From d7a94e7e11badf8404d40b41e008c3131a3cebe3 Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Wed, 11 Feb 2015 15:24:54 -0800 Subject: [PATCH] oom: don't count on mm-less current process out_of_memory() doesn't trigger the OOM killer if the current task is already exiting or it has fatal signals pending, and gives the task access to memory reserves instead. However, doing so is wrong if out_of_memory() is called by an allocation (e.g. from exit_task_work()) after the current task has already released its memory and cleared TIF_MEMDIE at exit_mm(). If we again set TIF_MEMDIE to post-exit_mm() current task, the OOM killer will be blocked by the task sitting in the final schedule() waiting for its parent to reap it. It will trigger an OOM livelock if its parent is unable to reap it due to doing an allocation and waiting for the OOM killer to kill it. Signed-off-by: Tetsuo Handa Acked-by: Michal Hocko Cc: David Rientjes Cc: Oleg Nesterov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/oom_kill.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index d503e9ce1c7b..f82dd13cca68 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -643,8 +643,12 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask, * If current has a pending SIGKILL or is exiting, then automatically * select it. The goal is to allow it to allocate so that it may * quickly exit and free its memory. + * + * But don't select if current has already released its mm and cleared + * TIF_MEMDIE flag at exit_mm(), otherwise an OOM livelock may occur. */ - if (fatal_signal_pending(current) || task_will_free_mem(current)) { + if (current->mm && + (fatal_signal_pending(current) || task_will_free_mem(current))) { set_thread_flag(TIF_MEMDIE); return; } -- GitLab