linux-kernel - [PATCH 3/3] hrtimer: fix the __hrtimer_start_range_ns() race with hrtimer

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Date:	Mon, 8 Jun 2015 17:11:56 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	umgwanakikbuti@...il.com, mingo@...e.hu, ktkhai@...allels.com,
	rostedt@...dmis.org, tglx@...utronix.de, juri.lelli@...il.com,
	pang.xunlei@...aro.org, wanpeng.li@...ux.intel.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] hrtimer: fix the __hrtimer_start_range_ns() race with
	hrtimer_active()

Change __hrtimer_start_range_ns() to preserve ENQUEUED.
---
 kernel/time/hrtimer.c |   10 +++++-----
 1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 5fceb3d..1761f96 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -902,8 +902,8 @@ out:
 /*
  * remove hrtimer, called with base lock held
  */
-static inline int
-remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
+static inline int remove_hrtimer(struct hrtimer *timer,
+			struct hrtimer_clock_base *base, bool clear_enqueued)
 {
 	if (hrtimer_is_queued(timer)) {
 		int reprogram;
@@ -923,7 +923,7 @@ remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
 		 * This preserves the CALLBACK flag,  otherwise we could move
 		 * the timer base in switch_hrtimer_base.
 		 */
-		__remove_hrtimer(timer, base, true, reprogram);
+		__remove_hrtimer(timer, base, clear_enqueued, reprogram);
 		return 1;
 	}
 	return 0;
@@ -940,7 +940,7 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 	base = lock_hrtimer_base(timer, &flags);
 
 	/* Remove an active timer from the queue: */
-	ret = remove_hrtimer(timer, base);
+	ret = remove_hrtimer(timer, base, false);
 
 	if (mode & HRTIMER_MODE_REL) {
 		tim = ktime_add_safe(tim, base->get_time());
@@ -1061,7 +1061,7 @@ int hrtimer_try_to_cancel(struct hrtimer *timer)
 	base = lock_hrtimer_base(timer, &flags);
 
 	if (!hrtimer_callback_running(timer))
-		ret = remove_hrtimer(timer, base);
+		ret = remove_hrtimer(timer, base, true);
 
 	unlock_hrtimer_base(timer, &flags);
 
-- 
1.5.5.1


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