From: John Pittman <jpittman@xxxxxxxxxx> [ Upstream commit 784c9a29e99eb40b842c29ecf1cc3a79e00fb629 ] It was reported that softlockups occur when using dm-snapshot ontop of slow (rbd) storage. E.g.: [ 4047.990647] watchdog: BUG: soft lockup - CPU#10 stuck for 22s! [kworker/10:23:26177] ... [ 4048.034151] Workqueue: kcopyd do_work [dm_mod] [ 4048.034156] RIP: 0010:copy_callback+0x41/0x160 [dm_snapshot] ... [ 4048.034190] Call Trace: [ 4048.034196] ? __chunk_is_tracked+0x70/0x70 [dm_snapshot] [ 4048.034200] run_complete_job+0x5f/0xb0 [dm_mod] [ 4048.034205] process_jobs+0x91/0x220 [dm_mod] [ 4048.034210] ? kcopyd_put_pages+0x40/0x40 [dm_mod] [ 4048.034214] do_work+0x46/0xa0 [dm_mod] [ 4048.034219] process_one_work+0x171/0x370 [ 4048.034221] worker_thread+0x1fc/0x3f0 [ 4048.034224] kthread+0xf8/0x130 [ 4048.034226] ? max_active_store+0x80/0x80 [ 4048.034227] ? kthread_bind+0x10/0x10 [ 4048.034231] ret_from_fork+0x35/0x40 [ 4048.034233] Kernel panic - not syncing: softlockup: hung tasks Fix this by calling cond_resched() after run_complete_job()'s callout to the dm_kcopyd_notify_fn (which is dm-snap.c:copy_callback in the above trace). Signed-off-by: John Pittman <jpittman@xxxxxxxxxx> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- drivers/md/dm-kcopyd.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c index cf2c67e35eaf..d4b326914f06 100644 --- a/drivers/md/dm-kcopyd.c +++ b/drivers/md/dm-kcopyd.c @@ -484,6 +484,8 @@ static int run_complete_job(struct kcopyd_job *job) if (atomic_dec_and_test(&kc->nr_jobs)) wake_up(&kc->destroyq); + cond_resched(); + return 0; } -- 2.17.1
