[PATCH] prevent deadlocks on an corrupt udev database

Here is the patch, that should prevent all of the known deadlocks with
corrupt tdb databases we discovered.
Thanks to Frank Steiner <fsteiner-mail@bio.ifi.lmu.de>, who tested all this
endlessly with a NFS mounted /dev. The conclusion is, that udev will not work
on filesystems without proper record locking, but we should prevent the
endless loops anyway. This patch implements:

o recovery from a corrupted udev database. udev will continue
  without database support now, instead of doing nothing. So the node should
  be generated in any case, remove will obviously not work for custom names.

o added iteration limits to the tdb-code at the places we discovered endless
  loops. In the case tdb tries to find more than 100.000 entries with the
  same hash, we better give up :)

o prevent a {all_partitions} loop caused by corrupt db data

o log all tdb errors to syslog

o switch sleep() to usleep() cause we want to use alarm()

1 files changed, 8 insertions, 14 deletions

diff --git a/namedev.c b/namedev.c
index 695fb55413..9276b0cbba 100644
--- a/namedev.c
+++ b/namedev.c
@@ -29,7 +29,6 @@
 #include <ctype.h>
 #include <unistd.h>
 #include <errno.h>
-#include <time.h>
 #include <sys/wait.h>
 #include <sys/stat.h>
 #include <sys/sysinfo.h>
@@ -353,7 +352,6 @@ static struct bus_file {
 	{}
 };
 
-#define SECONDS_TO_WAIT_FOR_FILE	10
 static void wait_for_device_to_initialize(struct sysfs_device *sysfs_device)
 {
 	/* sleep until we see the file for this specific bus type show up this
@@ -367,14 +365,14 @@ static void wait_for_device_to_initialize(struct sysfs_device *sysfs_device)
 	struct bus_file *b = &bus_files[0];
 	struct sysfs_attribute *tmpattr;
 	int found = 0;
-	int loop = SECONDS_TO_WAIT_FOR_FILE;
+	int loop = WAIT_FOR_FILE_SECONDS * WAIT_FOR_FILE_RETRY_FREQ;
 
 	while (1) {
 		if (b->bus == NULL) {
 			if (!found)
 				break;
-			/* sleep to give the kernel a chance to create the file */
-			sleep(1);
+			/* give the kernel a chance to create the file */
+			usleep(1000 * 1000 / WAIT_FOR_FILE_RETRY_FREQ);
 			--loop;
 			if (loop == 0)
 				break;
@@ -394,7 +392,8 @@ static void wait_for_device_to_initialize(struct sysfs_device *sysfs_device)
 	}
 	if (!found)
 		dbg("did not find bus type '%s' on list of bus_id_files, "
-		    "contact greg@kroah.com", sysfs_device->bus);
+		    "please report to <linux-hotplug-devel@lists.sourceforge.net>",
+		    sysfs_device->bus);
 exit:
 	return; /* here to prevent compiler warning... */
 }
@@ -680,7 +679,6 @@ static struct sysfs_device *get_sysfs_device(struct sysfs_class_device *class_de
 {
 	struct sysfs_device *sysfs_device;
 	struct sysfs_class_device *class_dev_parent;
-	struct timespec tspec;
 	int loop;
 
 	/* Figure out where the device symlink is at.  For char devices this will
@@ -696,16 +694,14 @@ static struct sysfs_device *get_sysfs_device(struct sysfs_class_device *class_de
 	if (class_dev_parent != NULL) 
 		dbg("given class device has a parent, use this instead");
 
-	tspec.tv_sec = 0;
-	tspec.tv_nsec = 10000000;  /* sleep 10 millisec */
-	loop = 10;
+	loop = WAIT_FOR_FILE_SECONDS * WAIT_FOR_FILE_RETRY_FREQ;
 	while (loop--) {
 		if (udev_sleep) {
 			if (whitelist_search(class_dev)) {
 				sysfs_device = NULL;
 				goto exit;
 			}
-			nanosleep(&tspec, NULL);
+			usleep(1000 * 1000 / WAIT_FOR_FILE_RETRY_FREQ);
 		}
 
 		if (class_dev_parent)
@@ -727,11 +723,9 @@ device_found:
 		if (sysfs_device->bus[0] != '\0')
 			goto bus_found;
 
-		loop = 10;
-		tspec.tv_nsec = 10000000;
 		while (loop--) {
 			if (udev_sleep)
-				nanosleep(&tspec, NULL);
+				usleep(1000 * 1000 / WAIT_FOR_FILE_RETRY_FREQ);
 			sysfs_get_device_bus(sysfs_device);
 			
 			if (sysfs_device->bus[0] != '\0')