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
>
