From 1b51e65eab64fac72cab009691e8ca9915624876 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Fri, 7 Oct 2016 16:59:09 -0700 Subject: [PATCH] oom, oom_reaper: allow to reap mm shared by the kthreads oom reaper was skipped for an mm which is shared with the kernel thread (aka use_mm()). The primary concern was that such a kthread might want to read from the userspace memory and see zero page as a result of the oom reaper action. This is no longer a problem after "mm: make sure that kthreads will not refault oom reaped memory" because any attempt to fault in when the MMF_UNSTABLE is set will result in SIGBUS and so the target user should see an error. This means that we can finally allow oom reaper also to tasks which share their mm with kthreads. Link: http://lkml.kernel.org/r/1472119394-11342-10-git-send-email-mhocko@kernel.org Signed-off-by: Michal Hocko Cc: Tetsuo Handa Cc: Oleg Nesterov Cc: David Rientjes Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 5a3ba96c8338..10f686969fc4 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -902,13 +902,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message) continue; if (same_thread_group(p, victim)) continue; - if (unlikely(p->flags & PF_KTHREAD) || is_global_init(p)) { - /* - * We cannot use oom_reaper for the mm shared by this - * process because it wouldn't get killed and so the - * memory might be still used. Hide the mm from the oom - * killer to guarantee OOM forward progress. - */ + if (is_global_init(p)) { can_oom_reap = false; set_bit(MMF_OOM_SKIP, &mm->flags); pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n", @@ -916,6 +910,12 @@ static void oom_kill_process(struct oom_control *oc, const char *message) task_pid_nr(p), p->comm); continue; } + /* + * No use_mm() user needs to read from the userspace so we are + * ok to reap it. + */ + if (unlikely(p->flags & PF_KTHREAD)) + continue; do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true); } rcu_read_unlock(); -- 2.20.1