path: root/kernel/kthread.c
diff options
authorTejun Heo <tj@kernel.org>2011-11-21 12:32:23 -0800
committerTejun Heo <tj@kernel.org>2011-11-21 12:32:23 -0800
commit8a32c441c1609f80e55df75422324a1151208f40 (patch)
tree73884b06cc2db3ea155af9a88815bb5105a4473e /kernel/kthread.c
parenta0acae0e886d44bd5ce6d2f173c1ace0fcf0d9f6 (diff)
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 <tj@kernel.org> Acked-by: Henrique de Moraes Holschuh <ibm-acpi@hmh.eng.br> Cc: Jens Axboe <axboe@kernel.dk> Cc: Oleg Nesterov <oleg@redhat.com>
Diffstat (limited to 'kernel/kthread.c')
1 files changed, 25 insertions, 0 deletions
diff --git a/kernel/kthread.c b/kernel/kthread.c
index b6d216a9263..1c36deaae2f 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -59,6 +59,31 @@ int kthread_should_stop(void)
+ * kthread_freezable_should_stop - should this freezable kthread return now?
+ * @was_frozen: optional out parameter, indicates whether %current was frozen
+ *
+ * kthread_should_stop() for freezable kthreads, which will enter
+ * refrigerator if necessary. This function is safe from kthread_stop() /
+ * freezer deadlock and freezable kthreads should use this function instead
+ * of calling try_to_freeze() directly.
+ */
+bool kthread_freezable_should_stop(bool *was_frozen)
+ bool frozen = false;
+ might_sleep();
+ if (unlikely(freezing(current)))
+ frozen = __refrigerator(true);
+ if (was_frozen)
+ *was_frozen = frozen;
+ return kthread_should_stop();
* kthread_data - return data value specified on kthread creation
* @task: kthread task in question