diff options
| author | Aaditya Kumar <aaditya.kumar.30@gmail.com> | 2012-07-17 15:48:07 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-08-01 12:26:54 -0700 |
| commit | 6d40de834ce9bb2964a70b7f91a98406eceb0399 (patch) | |
| tree | d82f496a2c3d125136c4c7d2eef5bceec7943964 /mm | |
| parent | dccecc646f06f06db8c32fc6615fee847852cec6 (diff) | |
mm: fix lost kswapd wakeup in kswapd_stop()
commit 1c7e7f6c0703d03af6bcd5ccc11fc15d23e5ecbe upstream.
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/vmscan.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c index 1b0ed361e5bf..130fa32441c0 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2695,7 +2695,10 @@ 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) |