[PATCH] udev - next round of udev event order daemon

Here is the next round of udevd/udevsend:

udevsend - If the IPC message we send is not catched by a receiver we fork
           the udevd daemon to process this and the following events

udevd    - We reorder the events we receive and execute our current udev for
           every event. If one or more events are missing, we wait
           10 seconds and then go ahead in the queue.
           If the queue is empty and we don't receive any event for the next
           30 seconds, the daemon exits.
           The next incoming event will fork the daemon again.

config   - The path's to the executable are specified in udevd.h
           Now they are pointing to the current directory only.


I don't like daemons hiding secrets (and mem leaks :)) inside,
so I want to try this model. It should be enough logic to get all possible
hotplug events executed in the right order.

If no event, then no daemon! So everybody should be happy :)


Here we see:
  1. the daemon fork,
  2. the udev work,
  3. the 10 sec timeout and the skipped events,
  4. the udev work,
     ...,
  5. and the 30 sec timeout and exit.

EVENTS:
  pim:/home/kay/src/udev.kay# test/udevd_test.sh
  pim:/home/kay/src/udev.kay# SEQNUM=15 ./udevsend block
  pim:/home/kay/src/udev.kay# SEQNUM=16 ./udevsend block
  pim:/home/kay/src/udev.kay# SEQNUM=17 ./udevsend block
  pim:/home/kay/src/udev.kay# SEQNUM=18 ./udevsend block
  pim:/home/kay/src/udev.kay# SEQNUM=20 ./udevsend block
  pim:/home/kay/src/udev.kay# SEQNUM=21 ./udevsend block


LOG:
  Jan 23 15:35:35 pim udev[11795]: message is still in the ipc queue, starting daemon...
  Jan 23 15:35:35 pim udev[11799]: configured rule in '/etc/udev/udev.rules' at line 19 applied, 'sda' becomes '%k-flash'
  Jan 23 15:35:35 pim udev[11799]: creating device node '/udev/sda-flash'
  Jan 23 15:35:35 pim udev[11800]: creating device node '/udev/sdb'
  Jan 23 15:35:35 pim udev[11804]: creating device node '/udev/sdc'
  Jan 23 15:35:35 pim udev[11805]: removing device node '/udev/sda-flash'
  Jan 23 15:35:35 pim udev[11808]: removing device node '/udev/sdb'
  Jan 23 15:35:35 pim udev[11809]: removing device node '/udev/sdc'
  Jan 23 15:35:45 pim udev[11797]: timeout reached, skip events 7 - 7
  Jan 23 15:35:45 pim udev[11811]: creating device node '/udev/sdb'
  Jan 23 15:35:45 pim udev[11812]: creating device node '/udev/sdc'
  Jan 23 15:36:01 pim udev[11797]: timeout reached, skip events 10 - 14
  Jan 23 15:36:01 pim udev[11814]: creating device node '/udev/sdc'
  Jan 23 15:36:04 pim udev[11816]: creating device node '/udev/sdc'
  Jan 23 15:36:12 pim udev[11818]: creating device node '/udev/sdc'
  Jan 23 15:36:16 pim udev[11820]: creating device node '/udev/sdc'
  Jan 23 15:36:38 pim udev[11797]: timeout reached, skip events 19 - 19
  Jan 23 15:36:38 pim udev[11823]: creating device node '/udev/sdc'
  Jan 23 15:36:38 pim udev[11824]: creating device node '/udev/sdc'
  Jan 23 15:37:08 pim udev[11797]: we have nothing to do, so daemon exits...

4 files changed, 133 insertions, 122 deletions

diff --git a/test/udevd_test.sh b/test/udevd_test.sh
index 013cdb9d6c..0c7bd431be 100644
--- a/test/udevd_test.sh
+++ b/test/udevd_test.sh
@@ -1,47 +1,52 @@
 #!/bin/bash
 
-# reset udevd, expected sequence number and empty queue
-killall -HUP udevd
+# kill daemon, first event will start it again
+killall udevd
 
-export ACTION=add
-export DEVPATH=/block/sda
+# connect(123) - disconnect(456) - connect(789) sequence of sda/sdb/sdc
 
 export SEQNUM=1
+export ACTION=add
+export DEVPATH=/block/sda
 ./udevsend block
 
 export SEQNUM=2
-./udevsend block
-
-export SEQNUM=3
-./udevsend block
-
-export SEQNUM=5
+export ACTION=add
+export DEVPATH=/block/sdb
 ./udevsend block
 
 export SEQNUM=4
+export ACTION=remove
+export DEVPATH=/block/sda
 ./udevsend block
 
-export SEQNUM=6
+export SEQNUM=3
+export ACTION=add
+export DEVPATH=/block/sdc
 ./udevsend block
 
-export SEQNUM=7
+export SEQNUM=6
+export ACTION=remove
+export DEVPATH=/block/sdc
 ./udevsend block
 
-export SEQNUM=10
+export SEQNUM=5
+export ACTION=remove
+export DEVPATH=/block/sdb
 ./udevsend block
 
-export SEQNUM=9
-#./udevsend block
-
-export SEQNUM=8
+export SEQNUM=7
+export ACTION=add
+export DEVPATH=/block/sda
 #./udevsend block
 
-export SEQNUM=13
-./udevsend block
-
-export SEQNUM=12
+export SEQNUM=9
+export ACTION=add
+export DEVPATH=/block/sdc
 ./udevsend block
 
-export SEQNUM=11
+export SEQNUM=8
+export ACTION=add
+export DEVPATH=/block/sdb
 ./udevsend block
 
diff --git a/udevd.c b/udevd.c
index 6af265a389..da887ec29b 100644
--- a/udevd.c
+++ b/udevd.c
@@ -37,49 +37,20 @@
 #include "udevd.h"
 #include "logging.h"
 
-#define BUFFER_SIZE		1024
-#define TIMEOUT_SECONDS		10
-
-static void reset_timer(void);
-static void reset_queue(void);
+#define BUFFER_SIZE			1024
+#define EVENT_TIMEOUT_SECONDS		10
+#define DAEMON_TIMEOUT_SECONDS		30
 
 
 static int expect_seqnum = 0;
-static int timeout_value = TIMEOUT_SECONDS;
-static int timeout = 0;
 static struct hotplug_msg *head = NULL;
-static char exec_program[100];
-
-
-static void sig_handler(int signum)
-{
-	dbg("caught signal %d", signum);
-	switch (signum) {
-		case SIGHUP:
-			dbg("reset requested, all waiting events killed");
-			reset_timer();
-			reset_queue();
-			timeout = 0;
-			expect_seqnum = 0;
-			break;
-
-		case SIGINT:
-		case SIGTERM:
-		case SIGKILL:
-			exit(20 + signum);
-			break;
 
-		default:
-			dbg("unhandled signal");
-	}
-}
 
 static void sig_alarmhandler(int signum)
 {
 	dbg("caught signal %d", signum);
 	switch (signum) {
 	case SIGALRM:
-		timeout = 1;
 		dbg("event timeout reached");
 		break;
 
@@ -94,9 +65,9 @@ static void dump_queue(void)
 	p = head;
 
 	dbg("next expected sequence is %d", expect_seqnum);
-	while(p) {
+	while(p != NULL) {
 		dbg("sequence %d in queue", p->seqnum);
-		p=p->next;
+		p = p->next;
 	}
 }
 
@@ -110,59 +81,37 @@ static int dispatch_msg(struct hotplug_msg *pmsg)
 {
 	pid_t pid;
 	char *argv[3];
-	int retval;
 	extern char **environ;
 
 	dump_msg(pmsg);
-	dbg("exec '%s'", exec_program);
 
 	setenv("ACTION", pmsg->action, 1);
 	setenv("DEVPATH", pmsg->devpath, 1);
-
-	argv[0] = exec_program;
+	argv[0] = DEFAULT_UDEV_EXEC;
 	argv[1] = pmsg->subsystem;
 	argv[2] = NULL;
 
 	pid = fork();
 	switch (pid) {
 	case 0:
-		retval = execve(argv[0], argv, environ);
-		if (retval != 0) {
-			dbg("child execve failed");
-			exit(1);
-		}
+		/* child */
+		execve(argv[0], argv, environ);
+		dbg("exec of child failed");
+		exit(1);
 		break;
 	case -1:
-		dbg("fork failed");
+		dbg("fork of child failed");
 		return -1;
 	default:
 		wait(0);
-		break;
 	}
 	return 0;
 }
 
-static void reset_timer(void)
-{
-	alarm(0);
-}
-
-static void set_timer(void)
+static void set_timer(int seconds)
 {
 	signal(SIGALRM, sig_alarmhandler);
-	alarm(timeout_value);
-}
-
-static void reset_queue(void)
-{
-	struct hotplug_msg *p;
-	p = head;
-
-	while(head) {
-		p = head;
-		head = head->next;
-		free(p);
-	}
+	alarm(seconds);
 }
 
 static void check_queue(void)
@@ -171,7 +120,7 @@ static void check_queue(void)
 	p = head;
 
 	dump_queue();
-	while(head && head->seqnum == expect_seqnum) {
+	while(head != NULL && head->seqnum == expect_seqnum) {
 		dispatch_msg(head);
 		expect_seqnum++;
 		p = head;
@@ -179,9 +128,9 @@ static void check_queue(void)
 		free(p);
 	}
 	if (head != NULL)
-		set_timer();
+		set_timer(EVENT_TIMEOUT_SECONDS);
 	else
-		reset_timer();
+		set_timer(DAEMON_TIMEOUT_SECONDS);
 }
 
 static void add_queue(struct hotplug_msg *pmsg)
@@ -195,7 +144,7 @@ static void add_queue(struct hotplug_msg *pmsg)
 	pnewmsg = malloc(sizeof(struct hotplug_msg));
 	*pnewmsg = *pmsg;
 	pnewmsg->next = NULL;
-	while(p && pmsg->seqnum > p->seqnum) {
+	while(p != NULL && pmsg->seqnum > p->seqnum) {
 		p1 = p;
 		p = p->next;
 	}
@@ -216,12 +165,12 @@ static int process_queue(void)
 	char buf[BUFFER_SIZE];
 	int ret;
 
-	key = ftok(DEFAULT_EXEC_PROGRAM, IPC_KEY_ID);
+	key = ftok(DEFAULT_UDEVD_EXEC, IPC_KEY_ID);
 	pmsg = (struct hotplug_msg *) buf;
 	msgid = msgget(key, IPC_CREAT);
 	if (msgid == -1) {
 		dbg("open message queue error");
-		goto exit;
+		return -1;
 	}
 	while (1) {
 		ret = msgrcv(msgid, (struct msgbuf *) buf, BUFFER_SIZE-4, HOTPLUGMSGTYPE, 0);
@@ -236,7 +185,7 @@ static int process_queue(void)
 
 			if (pmsg->seqnum > expect_seqnum) {
 				add_queue(pmsg);
-				set_timer();
+				set_timer(EVENT_TIMEOUT_SECONDS);
 			} else {
 				if (pmsg->seqnum == expect_seqnum) {
 					dispatch_msg(pmsg);
@@ -246,37 +195,49 @@ static int process_queue(void)
 					dbg("timeout event for unexpected sequence number %d", pmsg->seqnum);
 				}
 			}
-		} else
+		} else {
 			if (errno == EINTR) {
 				if (head != NULL) {
-					/* timeout, skip all missing, proceed with next queued event */
-					dbg("timeout reached, skip events %d - %d", expect_seqnum, head->seqnum-1);
+					/* event timeout, skip all missing, proceed with next queued event */
+					info("timeout reached, skip events %d - %d", expect_seqnum, head->seqnum-1);
 					expect_seqnum = head->seqnum;
+				} else {
+					info("we have nothing to do, so daemon exits...");
+					exit(0);
 				}
 				check_queue();
-				timeout = 0;
 			} else {
 				dbg("ipc message receive error '%s'", strerror(errno));
 			}
+		}
 	}
 	return 0;
-exit:
-	return -1;
 }
 
-int main(int argc, char *argv[])
+static void sig_handler(int signum)
 {
-	/* get program to exec on events */
-	if (argc == 2)
-		strncpy(exec_program, argv[1], sizeof(exec_program));
-	else
-		strcpy(exec_program, DEFAULT_EXEC_PROGRAM);
+	dbg("caught signal %d", signum);
+	switch (signum) {
+		case SIGINT:
+		case SIGTERM:
+		case SIGKILL:
+			exit(20 + signum);
+			break;
+
+		default:
+			dbg("unhandled signal");
+	}
+}
 
+int main(int argc, char *argv[])
+{
 	/* set up signal handler */
 	signal(SIGINT, sig_handler);
 	signal(SIGTERM, sig_handler);
 	signal(SIGKILL, sig_handler);
-	signal(SIGHUP, sig_handler);
+
+	/* we exit if we have nothing to do, next event will start us again */
+	set_timer(DAEMON_TIMEOUT_SECONDS);
 
 	/* main loop */
 	process_queue();
diff --git a/udevd.h b/udevd.h
index eb516ab65d..43fe6b421a 100644
--- a/udevd.h
+++ b/udevd.h
@@ -21,9 +21,11 @@
  *
  */
 
-#define HOTPLUGMSGTYPE		44
-#define DEFAULT_EXEC_PROGRAM	"/sbin/udev"
+#define DEFAULT_UDEV_EXEC	"./udev"
+#define DEFAULT_UDEVD_EXEC	"./udevd"
+
 #define IPC_KEY_ID		0
+#define HOTPLUGMSGTYPE		44
 
 
 struct hotplug_msg {
diff --git a/udevsend.c b/udevsend.c
index 748c8f2217..d3e5378285 100644
--- a/udevsend.c
+++ b/udevsend.c
@@ -29,6 +29,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
+#include <time.h>
+#include <wait.h>
 
 #include "udev.h"
 #include "udevd.h"
@@ -78,6 +81,39 @@ static void free_hotplugmsg(struct hotplug_msg *pmsg)
 	free(pmsg);
 }
 
+static int start_daemon(void)
+{
+	pid_t pid;
+	pid_t child_pid;
+
+	pid = fork();
+	switch (pid) {
+	case 0:
+		/* helper child */
+		child_pid = fork();
+		switch (child_pid) {
+		case 0:
+			/* daemon */
+			execl(DEFAULT_UDEVD_EXEC, NULL);
+			dbg("exec of daemon failed");
+			exit(1);
+		case -1:
+			dbg("fork of daemon failed");
+			return -1;
+		default:
+			exit(0);
+		}
+		break;
+	case -1:
+		dbg("fork of helper failed");
+		return -1;
+	default:
+		wait(0);
+	}
+	return 0;
+}
+
+
 int main(int argc, char* argv[])
 {
 	int msgid;
@@ -91,6 +127,8 @@ int main(int argc, char* argv[])
 	int seq;
 	int retval = -EINVAL;
 	int size;
+	int loop;
+	struct timespec tspec;
 
 	subsystem = argv[1];
 	if (subsystem == NULL) {
@@ -118,7 +156,7 @@ int main(int argc, char* argv[])
 	seq = atoi(seqnum);
 
 	/* create ipc message queue or get id of our existing one */
-	key = ftok(DEFAULT_EXEC_PROGRAM, IPC_KEY_ID);
+	key = ftok(DEFAULT_UDEVD_EXEC, IPC_KEY_ID);
 	size =  build_hotplugmsg( (struct hotplug_msg**) &pmsg, action, devpath, subsystem, seq);
 	msgid = msgget(key, IPC_CREAT);
 	if (msgid == -1) {
@@ -126,15 +164,6 @@ int main(int argc, char* argv[])
 		goto exit;
 	}
 
-	/* get state of ipc queue */
-	retval = msgctl(msgid, IPC_STAT, &msg_queue);
-	if (retval == -1) {
-		dbg("error getting info on ipc queue");
-		goto exit;
-	}
-	if (msg_queue.msg_qnum > 0)
-		dbg("%li messages already in the ipc queue", msg_queue.msg_qnum);
-
 	/* send ipc message to the daemon */
 	retval = msgsnd(msgid, pmsg, size, 0);
 	free_hotplugmsg( (struct hotplug_msg*) pmsg);
@@ -142,11 +171,25 @@ int main(int argc, char* argv[])
 		dbg("error sending ipc message");
 		goto exit;
 	}
-	return 0;
 
-exit:
-	if (retval > 0)
-		retval = 0;
+	/* get state of ipc queue */
+	tspec.tv_sec = 0;
+	tspec.tv_nsec = 10000000;  /* 10 millisec */
+	loop = 20;
+	while (loop--) {
+		retval = msgctl(msgid, IPC_STAT, &msg_queue);
+		if (retval == -1) {
+			dbg("error getting info on ipc queue");
+			goto exit;
+		}
+		if (msg_queue.msg_qnum == 0)
+			goto exit;
+		nanosleep(&tspec, NULL);
+	}
 
+	info("message is still in the ipc queue, starting daemon...");
+	retval = start_daemon();
+
+exit:
 	return retval;
 }