From e830c63a621e20894a663351b968706bd0efbbd0 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Thu, 5 Apr 2018 16:23:35 -0700 Subject: [PATCH] mm,vmscan: don't pretend forward progress upon shrinker_rwsem contention Since we no longer use return value of shrink_slab() for normal reclaim, the comment is no longer true. If some do_shrink_slab() call takes unexpectedly long (root cause of stall is currently unknown) when register_shrinker()/unregister_shrinker() is pending, trying to drop caches via /proc/sys/vm/drop_caches could become infinite cond_resched() loop if many mem_cgroup are defined. For safety, let's not pretend forward progress. Link: http://lkml.kernel.org/r/201802202229.GGF26507.LVFtMSOOHFJOQF@I-love.SAKURA.ne.jp Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Reviewed-by: Andrew Morton Cc: Dave Chinner Cc: Glauber Costa Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/vmscan.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index ca566640c448..976be140a8ce 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -442,16 +442,8 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, if (memcg && (!memcg_kmem_enabled() || !mem_cgroup_online(memcg))) return 0; - if (!down_read_trylock(&shrinker_rwsem)) { - /* - * If we would return 0, our callers would understand that we - * have nothing else to shrink and give up trying. By returning - * 1 we keep it going and assume we'll be able to shrink next - * time. - */ - freed = 1; + if (!down_read_trylock(&shrinker_rwsem)) goto out; - } list_for_each_entry(shrinker, &shrinker_list, list) { struct shrink_control sc = {