This is a note to let you know that I've just added the patch titled
virtio_balloon: don't softlockup on huge balloon changes.
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
virtio_balloon-don-t-softlockup-on-huge-balloon-changes.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 1f74ef0f2d7d692fcd615621e0e734c3e7771413 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Date: Thu, 13 Mar 2014 11:23:38 +1030
Subject: virtio_balloon: don't softlockup on huge balloon changes.
From: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
}
Patches currently in stable-queue which might be from rusty@xxxxxxxxxxxxxxx are
queue-3.14/virtio_balloon-don-t-softlockup-on-huge-balloon-changes.patch
queue-3.14/tools-virtio-add-a-missing.patch
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