[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, 3 insertions, 0 deletions

diff --git a/udev.h b/udev.h
index 46c961c2d5..d66e9f626e 100644
--- a/udev.h
+++ b/udev.h
@@ -26,6 +26,9 @@
 #include <sys/param.h>
 #include "libsysfs/sysfs/libsysfs.h"
 
+#define ALARM_TIMEOUT			30
+#define WAIT_FOR_FILE_SECONDS		10
+#define WAIT_FOR_FILE_RETRY_FREQ	10
 #define COMMENT_CHARACTER		'#'
 
 #define NAME_SIZE			256