| Message ID | 1395330881-6112-1-git-send-email-kamal@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 338b3bd..1fd7e24 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1902,12 +1902,19 @@ static void destroy_worker(struct worker *worker) if (worker->flags & WORKER_IDLE) pool->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-3.8.y-queue branch of the 3.8.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-3.8.y-queue This patch is scheduled to be released in version 3.8.13.20. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From f8b55448454670fd26c6102f282aa814b58e1f9c 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> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- kernel/workqueue.c | 7 +++++++ 1 file changed, 7 insertions(+) -- 1.8.3.2