This is a note to let you know that I've just added the patch titled
virtio-balloon: do not call blocking ops when !TASK_RUNNING
to the 3.19-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-do-not-call-blocking-ops-when-task_running.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3d2a3774c1b046f548ebea0391a602fd5685a307 Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Date: Tue, 10 Mar 2015 11:55:08 +1030
Subject: virtio-balloon: do not call blocking ops when !TASK_RUNNING
From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
commit 3d2a3774c1b046f548ebea0391a602fd5685a307 upstream.
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.
Reported-by: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Tested-by: Thomas Huth <thuth@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_balloon.c | 19 ++++++++++++++-----
1 file changed, 14 insertions(+), 5 deletions(-)
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -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
@@ -335,17 +336,25 @@ static int virtballoon_oom_notify(struct
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)
Patches currently in stable-queue which might be from mst@xxxxxxxxxx are
queue-3.19/virtio-balloon-do-not-call-blocking-ops-when-task_running.patch
queue-3.19/virtio_balloon-set-driver_ok-before-using-device.patch
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