On Mon, 2020-09-21 at 18:12 +0200, Greg KH wrote: > On Thu, Sep 17, 2020 at 06:19:13PM -0700, Julius Hemanth Pitti wrote: > > From: Xunlei Pang <xlpang@xxxxxxxxxxxxxxxxx> > > > > commit e3336cab2579012b1e72b5265adf98e2d6e244ad upstream. > > > > We've met softlockup with "CONFIG_PREEMPT_NONE=y", when the target > > memcg > > doesn't have any reclaimable memory. > > > > It can be easily reproduced as below: > > > > watchdog: BUG: soft lockup - CPU#0 stuck for > > 111s![memcg_test:2204] > > CPU: 0 PID: 2204 Comm: memcg_test Not tainted 5.9.0-rc2+ #12 > > Call Trace: > > shrink_lruvec+0x49f/0x640 > > shrink_node+0x2a6/0x6f0 > > do_try_to_free_pages+0xe9/0x3e0 > > try_to_free_mem_cgroup_pages+0xef/0x1f0 > > try_charge+0x2c1/0x750 > > mem_cgroup_charge+0xd7/0x240 > > __add_to_page_cache_locked+0x2fd/0x370 > > add_to_page_cache_lru+0x4a/0xc0 > > pagecache_get_page+0x10b/0x2f0 > > filemap_fault+0x661/0xad0 > > ext4_filemap_fault+0x2c/0x40 > > __do_fault+0x4d/0xf9 > > handle_mm_fault+0x1080/0x1790 > > > > It only happens on our 1-vcpu instances, because there's no chance > > for > > oom reaper to run to reclaim the to-be-killed process. > > > > Add a cond_resched() at the upper shrink_node_memcgs() to solve > > this > > issue, this will mean that we will get a scheduling point for each > > memcg > > in the reclaimed hierarchy without any dependency on the > > reclaimable > > memory in that memcg thus making it more predictable. > > > > Suggested-by: Michal Hocko <mhocko@xxxxxxxx> > > Signed-off-by: Xunlei Pang <xlpang@xxxxxxxxxxxxxxxxx> > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > Acked-by: Chris Down <chris@xxxxxxxxxxxxxx> > > Acked-by: Michal Hocko <mhocko@xxxxxxxx> > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx> > > Link: > > http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@xxxxxxxxxxxxxxxxx > > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > > Fixes: b0dedc49a2da ("mm/vmscan.c: iterate only over charged > > shrinkers during memcg shrink_slab()") > > Cc: stable@xxxxxxxxxxxxxxx > > Signed-off-by: Julius Hemanth Pitti <jpitti@xxxxxxxxx> > > --- > > mm/vmscan.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > The Fixes: tag you show here goes back to 4.19, can you provide a > 4.19.y > and 5.4.y version of this as well? Sure. Will send for both 5.4.y and 4.19.y. > > thanks, > > greg k-h
