From: Michal Hocko <mhocko@xxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/oom_kill.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff -puN mm/oom_kill.c~oom-oom_reaper-allow-to-reap-mm-shared-by-the-kthreads mm/oom_kill.c --- a/mm/oom_kill.c~oom-oom_reaper-allow-to-reap-mm-shared-by-the-kthreads +++ a/mm/oom_kill.c @@ -902,13 +902,7 @@ static void oom_kill_process(struct oom_ 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_ 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(); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
