3.10-stable review patch. If anyone has any objections, please let me know.
------------------ From: Lai Jiangshan <la...@cn.fujitsu.com> 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 <la...@cn.fujitsu.com> Signed-off-by: Tejun Heo <t...@kernel.org> Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org> --- kernel/workqueue.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1823,6 +1823,12 @@ static void destroy_worker(struct 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; @@ -1831,6 +1837,7 @@ static void destroy_worker(struct worker spin_unlock_irq(&pool->lock); kthread_stop(worker->task); + put_task_struct(worker->task); kfree(worker); spin_lock_irq(&pool->lock); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/