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@linux.alibaba.com
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@suse.com Signed-off-by: Xunlei Pang xlpang@linux.alibaba.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Acked-by: Chris Down chris@chrisdown.name Acked-by: Michal Hocko mhocko@suse.com Acked-by: Johannes Weiner hannes@cmpxchg.org Link: http://lkml.kernel.org/r/1598495549-67324-1-git-send-email-xlpang@linux.alib... Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Fixes: b0dedc49a2da ("mm/vmscan.c: iterate only over charged shrinkers during memcg shrink_slab()") Cc: stable@vger.kernel.org Signed-off-by: Julius Hemanth Pitti jpitti@cisco.com
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