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From:   Cong Wang <xiyou.wangcong@gmail.com>
To:     linux-kernel@vger.kernel.org
Cc:     Cong Wang <xiyou.wangcong@gmail.com>,
        Xunlei Pang <xlpang@linux.alibaba.com>,
        Ben Segall <bsegall@google.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: [PATCH] sched/fair: sync expires_seq in distribute_cfs_runtime()
Date:   Fri, 27 Jul 2018 17:24:09 -0700
Message-Id: <20180728002409.5781-1-xiyou.wangcong@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Each time we sync cfs_rq->runtime_expires with cfs_b->runtime_expires,
we should sync its ->expires_seq too. However it is missing
for distribute_cfs_runtime(), especially the slack timer call path.

Fixes: 512ac999d275 ("sched/fair: Fix bandwidth timer clock drift condition")
Cc: Xunlei Pang <xlpang@linux.alibaba.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
 kernel/sched/fair.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2f0a0be4d344..910c50db3d74 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4857,7 +4857,7 @@ void unthrottle_cfs_rq(struct cfs_rq *cfs_rq)
 }
 
 static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
-		u64 remaining, u64 expires)
+		u64 remaining, u64 expires, int expires_seq)
 {
 	struct cfs_rq *cfs_rq;
 	u64 runtime;
@@ -4880,6 +4880,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
 
 		cfs_rq->runtime_remaining += runtime;
 		cfs_rq->runtime_expires = expires;
+		cfs_rq->expires_seq = expires_seq;
 
 		/* we check whether we're throttled above */
 		if (cfs_rq->runtime_remaining > 0)
@@ -4905,7 +4906,7 @@ static u64 distribute_cfs_runtime(struct cfs_bandwidth *cfs_b,
 static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
 {
 	u64 runtime, runtime_expires;
-	int throttled;
+	int throttled, expires_seq;
 
 	/* no need to continue the timer with no bandwidth constraint */
 	if (cfs_b->quota == RUNTIME_INF)
@@ -4933,6 +4934,7 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
 	cfs_b->nr_throttled += overrun;
 
 	runtime_expires = cfs_b->runtime_expires;
+	expires_seq = cfs_b->expires_seq;
 
 	/*
 	 * This check is repeated as we are holding onto the new bandwidth while
@@ -4946,7 +4948,7 @@ static int do_sched_cfs_period_timer(struct cfs_bandwidth *cfs_b, int overrun)
 		raw_spin_unlock(&cfs_b->lock);
 		/* we can't nest cfs_b->lock while distributing bandwidth */
 		runtime = distribute_cfs_runtime(cfs_b, runtime,
-						 runtime_expires);
+						 runtime_expires, expires_seq);
 		raw_spin_lock(&cfs_b->lock);
 
 		throttled = !list_empty(&cfs_b->throttled_cfs_rq);
@@ -5055,6 +5057,7 @@ static __always_inline void return_cfs_rq_runtime(struct cfs_rq *cfs_rq)
 static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
 {
 	u64 runtime = 0, slice = sched_cfs_bandwidth_slice();
+	int expires_seq;
 	u64 expires;
 
 	/* confirm we're still not at a refresh boundary */
@@ -5068,12 +5071,13 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
 		runtime = cfs_b->runtime;
 
 	expires = cfs_b->runtime_expires;
+	expires_seq = cfs_b->expires_seq;
 	raw_spin_unlock(&cfs_b->lock);
 
 	if (!runtime)
 		return;
 
-	runtime = distribute_cfs_runtime(cfs_b, runtime, expires);
+	runtime = distribute_cfs_runtime(cfs_b, runtime, expires, expires_seq);
 
 	raw_spin_lock(&cfs_b->lock);
 	if (expires == cfs_b->runtime_expires)
-- 
2.14.4