---

yaml
---
r: 217439
b: refs/heads/master
c: 1e99bad
h: refs/heads/master
i:
  217437: 851dc22
  217435: 7ec520e
  217431: 1695f48
  217423: 6afbc20
  217407: aec49a4
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e18641e19a9204f241f04a5ac700168dcd18de4f
+refs/heads/master: 1e99bad0d9c12a4aaa60cd812c84ef152564bcf5

trunk/mm/oom_kill.c

@@ -404,16 +404,40 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
 #define K(x) ((x) << (PAGE_SHIFT-10))
 static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
 {
+	struct task_struct *q;
+	struct mm_struct *mm;
+
 	p = find_lock_task_mm(p);
 	if (!p)
 		return 1;
 
+	/* mm cannot be safely dereferenced after task_unlock(p) */
+	mm = p->mm;
+
 	pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
 		task_pid_nr(p), p->comm, K(p->mm->total_vm),
 		K(get_mm_counter(p->mm, MM_ANONPAGES)),
 		K(get_mm_counter(p->mm, MM_FILEPAGES)));
 	task_unlock(p);
 
+	/*
+	 * Kill all processes sharing p->mm in other thread groups, if any.
+	 * They don't get access to memory reserves or a higher scheduler
+	 * priority, though, to avoid depletion of all memory or task
+	 * starvation.  This prevents mm->mmap_sem livelock when an oom killed
+	 * task cannot exit because it requires the semaphore and its contended
+	 * by another thread trying to allocate memory itself.  That thread will
+	 * now get access to memory reserves since it has a pending fatal
+	 * signal.
+	 */
+	for_each_process(q)
+		if (q->mm == mm && !same_thread_group(q, p)) {
+			task_lock(q);	/* Protect ->comm from prctl() */
+			pr_err("Kill process %d (%s) sharing same memory\n",
+				task_pid_nr(q), q->comm);
+			task_unlock(q);
+			force_sig(SIGKILL, q);
+		}
 
 	set_tsk_thread_flag(p, TIF_MEMDIE);
 	force_sig(SIGKILL, p);