From fada94ee64e6e18793b1db60fb8278d2eddbf922 Mon Sep 17 00:00:00 2001 From: Li Zhong Date: Fri, 14 Feb 2014 10:52:57 +0800 Subject: [PATCH 1/2] workqueue: add args to workqueue lockdep name Tommi noticed a 'funny' lock class name: "%s#5" from a lock acquired in process_one_work(). Maybe #fmt plus #args could be used as the lock_name to give some more information for some fmt string like the above. __builtin_constant_p() check is removed (as there seems no good way to check all the variables in args list). However, by removing the check, it only adds two additional "s for those constants. Some lockdep name examples printed out after the change: lockdep name wq->name "events_long" events_long "%s"("khelper") khelper "xfs-data/%s"mp->m_fsname xfs-data/dm-3 Signed-off-by: Li Zhong Signed-off-by: Tejun Heo --- include/linux/workqueue.h | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 594521ba0d43..704f4f652d0a 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -419,10 +419,7 @@ __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active, static struct lock_class_key __key; \ const char *__lock_name; \ \ - if (__builtin_constant_p(fmt)) \ - __lock_name = (fmt); \ - else \ - __lock_name = #fmt; \ + __lock_name = #fmt#args; \ \ __alloc_workqueue_key((fmt), (flags), (max_active), \ &__key, __lock_name, ##args); \ From 5bdfff96c69a4d5ab9c49e60abf9e070ecd2acbb Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Sat, 15 Feb 2014 22:02:28 +0800 Subject: [PATCH 2/2] workqueue: ensure @task is valid across kthread_stop() 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. CC: stable@vger.kernel.org Signed-off-by: Lai Jiangshan Signed-off-by: Tejun Heo --- kernel/workqueue.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 82ef9f3b7473..193e977a10ea 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -1851,6 +1851,12 @@ 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; @@ -1859,6 +1865,7 @@ static void destroy_worker(struct worker *worker) spin_unlock_irq(&pool->lock); kthread_stop(worker->task); + put_task_struct(worker->task); kfree(worker); spin_lock_irq(&pool->lock);