From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Thomas Huth , "Michael S. Tsirkin" , Cornelia Huck , Rusty Russell Subject: [PATCH 3.19 20/75] virtio-balloon: do not call blocking ops when !TASK_RUNNING Date: Fri, 10 Apr 2015 15:18:46 +0200 Message-Id: <20150410131708.958870471@linuxfoundation.org> In-Reply-To: <20150410131707.794709951@linuxfoundation.org> References: <20150410131707.794709951@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: "Michael S. Tsirkin" 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 Signed-off-by: Michael S. Tsirkin Tested-by: Thomas Huth Reviewed-by: Cornelia Huck Signed-off-by: Rusty Russell Signed-off-by: Greg Kroah-Hartman --- 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 #include #include +#include /* * 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)