Messages in this thread Patch in this message | | | From | Tetsuo Handa <> | Subject | [PATCH v2] mm,oom: don't abort on exiting processes when selecting a victim. | Date | Wed, 17 Feb 2016 23:31:25 +0900 |
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Currently, oom_scan_process_thread() returns OOM_SCAN_ABORT when there is a thread which is exiting. But it is possible that that thread is blocked at down_read(&mm->mmap_sem) in exit_mm() called from do_exit() whereas one of threads sharing that memory is doing a GFP_KERNEL allocation between down_write(&mm->mmap_sem) and up_write(&mm->mmap_sem) (e.g. mmap()).
---------- T1 T2 Calls mmap() Calls _exit(0) Arrives at vm_mmap_pgoff() Arrives at do_exit() Gets PF_EXITING via exit_signals() Calls down_write(&mm->mmap_sem) Calls do_mmap_pgoff() Calls down_read(&mm->mmap_sem) from exit_mm() Calls out of memory via a GFP_KERNEL allocation but oom_scan_process_thread(T1) returns OOM_SCAN_ABORT ----------
down_read(&mm->mmap_sem) by T1 is waiting for up_write(&mm->mmap_sem) by T2 while oom_scan_process_thread() by T2 is waiting for T1 to set T1->mm = NULL. Under such situation, the OOM killer does not choose a victim, which results in silent OOM livelock problem.
This patch changes oom_scan_process_thread() not to return OOM_SCAN_ABORT when there is a thread which is exiting.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org> --- mm/oom_kill.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index cf87153..6e6abaf 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -292,9 +292,6 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc, if (oom_task_origin(task)) return OOM_SCAN_SELECT; - if (task_will_free_mem(task) && !is_sysrq_oom(oc)) - return OOM_SCAN_ABORT; - return OOM_SCAN_OK; } -- 1.8.3.1
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