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authorHaifeng Xu <haifeng.xu@shopee.com>2023-04-19 06:07:39 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-06-10 02:25:16 +0300
commit18b1d18bc2bd8f54e8df6bc8096185361a6d1b15 (patch)
tree2cdaabb2f0eba3a96129dd66e4ee21fc424bcb91
parent857f21397f7113e4f764aa65fb0160eb7f404808 (diff)
downloadlinux-18b1d18bc2bd8f54e8df6bc8096185361a6d1b15.tar.xz
memcg, oom: remove explicit wakeup in mem_cgroup_oom_synchronize()
Before commit 29ef680ae7c2 ("memcg, oom: move out_of_memory back to the charge path"), all memcg oom killers were delayed to page fault path. And the explicit wakeup is used in this case: thread A: ... if (locked) { // complete oom-kill, hold the lock mem_cgroup_oom_unlock(memcg); ... } ... thread B: ... if (locked && !memcg->oom_kill_disable) { ... } else { schedule(); // can't acquire the lock ... } ... The reason is that thread A kicks off the OOM-killer, which leads to wakeups from the uncharges of the exiting task. But thread B is not guaranteed to see them if it enters the OOM path after the OOM kills but before thread A releases the lock. Now only oom_kill_disable case is handled from the #PF path. In that case it is userspace to trigger the wake up not the #PF path itself. All potential paths to free some charges are responsible to call memcg_oom_recover() , so the explicit wakeup is not needed in the mem_cgroup_oom_synchronize() path which doesn't release any memory itself. Link: https://lkml.kernel.org/r/20230419030739.115845-2-haifeng.xu@shopee.com Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com> Suggested-by: Michal Hocko <mhocko@suse.com> Acked-by: Michal Hocko <mhocko@suse.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Roman Gushchin <roman.gushchin@linux.dev> Cc: Shakeel Butt <shakeelb@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
-rw-r--r--mm/memcontrol.c9
1 files changed, 1 insertions, 8 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e8aead97454b..d31fb1e2cb33 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2028,15 +2028,8 @@ bool mem_cgroup_oom_synchronize(bool handle)
mem_cgroup_unmark_under_oom(memcg);
finish_wait(&memcg_oom_waitq, &owait.wait);
- if (locked) {
+ if (locked)
mem_cgroup_oom_unlock(memcg);
- /*
- * There is no guarantee that an OOM-lock contender
- * sees the wakeups triggered by the OOM kill
- * uncharges. Wake any sleepers explicitly.
- */
- memcg_oom_recover(memcg);
- }
cleanup:
current->memcg_in_oom = NULL;
css_put(&memcg->css);