On Tue, 2021-07-06 at 14:52 +0100, Luis Henriques wrote: > * changes since v3: > - always round the delay with round_jiffies_relative() in function > schedule_delayed() (patch 0001) > > This is an attempt to fix the softlock on the delayed_work workqueue. As > stated in 0002 patch: > > Function ceph_check_delayed_caps() is called from the mdsc->delayed_work > workqueue and it can be kept looping for quite some time if caps keep being > added back to the mdsc->cap_delay_list. This may result in the watchdog > tainting the kernel with the softlockup flag. > > v2 of this fix modifies the approach by time-bounding the loop in this > function, so that any caps added to the list *after* the loop starts will > be postponed to the next wq run. > > An extra change in 0001 (suggested by Jeff) allows scheduling runs for > periods smaller than the default (5 secs) period. This way, > delayed_work() can have the next run scheduled for the next list element > ci->i_hold_caps_max instead of 5 secs. > > This patchset should fix the issue reported here [1], although a quick > search for "ceph_check_delayed_caps" in the tracker returns a few more > bugs, possibly duplicates. > > [1] https://tracker.ceph.com/issues/46284 > > Luis Henriques (2): > ceph: allow schedule_delayed() callers to set delay for workqueue > ceph: reduce contention in ceph_check_delayed_caps() > > fs/ceph/caps.c | 17 ++++++++++++++++- > fs/ceph/mds_client.c | 25 ++++++++++++++++--------- > fs/ceph/super.h | 2 +- > 3 files changed, 33 insertions(+), 11 deletions(-) > FWIW, we've had some more reports of this, so I think we should get this into mainline and stable soon. I'm going to squash these two patches together as it should (hopefully) make it simpler for stable backports. Thanks, -- Jeff Layton <jlayton@xxxxxxxxxx>
