit)
 {
-	struct hotplug_msg *loop_msg;
-	struct hotplug_msg *tmp_msg;
+	DIR *dir;
+	struct dirent *dent;
+	int running = 0;
 
-	list_for_each_entry_safe(loop_msg, tmp_msg, &running_list, list)
-		if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
-			return loop_msg;
-	return NULL;
+	dir = opendir("/proc");
+	if (!dir)
+		return -1;
+
+	/* read process info from /proc */
+	for (dent = readdir(dir); dent != NULL; dent = readdir(dir)) {
+		int f;
+		char procdir[64];
+		char line[256];
+		const char *pos;
+		char state;
+		pid_t ppid, pgrp, sess;
+		int len;
+
+		if (!isdigit(dent->d_name[0]))
+			continue;
+
+		snprintf(procdir, sizeof(procdir), "/proc/%s/stat", dent->d_name);
+		procdir[sizeof(procdir)-1] = '\0';
+
+		f = open(procdir, O_RDONLY);
+		if (f == -1)
+			continue;
+
+		len = read(f, line, sizeof(line));
+		close(f);
+
+		if (len <= 0)
+			continue;
+		else
+			line[len] = '\0';
+
+		/* skip ugly program name */
+		pos = strrchr(line, ')') + 2;
+		if (pos == NULL)
+			continue;
+
+		if (sscanf(pos, "%c %d %d %d ", &state, &ppid, &pgrp, &sess) != 4)
+			continue;
+
+		/* count only processes in our session */
+		if (sess != session)
+			continue;
+
+		/* count only running, no sleeping processes */
+		if (state != 'R')
+			continue;
+
+		running++;
+		if (limit > 0 && running >= limit)
+			break;
+	}
+	closedir(dir);
+
+	return running;
 }
 
-/* queue management executes the events and delays events for the same devpath */
-static void *exec_queue_manager(void * parm)
+static int compare_devpath(const char *running, const char *waiting)
 {
-	struct hotplug_msg *loop_msg;
-	struct hotplug_msg *tmp_msg;
-	struct hotplug_msg *msg;
-	pthread_t run_tid;
+	int i;
 
-	while (1) {
-		pthread_mutex_lock(&exec_lock);
-		list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
-			msg = running_with_devpath(loop_msg);
-			if (msg == NULL) {
-				/* move event to run list */
-				pthread_mutex_lock(&running_lock);
-				list_move_tail(&loop_msg->list, &running_list);
-				pthread_mutex_unlock(&running_lock);
-
-				pthread_create(&run_tid, &thr_attr, run_threads, (void *) loop_msg);
-
-				dbg("moved seq %d to running list", loop_msg->seqnum);
-			} else {
-				dbg("delay seq %d, cause seq %d already working on '%s'",
-				    loop_msg->seqnum, msg->seqnum, msg->devpath);
+	for (i = 0; i < PATH_SIZE; i++) {
+		/* identical device event found */
+		if (running[i] == '\0' && waiting[i] == '\0')
+			return 1;
+
+		/* parent device event found */
+		if (running[i] == '\0' && waiting[i] == '/')
+			return 2;
+
+		/* child device event found */
+		if (running[i] == '/' && waiting[i] == '\0')
+			return 3;
+
+		/* no matching event */
+		if (running[i] != waiting[i])
+			break;
+	}
+
+	return 0;
+}
+
+/* returns still running task for the same device, its parent or its physical device */
+static int running_with_devpath(struct uevent_msg *msg, int limit)
+{
+	struct uevent_msg *loop_msg;
+	int childs_count = 0;
+
+	if (msg->devpath == NULL)
+		return 0;
+
+	/* skip any events with a timeout set */
+	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) {
+			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) {
+				dbg("%llu, physical device event still running %llu (%s)",
+				    msg->seqnum, loop_msg->seqnum, loop_msg->devpath);
+				return 3;
+			}
+	}
+
+	return 0;
+}
+
+/* exec queue management routine executes the events and serializes events in the same sequence */
+static void exec_queue_manager(void)
+{
+	struct uevent_msg *loop_msg;
+	struct uevent_msg *tmp_msg;
+	int running;
+
+	if (list_empty(&exec_list))
+		return;
+
+	running = running_processes();
+	dbg("%d processes runnning on system", running);
+	if (running < 0)
+		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 >= 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;
 			}
 		}
-		pthread_mutex_unlock(&exec_lock);
 
-		/* wait for activation, new events or childs coming back */
-		pthread_mutex_lock(&exec_active_lock);
-		pthread_cond_wait(&exec_active, &exec_active_lock);
-		pthread_mutex_unlock(&exec_active_lock);
+		if (running_with_devpath(loop_msg, max_childs) == 0) {
+			/* move event to run list */
+			list_move_tail(&loop_msg->node, &running_list);
+			udev_event_fork(loop_msg);
+			running++;
+			dbg("moved seq %llu to running list", loop_msg->seqnum);
+		} else
+			dbg("delay seq %llu (%s)", loop_msg->seqnum, loop_msg->devpath);
 	}
 }
 
-/* move message from incoming to exec queue */
-static void msg_move_exec(struct list_head *head)
+static void msg_move_exec(struct uevent_msg *msg)
 {
-	list_move_tail(head, &exec_list);
-	/* signal queue activity to manager */
-	pthread_mutex_lock(&exec_active_lock);
-	pthread_cond_signal(&exec_active);
-	pthread_mutex_unlock(&exec_active_lock);
+	list_move_tail(&msg->node, &exec_list);
+	run_exec_q = 1;
+	expected_seqnum = msg->seqnum+1;
+	dbg("moved seq %llu to exec, next expected is %llu",
+		msg->seqnum, expected_seqnum);
 }
 
-/* queue management thread handles the timeouts and dispatches the events */
-static void *msg_queue_manager(void * parm)
+/* 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;
-	time_t msg_age = 0;
-	struct timespec tv;
+	struct uevent_msg *loop_msg;
+	struct uevent_msg *tmp_msg;
+	struct sysinfo info;
+	long msg_age = 0;
+	int timeout = event_timeout;
 
-	while (1) {
-		dbg("msg queue manager, next expected is %d", expected_seqnum);
-		pthread_mutex_lock(&msg_lock);
-		pthread_mutex_lock(&exec_lock);
+	dbg("msg queue manager, next expected is %llu", expected_seqnum);
 recheck:
-		list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
-			/* move event with expected sequence to the exec list */
-			if (loop_msg->seqnum == expected_seqnum) {
-				msg_move_exec(&loop_msg->list);
-				expected_seqnum++;
-				dbg("moved seq %d to exec, next expected is %d",
-				    loop_msg->seqnum, expected_seqnum);
-				continue;
-			}
-
-			/* move event with expired timeout to the exec list */
-			msg_age = time(NULL) - loop_msg->queue_time;
-			if (msg_age > EVENT_TIMEOUT_SEC-1) {
-				msg_move_exec(&loop_msg->list);
-				expected_seqnum = loop_msg->seqnum+1;
-				dbg("moved seq %d to exec, reset next expected to %d",
-				    loop_msg->seqnum, expected_seqnum);
-				goto recheck;
-			} else {
-				break;
-			}
+	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) {
+			msg_move_exec(loop_msg);
+			continue;
 		}
 
-		msg_dump_queue();
-		pthread_mutex_unlock(&exec_lock);
-		pthread_mutex_unlock(&msg_lock);
-
-		/* wait until queue gets active or next message timeout expires */
-		pthread_mutex_lock(&msg_active_lock);
+		/* 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);
+		}
 
-		if (list_empty(&msg_list) == 0) {
-			tv.tv_sec = time(NULL) + EVENT_TIMEOUT_SEC - msg_age;
-			tv.tv_nsec = 0;
-			dbg("next event expires in %li seconds",
-			    EVENT_TIMEOUT_SEC - msg_age);
-			pthread_cond_timedwait(&msg_active, &msg_active_lock, &tv);
+		/* move event with expired timeout to the exec list */
+		msg_age = info.uptime - loop_msg->queue_time;
+		dbg("seq %llu is %li seconds old", loop_msg->seqnum, msg_age);
+		if (msg_age >= timeout) {
+			msg_move_exec(loop_msg);
+			goto recheck;
 		} else {
-			pthread_cond_wait(&msg_active, &msg_active_lock);
+			break;
 		}
-		pthread_mutex_unlock(&msg_active_lock);
+	}
+
+	msg_dump_queue();
+
+	/* set timeout for remaining queued events */
+	if (list_empty(&msg_list) == 0) {
+		struct itimerval itv = {{0, 0}, {timeout - msg_age, 0}};
+		dbg("next event expires in %li seconds", timeout - msg_age);
+		setitimer(ITIMER_REAL, &itv, NULL);
 	}
 }
 
-/* every connect creates a thread which gets the msg, queues it and exits */
-static void *client_threads(void * parm)
+static struct uevent_msg *get_msg_from_envbuf(const char *buf, int buf_size)
 {
-	int sock;
-	struct hotplug_msg *msg;
-	int retval;
+	int bufpos;
+	int i;
+	struct uevent_msg *msg;
+	int major = 0;
+	int minor = 0;
+
+	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];
+		else if (strncmp(key, "DEVPATH=", 8) == 0)
+			msg->devpath = &key[8];
+		else if (strncmp(key, "SUBSYSTEM=", 10) == 0)
+			msg->subsystem = &key[10];
+		else if (strncmp(key, "SEQNUM=", 7) == 0)
+			msg->seqnum = strtoull(&key[7], NULL, 10);
+		else if (strncmp(key, "PHYSDEVPATH=", 12) == 0)
+			msg->physdevpath = &key[12];
+		else if (strncmp(key, "MAJOR=", 6) == 0)
+			major = strtoull(&key[6], NULL, 10);
+		else if (strncmp(key, "MINOR=", 6) == 0)
+			minor = strtoull(&key[6], NULL, 10);
+		else if (strncmp(key, "TIMEOUT=", 8) == 0)
+			msg->timeout = strtoull(&key[8], NULL, 10);
+	}
+	msg->devt = makedev(major, minor);
+	msg->envp[i++] = "UDEVD_EVENT=1";
+	msg->envp[i] = NULL;
 
-	sock = (int) parm;
+	return msg;
+}
 
-	msg = msg_create();
-	if (msg == NULL) {
-		dbg("unable to store message");
-		goto exit;
+/* 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;
+	struct iovec iov;
+	struct ucred *cred;
+	char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
+	int envbuf_size;
+	int *intval;
+
+	memset(&usend_msg, 0x00, sizeof(struct udevd_msg));
+	iov.iov_base = &usend_msg;
+	iov.iov_len = sizeof(struct udevd_msg);
+
+	memset(&smsg, 0x00, sizeof(struct msghdr));
+	smsg.msg_iov = &iov;
+	smsg.msg_iovlen = 1;
+	smsg.msg_control = cred_msg;
+	smsg.msg_controllen = sizeof(cred_msg);
+
+	size = recvmsg(udevd_sock, &smsg, 0);
+	if (size <  0) {
+		if (errno != EINTR)
+			dbg("unable to receive udevd message");
+		return NULL;
 	}
+	cmsg = CMSG_FIRSTHDR(&smsg);
+	cred = (struct ucred *) CMSG_DATA(cmsg);
 
-	retval = recv(sock, msg, sizeof(struct hotplug_msg), 0);
-	if (retval <  0) {
-		dbg("unable to receive message");
-		goto exit;
+	if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
+		info("no sender credentials received, message ignored");
+		return NULL;
 	}
 
-	if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
-		dbg("message magic '%s' doesn't match, ignore it", msg->magic);
-		msg_delete(msg);
-		goto exit;
+	if (cred->uid != 0) {
+		info("sender uid=%i, message ignored", cred->uid);
+		return NULL;
+	}
+
+	if (strncmp(usend_msg.magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
+		info("message magic '%s' doesn't match, ignore it", usend_msg.magic);
+		return NULL;
+	}
+
+	switch (usend_msg.type) {
+	case UDEVD_UEVENT_UDEVSEND:
+	case UDEVD_UEVENT_INITSEND:
+		info("udevd event message 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;
+		msg->type = usend_msg.type;
+		return msg;
+	case UDEVD_STOP_EXEC_QUEUE:
+		info("udevd message (STOP_EXEC_QUEUE) received");
+		stop_exec_q = 1;
+		break;
+	case UDEVD_START_EXEC_QUEUE:
+		info("udevd message (START_EXEC_QUEUE) received");
+		stop_exec_q = 0;
+		exec_queue_manager();
+		break;
+	case UDEVD_SET_LOG_LEVEL:
+		intval = (int *) usend_msg.envbuf;
+		info("udevd message (SET_LOG_PRIORITY) received, udev_log_priority=%i", *intval);
+		udev_log_priority = *intval;
+		break;
+	case UDEVD_SET_MAX_CHILDS:
+		intval = (int *) usend_msg.envbuf;
+		info("udevd message (UDEVD_SET_MAX_CHILDS) received, max_childs=%i", *intval);
+		max_childs = *intval;
+		break;
+	default:
+		dbg("unknown message type");
 	}
+	return NULL;
+}
 
-	pthread_mutex_lock(&msg_lock);
-	msg_queue_insert(msg);
-	pthread_mutex_unlock(&msg_lock);
+/* receive the kernel user event message and do some sanity checks */
+static struct uevent_msg *get_netlink_msg(void)
+{
+	struct uevent_msg *msg;
+	int bufpos;
+	ssize_t size;
+	static char buffer[UEVENT_BUFFER_SIZE + 512];
+	char *pos;
+
+	size = recv(uevent_netlink_sock, &buffer, sizeof(buffer), 0);
+	if (size <  0) {
+		if (errno != EINTR)
+			dbg("unable to receive udevd message");
+		return NULL;
+	}
 
-exit:
-	close(sock);
-	pthread_exit(0);
+	if ((size_t)size > sizeof(buffer)-1)
+		size = sizeof(buffer)-1;
+	buffer[size] = '\0';
+	dbg("uevent_size=%zi", size);
+
+	/* start of event payload */
+	bufpos = strlen(buffer)+1;
+	msg = get_msg_from_envbuf(&buffer[bufpos], size-bufpos);
+	if (msg == NULL)
+		return NULL;
+	msg->type = UDEVD_UEVENT_NETLINK;
+
+	/* validate message */
+	pos = strchr(buffer, '@');
+	if (pos == NULL) {
+		dbg("invalid uevent '%s'", buffer);
+		free(msg);
+		return NULL;
+	}
+	pos[0] = '\0';
+
+	if (msg->action == NULL) {
+		dbg("no ACTION in payload found, skip event '%s'", buffer);
+		free(msg);
+		return NULL;
+	}
+
+	if (strcmp(msg->action, buffer) != 0) {
+		dbg("ACTION in payload does not match uevent, skip event '%s'", buffer);
+		free(msg);
+		return NULL;
+	}
+
+	return msg;
 }
 
-static void sig_handler(int signum)
+static void asmlinkage sig_handler(int signum)
 {
+	int rc;
+
 	switch (signum) {
 		case SIGINT:
 		case SIGTERM:
-			unlink(UDEVD_LOCK);
-			unlink(UDEVD_SOCK);
 			exit(20 + signum);
 			break;
-		default:
-			dbg("unhandled signal");
+		case SIGALRM:
+			/* set flag, then write to pipe if needed */
+			run_msg_q = 1;
+			goto do_write;
+			break;
+		case SIGCHLD:
+			/* set flag, then write to pipe if needed */
+			sigchilds_waiting = 1;
+			goto do_write;
+			break;
+	}
+
+do_write:
+	/* if pipe is empty, write to pipe to force select to return
+	 * immediately when it gets called
+	 */
+	if (!sig_flag) {
+		rc = write(pipefds[1],&signum,sizeof(signum));
+		if (rc >= 0)
+			sig_flag = 1;
 	}
 }
 
-static int one_and_only(void)
+static void udev_done(int pid)
 {
-	char string[50];
-	int lock_file;
+	/* find msg associated with pid and delete it */
+	struct uevent_msg *msg;
+	struct sysinfo info;
+
+	list_for_each_entry(msg, &running_list, node) {
+		if (msg->pid == pid) {
+			sysinfo(&info);
+			info("seq %llu exit, %ld seconds old", msg->seqnum, info.uptime - msg->queue_time);
+			msg_queue_delete(msg);
+
+			/* we want to run the exec queue manager since there may
+			 * be events waiting with the devpath of the one that
+			 * just finished
+			 */
+			run_exec_q = 1;
+			return;
+		}
+	}
+}
+
+static void reap_sigchilds(void)
+{
+	while(1) {
+		int pid = waitpid(-1, NULL, WNOHANG);
+		if ((pid == -1) || (pid == 0))
+			break;
+		udev_done(pid);
+	}
+}
+
+/* just read everything from the pipe and clear the flag,
+ * the flags was set in the signal handler
+ */
+static void user_sighandler(void)
+{
+	int sig;
+
+	while(1) {
+		int rc = read(pipefds[0], &sig, sizeof(sig));
+		if (rc < 0)
+			break;
+
+		sig_flag = 0;
+	}
+}
+
+static int init_udevd_socket(void)
+{
+	struct sockaddr_un saddr;
+	const int buffersize = 1024 * 1024;
+	socklen_t addrlen;
+	const int feature_on = 1;
+	int retval;
+
+	memset(&saddr, 0x00, sizeof(saddr));
+	saddr.sun_family = AF_LOCAL;
+	/* use abstract namespace for socket path */
+	strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
+	addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 
-	lock_file = open(UDEVD_LOCK, O_RDWR | O_CREAT, 0x640);
-	if (lock_file < 0)
+	udevd_sock = socket(AF_LOCAL, SOCK_DGRAM, 0);
+	if (udevd_sock == -1) {
+		err("error getting socket, %s", strerror(errno));
 		return -1;
+	}
+
+	/* set receive buffersize */
+	setsockopt(udevd_sock, SOL_SOCKET, SO_RCVBUF, &buffersize, sizeof(buffersize));
 
-	/* see if we can lock */
-	if (lockf(lock_file, F_TLOCK, 0) < 0) {
-		dbg("file is already locked, exit");
-		close(lock_file);
+	/* the bind takes care of ensuring only one copy running */
+	retval = bind(udevd_sock, (struct sockaddr *) &saddr, addrlen);
+	if (retval < 0) {
+		err("bind failed, %s", strerror(errno));
+		close(udevd_sock);
 		return -1;
 	}
 
-	snprintf(string, sizeof(string), "%d\n", getpid());
-	write(lock_file, string, strlen(string));
+	/* enable receiving of the sender credentials */
+	setsockopt(udevd_sock, SOL_SOCKET, SO_PASSCRED, &feature_on, sizeof(feature_on));
 
 	return 0;
 }
 
-int main(int argc, char *argv[])
+static int init_uevent_netlink_sock(void)
 {
-	int ssock;
-	int csock;
-	struct sockaddr_un saddr;
-	struct sockaddr_un caddr;
-	socklen_t clen;
-	pthread_t cli_tid;
-	pthread_t mgr_msg_tid;
-	pthread_t mgr_exec_tid;
+	struct sockaddr_nl snl;
+	const int buffersize = 1024 * 1024;
 	int retval;
 
-	init_logging("udevd");
+	memset(&snl, 0x00, sizeof(struct sockaddr_nl));
+	snl.nl_family = AF_NETLINK;
+	snl.nl_pid = getpid();
+	snl.nl_groups = 0xffffffff;
 
-	/* only let one version of the daemon run at any one time */
-	if (one_and_only() != 0)
-		exit(0);
+	uevent_netlink_sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
+	if (uevent_netlink_sock == -1) {
+		dbg("error getting socket, %s", strerror(errno));
+		return -1;
+	}
 
-	signal(SIGINT, sig_handler);
-	signal(SIGTERM, sig_handler);
+	/* set receive buffersize */
+	setsockopt(uevent_netlink_sock, SOL_SOCKET, SO_RCVBUF, &buffersize, sizeof(buffersize));
 
-	memset(&saddr, 0x00, sizeof(saddr));
-	saddr.sun_family = AF_LOCAL;
-	strcpy(saddr.sun_path, UDEVD_SOCK);
+	retval = bind(uevent_netlink_sock, (struct sockaddr *) &snl,
+		      sizeof(struct sockaddr_nl));
+	if (retval < 0) {
+		dbg("bind failed, %s", strerror(errno));
+		close(uevent_netlink_sock);
+		uevent_netlink_sock = -1;
+		return -1;
+	}
+
+	return 0;
+}
+
+int main(int argc, char *argv[], char *envp[])
+{
+	int maxsockplus;
+	int retval;
+	int fd;
+	struct sigaction act;
+	fd_set readfds;
+	const char *value;
+	int uevent_netlink_active = 0;
+	int daemonize = 0;
+	int i;
+
+	logging_init("udevd");
+	udev_init_config();
+	dbg("version %s", UDEV_VERSION);
+
+	if (getuid() != 0) {
+		err("need to be root, exit");
+		goto exit;
+	}
+
+	for (i = 1 ; i < argc; i++) {
+		char *arg = argv[i];
+		if (strcmp(arg, "--daemon") == 0 || strcmp(arg, "-d") == 0) {
+			info("will daemonize");
+			daemonize = 1;
+		}
+		if (strcmp(arg, "--stop-exec-queue") == 0) {
+			info("will not execute events until START_EXEC_QUEUE is received");
+			stop_exec_q = 1;
+		}
+	}
+	if (daemonize) {
+		pid_t pid;
 
-	unlink(UDEVD_SOCK);
-	ssock = socket(AF_LOCAL, SOCK_STREAM, 0);
-	if (ssock == -1) {
-		dbg("error getting socket");
-		exit(1);
+		pid = fork();
+		switch (pid) {
+		case 0:
+			dbg("damonized fork running");
+			break;
+		case -1:
+			err("fork of daemon failed");
+			goto exit;
+		default:
+			logging_close();
+			exit(0);
+		}
 	}
 
-	retval = bind(ssock, &saddr, sizeof(saddr));
+	/* become session leader */
+	sid = setsid();
+	dbg("our session is %d", sid);
+
+	chdir("/");
+	umask(umask(077) | 022);
+
+	/*set a reasonable scheduling priority for the daemon */
+	setpriority(PRIO_PROCESS, 0, UDEVD_PRIORITY);
+
+	/* Set fds to dev/null */
+	fd = open( "/dev/null", O_RDWR );
+	if (fd >= 0)  {
+		dup2(fd, 0);
+		dup2(fd, 1);
+		dup2(fd, 2);
+		if (fd > 2)
+			close(fd);
+	} else
+		err("error opening /dev/null %s", strerror(errno));
+
+	/* setup signal handler pipe */
+	retval = pipe(pipefds);
 	if (retval < 0) {
-		dbg("bind failed\n");
+		err("error getting pipes: %s", strerror(errno));
 		goto exit;
 	}
 
-	retval = listen(ssock, SOMAXCONN);
+	retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 	if (retval < 0) {
-		dbg("listen failed\n");
+		err("error fcntl on read pipe: %s", strerror(errno));
 		goto exit;
 	}
+	retval = fcntl(pipefds[0], F_SETFD, FD_CLOEXEC);
+	if (retval < 0)
+		err("error fcntl on read pipe: %s", strerror(errno));
 
-	pthread_mutex_init(&msg_lock, NULL);
-	pthread_mutex_init(&msg_active_lock, NULL);
-	pthread_mutex_init(&exec_lock, NULL);
-	pthread_mutex_init(&exec_active_lock, NULL);
-	pthread_mutex_init(&running_lock, NULL);
+	retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
+	if (retval < 0) {
+		err("error fcntl on write pipe: %s", strerror(errno));
+		goto exit;
+	}
+	retval = fcntl(pipefds[1], F_SETFD, FD_CLOEXEC);
+	if (retval < 0)
+		err("error fcntl on write pipe: %s", strerror(errno));
+
+	/* set signal handlers */
+	memset(&act, 0x00, sizeof(struct sigaction));
+	act.sa_handler = (void (*)(int)) sig_handler;
+	sigemptyset(&act.sa_mask);
+	act.sa_flags = SA_RESTART;
+	sigaction(SIGINT, &act, NULL);
+	sigaction(SIGTERM, &act, NULL);
+	sigaction(SIGALRM, &act, NULL);
+	sigaction(SIGCHLD, &act, NULL);
+
+	if (init_uevent_netlink_sock() < 0) {
+		dbg("uevent socket not available");
+ 	}
+
+	if (init_udevd_socket() < 0) {
+		if (errno == EADDRINUSE)
+			dbg("another udevd running, exit");
+		else
+			dbg("error initialising udevd socket: %s", strerror(errno));
 
-	/* set default attributes for created threads */
-	pthread_attr_init(&thr_attr);
-	pthread_attr_setdetachstate(&thr_attr, PTHREAD_CREATE_DETACHED);
-	pthread_attr_setstacksize(&thr_attr, 16 * 1024);
+		goto exit;
+	}
 
-	/* init queue management */
-	pthread_create(&mgr_msg_tid, &thr_attr, msg_queue_manager, NULL);
-	pthread_create(&mgr_exec_tid, &thr_attr, exec_queue_manager, NULL);
+	/* 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;
+
+	/* 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);
+	}
 
-	clen = sizeof(caddr);
-	/* main loop */
+	/* 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(udevd_sock, &readfds);
+	if (uevent_netlink_sock != -1)
+		FD_SET(uevent_netlink_sock, &readfds);
+	FD_SET(pipefds[0], &readfds);
+	maxsockplus = udevd_sock+1;
 	while (1) {
-		csock = accept(ssock, &caddr, &clen);
-		if (csock < 0) {
-			dbg("client accept failed\n");
+		struct uevent_msg *msg;
+
+		fd_set workreadfds = readfds;
+		retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
+
+		if (retval < 0) {
+			if (errno != EINTR)
+				dbg("error in select: %s", strerror(errno));
 			continue;
 		}
-		pthread_create(&cli_tid, &thr_attr, client_threads, (void *) csock);
+
+		if (FD_ISSET(udevd_sock, &workreadfds)) {
+			msg = get_udevd_msg();
+			if (msg) {
+				/* discard kernel messages if netlink is active */
+				if (uevent_netlink_active && msg->type == UDEVD_UEVENT_UDEVSEND && msg->seqnum != 0) {
+					dbg("skip uevent_helper message, netlink is active");
+					free(msg);
+					continue;
+				}
+				msg_queue_insert(msg);
+			}
+		}
+
+		if (FD_ISSET(uevent_netlink_sock, &workreadfds)) {
+			msg = get_netlink_msg();
+			if (msg) {
+				msg_queue_insert(msg);
+				/* disable udevsend with first netlink message */
+				if (!uevent_netlink_active) {
+					info("uevent_nl message received, disable udevsend messages");
+					uevent_netlink_active = 1;
+				}
+			}
+		}
+
+		if (FD_ISSET(pipefds[0], &workreadfds))
+			user_sighandler();
+
+		if (sigchilds_waiting) {
+			sigchilds_waiting = 0;
+			reap_sigchilds();
+		}
+
+		if (run_msg_q) {
+			run_msg_q = 0;
+			msg_queue_manager();
+		}
+
+		if (run_exec_q) {
+			 /* clean up running_list before calling exec_queue_manager() */
+			if (sigchilds_waiting) {
+				sigchilds_waiting = 0;
+				reap_sigchilds();
+			}
+
+			run_exec_q = 0;
+			if (!stop_exec_q)
+				exec_queue_manager();
+		}
 	}
+
 exit:
-	close(ssock);
-	unlink(UDEVD_SOCK);
-	exit(1);
+	logging_close();
+	return 1;
 }