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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>
This commit is contained in:
Michael S. Tsirkin 2015-03-10 11:55:08 +10:30 committed by Rusty Russell
parent 0fa2a56437
commit 3d2a3774c1
1 changed files with 14 additions and 5 deletions
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19
drivers/virtio/virtio_balloon.c
View File

@ -29,6 +29,7 @@
#include <linux/module.h>
#include <linux/balloon_compaction.h>
#include <linux/oom.h>
#include <linux/wait.h>
/*
* Balloon device works in 4K page units. So each page is pointed to by
@ -334,17 +335,25 @@ static int virtballoon_oom_notify(struct notifier_block *self,
static int balloon(void *_vballoon)
{
struct virtio_balloon *vb = _vballoon;
DEFINE_WAIT_FUNC(wait, woken_wake_function);
set_freezable();
while (!kthread_should_stop()) {
s64 diff;
try_to_freeze();
wait_event_interruptible(vb->config_change,
(diff = towards_target(vb)) != 0
|| vb->need_stats_update
|| kthread_should_stop()
|| freezing(current));
add_wait_queue(&vb->config_change, &wait);
for (;;) {
if ((diff = towards_target(vb)) != 0 ||
vb->need_stats_update ||
kthread_should_stop() ||
freezing(current))
break;
wait_woken(&wait, TASK_INTERRUPTIBLE, MAX_SCHEDULE_TIMEOUT);
}
remove_wait_queue(&vb->config_change, &wait);
if (vb->need_stats_update)
stats_handle_request(vb);
if (diff > 0)