I recently encountered a situation where an unclean ebtables shutdown
caused /var/lib/ebtables/lock to be left behind. When libvirtd was
started on such a system, it caused libvirtd to "hang". Reason:
While probing to check if locking was supported, libvirt runs this
command synchronously :
# /usr/sbin/ebtables --concurrent -L
And this seemed to go on with msgs like :
Trying to obtain lock /var/lib/ebtables/lock
Trying to obtain lock /var/lib/ebtables/lock
Trying to obtain lock /var/lib/ebtables/lock
Result:
Libvirtd never recovered from this scenario, and the system was
essentially unable to start any VMs.
The following patch fixes this scenario:
-----------------------------------------------------------
>From ec245eccc03e8a69dc2c2e6edbf30a7b34eb74d0 Mon Sep 17 00:00:00 2001
From: Prerna Saxena <prerna@xxxxxxxxxxxxxxxxxx>
Date: Fri, 26 Dec 2014 15:24:45 -0500
Subject: [PATCH] Firewall : let libvirtd proceed after verifying valid locking
args.
Commit dc33e6e4a5a5d42 introduces locking args to be run with [eb/ip]tables to
determine whether locking is supported. However, this command needs to be
run asynchronously ( as against its present synchronous run), and needs to be
gracefully terminated once the job is done. Else it can potentially stall libvirtd
with messages like :
"Trying to acquire lock ..."
Signed-off-by: Prerna Saxena <prerna@xxxxxxxxxxxxxxxxxx>
---
src/util/virfirewall.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/src/util/virfirewall.c b/src/util/virfirewall.c
index b536912..c120717 100644
--- a/src/util/virfirewall.c
+++ b/src/util/virfirewall.c
@@ -121,12 +121,16 @@ virFirewallCheckUpdateLock(bool *lockflag,
{
int status; /* Ignore failed commands without logging them */
virCommandPtr cmd = virCommandNewArgs(args);
- if (virCommandRun(cmd, &status) < 0 || status) {
+ status = virCommandRunAsync(cmd, NULL);
+ if (status < 0) {
VIR_INFO("locking not supported by %s", args[0]);
+ goto cleanup;
} else {
VIR_INFO("using locking for %s", args[0]);
*lockflag = true;
}
+cleanup:
+ virCommandAbort(cmd);
virCommandFree(cmd);
}
--
1.8.4.2
Regards,
----------
Prerna Saxena,
IBM Systems & technology Labs,
Bangalore
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