From: Michael S. Tsirkin <mst@redhat.com>
Date: Tue, 10 Mar 2015 01:25:08 +0000 (+1030)
Subject: virtio-balloon: do not call blocking ops when !TASK_RUNNING
X-Git-Tag: omap-for-v4.1/fixes-rc1~315^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3d2a3774c1b046f548ebea0391a602fd5685a307;p=pandora-kernel.git

virtio-balloon: do not call blocking ops when !TASK_RUNNING

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 <thuth@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Thomas Huth <thuth@linux.vnet.ibm.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---

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