| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.14 14/83] virtio_balloon: dont softlockup on huge balloon changes. | Date | Sun, 11 May 2014 21:19:15 +0200 |
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3.14-stable review patch. If anyone has any objections, please let me know.
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From: Rusty Russell <rusty@rustcorp.com.au>
commit 1f74ef0f2d7d692fcd615621e0e734c3e7771413 upstream.
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> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/virtio/virtio_balloon.c | 6 ++++++ 1 file changed, 6 insertions(+)
--- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -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; }
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