From 841977fc9c3432702c296d6239e4a54291a6007a Mon Sep 17 00:00:00 2001 From: Hannes Reinecke Date: Tue, 24 Jun 2014 08:49:15 +0200 Subject: [PATCH] libmultipath: use a shared lock to co-operate with udev udev since v214 is placing a shared lock on the device node whenever it's processing the event. This introduces a race condition with multipathd, as multipathd is processing the event for the block device at the same time as udev is processing the events for the partitions. And a lock on the partitions will also be visible on the block device itself, hence multipathd won't be able to lock the device. When multipath manages to take a lock on the device, udev will fail, and consequently ignore this entire event. Which in turn might cause the system to malfunction as it might have been a crucial event like 'remove' or 'link down'. So we should better use LOCK_SH here; with that the flock call in multipathd _and_ udev will succeed and the events can be processed. References: bnc#883878 Signed-off-by: Hannes Reinecke diff --git a/libmultipath/configure.c b/libmultipath/configure.c index 0ddd3d5..dc2ebf0 100644 --- a/libmultipath/configure.c +++ b/libmultipath/configure.c @@ -529,7 +529,7 @@ lock_multipath (struct multipath * mpp, int lock) if (!pgp->paths) continue; vector_foreach_slot(pgp->paths, pp, j) { - if (lock && flock(pp->fd, LOCK_EX | LOCK_NB) && + if (lock && flock(pp->fd, LOCK_SH | LOCK_NB) && errno == EWOULDBLOCK) goto fail; else if (!lock)