From: Rusty Russell <[email protected]>
This patch does NOT apply to the 3.12 stable tree. If you still want
it applied, please provide a backport.
===============
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 <[email protected]>
Cc: [email protected]
Signed-off-by: Rusty Russell <[email protected]>
---
drivers/virtio/virtio_balloon.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index 34bdabaecbd6..36e7859a31aa 100644
--- 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;
}
--
1.9.3
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