From 8a32c441c1609f80e55df75422324a1151208f40 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 21 Nov 2011 12:32:23 -0800 Subject: freezer: implement and use kthread_freezable_should_stop() Writeback and thinkpad_acpi have been using thaw_process() to prevent deadlock between the freezer and kthread_stop(); unfortunately, this is inherently racy - nothing prevents freezing from happening between thaw_process() and kthread_stop(). This patch implements kthread_freezable_should_stop() which enters refrigerator if necessary but is guaranteed to return if kthread_stop() is invoked. Both thaw_process() users are converted to use the new function. Note that this deadlock condition exists for many of freezable kthreads. They need to be converted to use the new should_stop or freezable workqueue. Tested with synthetic test case. Signed-off-by: Tejun Heo Acked-by: Henrique de Moraes Holschuh Cc: Jens Axboe Cc: Oleg Nesterov --- include/linux/kthread.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/kthread.h') diff --git a/include/linux/kthread.h b/include/linux/kthread.h index 5cac19b3a266..0714b24c0e45 100644 --- a/include/linux/kthread.h +++ b/include/linux/kthread.h @@ -35,6 +35,7 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data), void kthread_bind(struct task_struct *k, unsigned int cpu); int kthread_stop(struct task_struct *k); int kthread_should_stop(void); +bool kthread_freezable_should_stop(bool *was_frozen); void *kthread_data(struct task_struct *k); int kthreadd(void *unused); -- cgit v1.2.1