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virtio_balloon: don't softlockup on huge balloon changes.

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commit 1f74ef0f2d 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>
This commit is contained in:
Rusty Russell 2014-03-13 11:23:38 +10:30 committed by Greg Kroah-Hartman
parent a93daee35a
commit 16440b5497
1 changed files with 6 additions and 0 deletions
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6
drivers/virtio/virtio_balloon.c
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@ -311,6 +311,12 @@ 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;
}