On Wed, Jun 14, 2023 at 3:38 PM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > > Hi, > > 在 2023/06/14 15:12, Xiao Ni 写道: > > On Wed, Jun 14, 2023 at 10:04 AM Yu Kuai <yukuai1@xxxxxxxxxxxxxxx> wrote: > >> > >> Hi, > >> > >> 在 2023/06/14 9:48, Yu Kuai 写道: > >> > >> > >>>> > >>>> In the patch, sync_seq is added in md_reap_sync_thread. In > >>>> idle_sync_thread, if sync_seq isn't equal > >>>> > >>>> mddev->sync_seq, it should mean there is someone that stops the sync > >>>> thread already, right? Why do > >>>> > >>>> you say 'new started sync thread' here? > >> > >> If someone stops the sync thread, and new sync thread is not started, > >> then this sync_seq won't make a difference, above wait_event() will not > >> wait because !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) will pass. > >> So 'sync_seq' is only used when the old sync thread stops and new sync > >> thread starts, add 'sync_seq' will bypass this case. > > > > Hi > > > > If a new sync thread starts, why can sync_seq be different? sync_seq > > is only added in md_reap_sync_thread. And when a new sync request > > starts, it can't stop the sync request again? > > > > Af first, the sync_seq is 0 > > > > admin1 > > echo idle > sync_action > > idle_sync_thread(sync_seq is 1) > > Wait, I'm confused here, how can sync_seq to be 1 here? I suppose you > mean that there is a sync_thread just finished? Hi Kuai Yes. Because idle_sync_thread needs to wait until md_reap_sync_thread finishes. And md_reap_sync_thread adds sync_seq. Do I understand your patch right? > > Then the problem is that idle_sync_thread() read sync_seq after the old > sync_thread is done, and new sync_thread start before wait_event() is > called, should we wait for this new sync_thread? > > My answer here is that we should, but I'm also ok to not wait this new > sync_thread, I don't think this behaviour matters. The key point here > is that once wait_event() is called from idle_sync_thread(), this > wait_event() should not wait for new sync_thread... I think we should wait. If we don't wait for it, there is a problem. One person echos idle to sync_action and it doesn't work sometimes. It's a strange thing. > > > echo resync > sync_action (new sync) > > If this is behind "echo idle > sync_action", idle_sync_thread should not > see that MD_RECOVERY_RUNNING is set and wait_event() won't wait at all. `echo resync > sync_action` can't change the sync_seq. So 'echo idle > sync_action' still waits until MD_RECOVERY_RUNNING is cleared? Regards Xiao > > Thanks, > Kuai > > > > Then admin2 echos idle > sync_action, sync_seq is still 1 > > > > Regards > > Xiao > > > >> > >> Thanks, > >> Kuai > >> > > > > . > > > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
