Merge tag 'leds_for_4.14' of git://git.kernel.org/pub/scm/linux/kernel/git/j.anaszews...

[sfrench/cifs-2.6.git] / mm / oom_kill.c

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 9e8b4f030c1c43cb92da706306e1b9390658af7b..99736e026712c42c73c676c5e1889f86d7d05d53 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -495,11 +495,12 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
        }
 
        /*
-        * increase mm_users only after we know we will reap something so
-        * that the mmput_async is called only when we have reaped something
-        * and delayed __mmput doesn't matter that much
+        * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
+        * work on the mm anymore. The check for MMF_OOM_SKIP must run
+        * under mmap_sem for reading because it serializes against the
+        * down_write();up_write() cycle in exit_mmap().
         */
-       if (!mmget_not_zero(mm)) {
+       if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
                up_read(&mm->mmap_sem);
                trace_skip_task_reaping(tsk->pid);
                goto unlock_oom;
@@ -542,12 +543,6 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
                        K(get_mm_counter(mm, MM_SHMEMPAGES)));
        up_read(&mm->mmap_sem);
 
-       /*
-        * Drop our reference but make sure the mmput slow path is called from a
-        * different context because we shouldn't risk we get stuck there and
-        * put the oom_reaper out of the way.
-        */
-       mmput_async(mm);
        trace_finish_task_reaping(tsk->pid);
 unlock_oom:
        mutex_unlock(&oom_lock);
@@ -824,7 +819,8 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
 
        /*
         * If the task is already exiting, don't alarm the sysadmin or kill
-        * its children or threads, just set TIF_MEMDIE so it can die quickly
+        * its children or threads, just give it access to memory reserves
+        * so it can die quickly
         */
        task_lock(p);
        if (task_will_free_mem(p)) {
@@ -889,9 +885,9 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
        count_memcg_event_mm(mm, OOM_KILL);
 
        /*
-        * We should send SIGKILL before setting TIF_MEMDIE in order to prevent
-        * the OOM victim from depleting the memory reserves from the user
-        * space under its control.
+        * We should send SIGKILL before granting access to memory reserves
+        * in order to prevent the OOM victim from depleting the memory
+        * reserves from the user space under its control.
         */
        do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
        mark_oom_victim(victim);