Commit e830c63a authored by Tetsuo Handa's avatar Tetsuo Handa Committed by Linus Torvalds

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: default avatarTetsuo Handa <>
Acked-by: default avatarMichal Hocko <>
Reviewed-by: default avatarAndrew Morton <>
Cc: Dave Chinner <>
Cc: Glauber Costa <>
Cc: Mel Gorman <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 5c9bab59
......@@ -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 = {
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