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authorMichal Hocko <mhocko@suse.com>2016-07-29 01:45:01 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-29 02:07:41 +0300
commita373966d1f64c04ba9d0159087f0fa1b5aac4c33 (patch)
treef02c2b0c78033061b0edea6c8cb7ed715dc0689d /mm/oom_kill.c
parent11a410d516e89320fe0817606eeab58f36c22968 (diff)
downloadlinux-a373966d1f64c04ba9d0159087f0fa1b5aac4c33.tar.xz
mm, oom: hide mm which is shared with kthread or global init
The only case where the oom_reaper is not triggered for the oom victim is when it shares the memory with a kernel thread (aka use_mm) or with the global init. After "mm, oom: skip vforked tasks from being selected" the victim cannot be a vforked task of the global init so we are left with clone(CLONE_VM) (without CLONE_SIGHAND). use_mm() users are quite rare as well. In order to help forward progress for the OOM killer, make sure that this really rare case will not get in the way - we do this by hiding the mm from the oom killer by setting MMF_OOM_REAPED flag for it. oom_scan_process_thread will ignore any TIF_MEMDIE task if it has MMF_OOM_REAPED flag set to catch these oom victims. After this patch we should guarantee forward progress for the OOM killer even when the selected victim is sharing memory with a kernel thread or global init as long as the victims mm is still alive. Link: http://lkml.kernel.org/r/1466426628-15074-11-git-send-email-mhocko@kernel.org Signed-off-by: Michal Hocko <mhocko@suse.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: Vladimir Davydov <vdavydov@virtuozzo.com> Cc: David Rientjes <rientjes@google.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/oom_kill.c')
-rw-r--r--mm/oom_kill.c25
1 files changed, 21 insertions, 4 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index bfddc93ccd34..4c21f744daa6 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -283,10 +283,22 @@ enum oom_scan_t oom_scan_process_thread(struct oom_control *oc,
/*
* This task already has access to memory reserves and is being killed.
- * Don't allow any other task to have access to the reserves.
+ * Don't allow any other task to have access to the reserves unless
+ * the task has MMF_OOM_REAPED because chances that it would release
+ * any memory is quite low.
*/
- if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims))
- return OOM_SCAN_ABORT;
+ if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims)) {
+ struct task_struct *p = find_lock_task_mm(task);
+ enum oom_scan_t ret = OOM_SCAN_ABORT;
+
+ if (p) {
+ if (test_bit(MMF_OOM_REAPED, &p->mm->flags))
+ ret = OOM_SCAN_CONTINUE;
+ task_unlock(p);
+ }
+
+ return ret;
+ }
/*
* If task is allocating a lot of memory and has been marked to be
@@ -913,9 +925,14 @@ void oom_kill_process(struct oom_control *oc, struct task_struct *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.
+ * memory might be still used. Hide the mm from the oom
+ * killer to guarantee OOM forward progress.
*/
can_oom_reap = false;
+ set_bit(MMF_OOM_REAPED, &mm->flags);
+ pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
+ task_pid_nr(victim), victim->comm,
+ task_pid_nr(p), p->comm);
continue;
}
do_send_sig_info(SIGKILL, SEND_SIG_FORCED, p, true);