| Message ID | 1393421120-6681-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 89743ae..d19727f 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1472,12 +1472,19 @@ static void destroy_worker(struct worker *worker) if (worker->flags & WORKER_IDLE) gcwq->nr_idle--; + /* + * Once WORKER_DIE is set, the kworker may destroy itself at any + * point. Pin to ensure the task stays until we're done with it. + */ + get_task_struct(worker->task); + list_del_init(&worker->entry); worker->flags |= WORKER_DIE; spin_unlock_irq(&gcwq->lock); kthread_stop(worker->task); + put_task_struct(worker->task); kfree(worker); spin_lock_irq(&gcwq->lock);
This is a note to let you know that I have just added a patch titled workqueue: ensure @task is valid across kthread_stop() to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ------ From eb349206b92e4b6697da4efd6aedfa1824803017 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan <laijs@cn.fujitsu.com> Date: Sat, 15 Feb 2014 22:02:28 +0800 Subject: workqueue: ensure @task is valid across kthread_stop() commit 5bdfff96c69a4d5ab9c49e60abf9e070ecd2acbb upstream. When a kworker should die, the kworkre is notified through WORKER_DIE flag instead of kthread_should_stop(). This, IIRC, is primarily to keep the test synchronized inside worker_pool lock. WORKER_DIE is first set while holding pool->lock, the lock is dropped and kthread_stop() is called. Unfortunately, this means that there's a slight chance that the target kworker may see WORKER_DIE before kthread_stop() finishes and exits and frees the target task before or during kthread_stop(). Fix it by pinning the target task before setting WORKER_DIE and putting it after kthread_stop() is done. tj: Improved patch description and comment. Moved pinning above WORKER_DIE for better signify what it's protecting. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org> [ luis: backported to 3.5: adjusted context ] Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- kernel/workqueue.c | 7 +++++++ 1 file changed, 7 insertions(+) -- 1.9.0