1 files changed, 65 insertions, 46 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index e6c10640e56b..f8eba9651c0c 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -288,6 +288,59 @@ static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
 }
 #endif
 
+enum oom_scan_t {
+	OOM_SCAN_OK,		/* scan thread and find its badness */
+	OOM_SCAN_CONTINUE,	/* do not consider thread for oom kill */
+	OOM_SCAN_ABORT,		/* abort the iteration and return */
+	OOM_SCAN_SELECT,	/* always select this thread first */
+};
+
+static enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
+		struct mem_cgroup *memcg, unsigned long totalpages,
+		const nodemask_t *nodemask, bool force_kill)
+{
+	if (task->exit_state)
+		return OOM_SCAN_CONTINUE;
+	if (oom_unkillable_task(task, memcg, nodemask))
+		return OOM_SCAN_CONTINUE;
+
+	/*
+	 * This task already has access to memory reserves and is being killed.
+	 * Don't allow any other task to have access to the reserves.
+	 */
+	if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
+		if (unlikely(frozen(task)))
+			__thaw_task(task);
+		if (!force_kill)
+			return OOM_SCAN_ABORT;
+	}
+	if (!task->mm)
+		return OOM_SCAN_CONTINUE;
+
+	if (task->flags & PF_EXITING) {
+		/*
+		 * If task is current and is in the process of releasing memory,
+		 * allow the "kill" to set TIF_MEMDIE, which will allow it to
+		 * access memory reserves.  Otherwise, it may stall forever.
+		 *
+		 * The iteration isn't broken here, however, in case other
+		 * threads are found to have already been oom killed.
+		 */
+		if (task == current)
+			return OOM_SCAN_SELECT;
+		else if (!force_kill) {
+			/*
+			 * If this task is not being ptraced on exit, then wait
+			 * for it to finish before killing some other task
+			 * unnecessarily.
+			 */
+			if (!(task->group_leader->ptrace & PT_TRACE_EXIT))
+				return OOM_SCAN_ABORT;
+		}
+	}
+	return OOM_SCAN_OK;
+}
+
 /*
  * Simple selection loop. We chose the process with the highest
  * number of 'points'. We expect the caller will lock the tasklist.
@@ -305,53 +358,19 @@ static struct task_struct *select_bad_process(unsigned int *ppoints,
 	do_each_thread(g, p) {
 		unsigned int points;
 
-		if (p->exit_state)
-			continue;
-		if (oom_unkillable_task(p, memcg, nodemask))
-			continue;
-
-		/*
-		 * This task already has access to memory reserves and is
-		 * being killed. Don't allow any other task access to the
-		 * memory reserve.
-		 *
-		 * Note: this may have a chance of deadlock if it gets
-		 * blocked waiting for another task which itself is waiting
-		 * for memory. Is there a better alternative?
-		 */
-		if (test_tsk_thread_flag(p, TIF_MEMDIE)) {
-			if (unlikely(frozen(p)))
-				__thaw_task(p);
-			if (!force_kill)
-				return ERR_PTR(-1UL);
-		}
-		if (!p->mm)
+		switch (oom_scan_process_thread(p, memcg, totalpages, nodemask,
+						force_kill)) {
+		case OOM_SCAN_SELECT:
+			chosen = p;
+			chosen_points = ULONG_MAX;
+			/* fall through */
+		case OOM_SCAN_CONTINUE:
 			continue;
-
-		if (p->flags & PF_EXITING) {
-			/*
-			 * If p is the current task and is in the process of
-			 * releasing memory, we allow the "kill" to set
-			 * TIF_MEMDIE, which will allow it to gain access to
-			 * memory reserves.  Otherwise, it may stall forever.
-			 *
-			 * The loop isn't broken here, however, in case other
-			 * threads are found to have already been oom killed.
-			 */
-			if (p == current) {
-				chosen = p;
-				chosen_points = ULONG_MAX;
-			} else if (!force_kill) {
-				/*
-				 * If this task is not being ptraced on exit,
-				 * then wait for it to finish before killing
-				 * some other task unnecessarily.
-				 */
-				if (!(p->group_leader->ptrace & PT_TRACE_EXIT))
-					return ERR_PTR(-1UL);
-			}
-		}
-
+		case OOM_SCAN_ABORT:
+			return ERR_PTR(-1UL);
+		case OOM_SCAN_OK:
+			break;
+		};
 		points = oom_badness(p, memcg, nodemask, totalpages);
 		if (points > chosen_points) {
 			chosen = p;