mm: fix lost kswapd wakeup in kswapd_stop()
Offlining memory may block forever, waiting for kswapd() to wake up because kswapd() does not check the event kthread->should_stop before sleeping. The proper pattern, from Documentation/memory-barriers.txt, is: --- waker --- event_indicated = 1; wake_up_process(event_daemon); --- sleeper --- for (;;) { set_current_state(TASK_UNINTERRUPTIBLE); if (event_indicated) break; schedule(); } set_current_state() may be wrapped by: prepare_to_wait(); In the kswapd() case, event_indicated is kthread->should_stop. === offlining memory (waker) === kswapd_stop() kthread_stop() kthread->should_stop = 1 wake_up_process() wait_for_completion() === kswapd_try_to_sleep (sleeper) === kswapd_try_to_sleep() prepare_to_wait() . . schedule() . . finish_wait() The schedule() needs to be protected by a test of kthread->should_stop, which is wrapped by kthread_should_stop(). Reproducer: Do heavy file I/O in background. Do a memory offline/online in a tight loop Signed-off-by: Aaditya Kumar <aaditya.kumar@ap.sony.com> Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Minchan Kim <minchan@kernel.org> Acked-by: Mel Gorman <mel@csn.ul.ie> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
parent
9a75c6e524
commit
1c7e7f6c07
|
@ -2688,7 +2688,10 @@ static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx)
|
|||
* them before going back to sleep.
|
||||
*/
|
||||
set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold);
|
||||
schedule();
|
||||
|
||||
if (!kthread_should_stop())
|
||||
schedule();
|
||||
|
||||
set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold);
|
||||
} else {
|
||||
if (remaining)
|
||||
|
|
Loading…
Reference in a new issue