From: Tang Junhui <tang.junhui@xxxxxxxxxx>
LGTM.
Reviewed-by: Tang Junhui <tang.junhui@xxxxxxxxxx>
>Kernel thread routine bch_writeback_thread() has the following code block,
>
>452 set_current_state(TASK_INTERRUPTIBLE);
>453
>454 if (kthread_should_stop())
>455 return 0;
>456
>457 schedule();
>458 continue;
>
>At line 452, its status is set to TASK_INTERRUPTIBLE, and at line 454 if
>kthread_should_stop() is true, a "return 0" at line 455 will to function
>kernel/kthread.c:kthread() and call do_exit().
>
>It is not good to enter do_exit() with task state TASK_INTERRUPTIBLE, in
>following code path might_sleep() is called and a warning message is
>reported by __might_sleep(): "WARNING: do not call blocking ops when
>!TASK_RUNNING; state=1 set at [xxxx]".
>
>Indeed it does not hurt when kernel thread exits with TASK_INTERRUPTIBLE
>state, but this warning message scares users, makes them feel there might
>be something risky with bcache and hurt their data.
>
>In this patch, TASK_INTERRUPTIBLE is set after kthread_should_stop(),
>so writeback kernel thread can exist and enter do_exit() with
>TASK_RUNNING state. Warning message from might_sleep() is removed.
>
>Signed-off-by: Coly Li <colyli@xxxxxxx>
>---
> drivers/md/bcache/writeback.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
>index 56a37884ca8b..a57149803df6 100644
>--- a/drivers/md/bcache/writeback.c
>+++ b/drivers/md/bcache/writeback.c
>@@ -449,11 +449,11 @@ static int bch_writeback_thread(void *arg)
> (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
> !dc->writeback_running)) {
> up_write(&dc->writeback_lock);
>- set_current_state(TASK_INTERRUPTIBLE);
>
> if (kthread_should_stop())
> return 0;
>
>+ set_current_state(TASK_INTERRUPTIBLE);
> schedule();
> continue;
> }
>--
>2.15.1
Thanks,
Tang Junhui
