Re: [PATCH v2] virtio-balloon: do not call blocking ops when !TASK_RUNNING
From: Cornelia Huck <hidden>
Date: 2015-02-25 15:11:38
Also in:
kvm, lkml, stable
On Wed, 25 Feb 2015 15:36:02 +0100 "Michael S. Tsirkin" [off-list ref] wrote:
virtio balloon has this code:
wait_event_interruptible(vb->config_change,
(diff = towards_target(vb)) != 0
|| vb->need_stats_update
|| kthread_should_stop()
|| freezing(current));
Which is a problem because towards_target() call might block after
wait_event_interruptible sets task state to TAST_INTERRUPTIBLE, causing
the task_struct::state collision typical of nesting of sleeping
primitives
See also http://lwn.net/Articles/628628/ or Thomas's
bug report
http://article.gmane.org/gmane.linux.kernel.virtualization/24846
for a fuller explanation.
To fix, rewrite using wait_woken.
Cc: stable@vger.kernel.org
Reported-by: Thomas Huth <redacted>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
changes from v1:
remove wait_event_interruptible
noticed by Cornelia Huck [off-list ref]
drivers/virtio/virtio_balloon.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)I was able to reproduce Thomas' original problem and can confirm that it is gone with this patch. Reviewed-by: Cornelia Huck <redacted>