linux-kernel - [tip:sched/core] sched/core: Fix rq lock pinning warning after call balance callbacks

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Date:   Thu, 23 Mar 2017 02:11:57 -0700
From:   tip-bot for Wanpeng Li <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, wanpeng.li@...mail.com, hpa@...or.com,
        peterz@...radead.org, fengguang.wu@...el.com,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        torvalds@...ux-foundation.org, efault@....de
Subject: [tip:sched/core] sched/core: Fix rq lock pinning warning after call
 balance callbacks

Commit-ID:  d7921a5ddab8d30e06e321f37eec629f23797486
Gitweb:     http://git.kernel.org/tip/d7921a5ddab8d30e06e321f37eec629f23797486
Author:     Wanpeng Li <wanpeng.li@...mail.com>
AuthorDate: Thu, 16 Mar 2017 19:45:19 -0700
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 23 Mar 2017 07:44:51 +0100

sched/core: Fix rq lock pinning warning after call balance callbacks

This can be reproduced by running rt-migrate-test:

 WARNING: CPU: 2 PID: 2195 at kernel/locking/lockdep.c:3670 lock_unpin_lock()
 unpinning an unpinned lock
 ...
 Call Trace:
  dump_stack()
  __warn()
  warn_slowpath_fmt()
  lock_unpin_lock()
  __balance_callback()
  __schedule()
  schedule()
  futex_wait_queue_me()
  futex_wait()
  do_futex()
  SyS_futex()
  do_syscall_64()
  entry_SYSCALL64_slow_path()

Revert the rq_lock_irqsave() usage here, the whole point of the
balance_callback() was to allow dropping rq->lock.

Reported-by: Fengguang Wu <fengguang.wu@...el.com>
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Fixes: 8a8c69c32778 ("sched/core: Add rq->lock wrappers")
Link: http://lkml.kernel.org/r/1489718719-3951-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c762f62..ab9f6ac 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2776,9 +2776,9 @@ static void __balance_callback(struct rq *rq)
 {
 	struct callback_head *head, *next;
 	void (*func)(struct rq *rq);
-	struct rq_flags rf;
+	unsigned long flags;
 
-	rq_lock_irqsave(rq, &rf);
+	raw_spin_lock_irqsave(&rq->lock, flags);
 	head = rq->balance_callback;
 	rq->balance_callback = NULL;
 	while (head) {
@@ -2789,7 +2789,7 @@ static void __balance_callback(struct rq *rq)
 
 		func(rq);
 	}
-	rq_unlock_irqrestore(rq, &rf);
+	raw_spin_unlock_irqrestore(&rq->lock, flags);
 }
 
 static inline void balance_callback(struct rq *rq)