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.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
libmultipath/configure.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libmultipath/configure.c b/libmultipath/configure.c
index 30c7259..ca20ba5 100644
--- a/libmultipath/configure.c
+++ b/libmultipath/configure.c
@@ -546,7 +546,7 @@ 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)
--
2.6.6
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