Commit 1f74ef0f authored Mar 13, 2014 by Rusty Russell

virtio_balloon: don't softlockup on huge balloon changes.



When adding or removing 100G from a balloon:

    BUG: soft lockup - CPU#0 stuck for 22s! [vballoon:367]

We have a wait_event_interruptible(), but the condition is always true
(more ballooning to do) so we don't ever sleep.  We also have a
wait_event() for the host to ack, but that is also always true as QEMU
is synchronous for balloon operations.

Reported-by: Gopesh Kumar Chaudhary <gopchaud@in.ibm.com>
Cc: stable@kernel.org
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

parent 5e37f670

drivers/virtio/virtio_balloon.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -310,6 +310,12 @@ static int balloon(void *_vballoon)
		else if (diff < 0)
		leak_balloon(vb, -diff);
		update_balloon_size(vb);

		/*
		* For large balloon changes, we could spend a lot of time
		* and always have work to do. Be nice if preempt disabled.
		*/
		cond_resched();
		}
		return 0;
		}