On Thu, Feb 1, 2024 at 5:30 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > From: Yu Kuai <yukuai3@xxxxxxxxxx> > > mddev_suspend() never stop sync_thread, hence it doesn't make sense to > ignore suspended array in md_check_recovery(), which might cause > sync_thread can't be unregistered. > > After commit f52f5c71f3d4 ("md: fix stopping sync thread"), following > hang can be triggered by test shell/integrity-caching.sh: Hi Kuai After applying this patch, it's still stuck at mddev_suspend. Maybe the deadlock can be fixed by other patches from the patch set. But this patch can't fix this issue. If so, the comment is not right. > > 1) suspend the array: > raid_postsuspend > mddev_suspend > > 2) stop the array: > raid_dtr > md_stop > __md_stop_writes > stop_sync_thread > set_bit(MD_RECOVERY_INTR, &mddev->recovery); > md_wakeup_thread_directly(mddev->sync_thread); > wait_event(..., !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) > > 3) sync thread done: > md_do_sync > set_bit(MD_RECOVERY_DONE, &mddev->recovery); > md_wakeup_thread(mddev->thread); > > 4) daemon thread can't unregister sync thread: > md_check_recovery > if (mddev->suspended) > return; -> return directly > md_read_sync_thread > clear_bit(MD_RECOVERY_RUNNING, &mddev->recovery); > -> MD_RECOVERY_RUNNING can't be cleared, hence step 2 hang; I add some debug logs when stopping dmraid with lvremove command. The step you mentioned are sequential but not async. The process is : dev_remove->dm_destroy->__dm_destroy->dm_table_postsuspend_targets(raid_postsuspend) -> dm_table_destroy(raid_dtr). It looks like mddev_suspend is waiting for active_io to be zero. Best Regards Xiao > This problem is not just related to dm-raid, fix it by ignoring > suspended array in md_check_recovery(). And follow up patches will > improve dm-raid better to frozen sync thread during suspend. > > Reported-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Closes: https://lore.kernel.org/all/8fb335e-6d2c-dbb5-d7-ded8db5145a@xxxxxxxxxx/ > Fixes: 68866e425be2 ("MD: no sync IO while suspended") > Fixes: f52f5c71f3d4 ("md: fix stopping sync thread") > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> > --- > drivers/md/md.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/drivers/md/md.c b/drivers/md/md.c > index 2266358d8074..07b80278eaa5 100644 > --- a/drivers/md/md.c > +++ b/drivers/md/md.c > @@ -9469,9 +9469,6 @@ static void md_start_sync(struct work_struct *ws) > */ > void md_check_recovery(struct mddev *mddev) > { > - if (READ_ONCE(mddev->suspended)) > - return; > - > if (mddev->bitmap) > md_bitmap_daemon_work(mddev); > > -- > 2.39.2 >