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From: Peter Zijlstra <peterz@infradead.org>
To: Jason Low <jason.low2@hpe.com>
Cc: Ingo Molnar <mingo@redhat.com>,
	imre.deak@intel.com, linux-kernel@vger.kernel.org,
	Jason Low <jason.low2@hp.com>, Waiman Long <Waiman.Long@hpe.com>,
	Davidlohr Bueso <dave@stgolabs.net>,
	Tim Chen <tim.c.chen@linux.intel.com>,
	terry.rudd@hpe.com, "Paul E. McKenney" <paulmck@us.ibm.com>
Subject: Re: [PATCH v2] locking/mutex: Prevent lock starvation when spinning is enabled
Date: Thu, 18 Aug 2016 16:27:35 +0200	[thread overview]
Message-ID: <20160818142735.GB10121@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1470854648.17361.9.camel@j-VirtualBox>

On Wed, Aug 10, 2016 at 11:44:08AM -0700, Jason Low wrote:
> @@ -556,8 +604,12 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
>  		 * other waiters. We only attempt the xchg if the count is
>  		 * non-negative in order to avoid unnecessary xchg operations:
>  		 */
> -		if (atomic_read(&lock->count) >= 0 &&
> +		if ((!need_yield_to_waiter(lock) || wakeups > 1) &&
> +		    atomic_read(&lock->count) >= 0 &&
>  		    (atomic_xchg_acquire(&lock->count, -1) == 1))
> +			if (wakeups > 1)
> +				clear_yield_to_waiter(lock);
> +
>  			break;
>  
>  		/*

There's some { } gone missing there...

Also, I think I'll change it to avoid that extra wakeups > 1 condition..

  parent reply	other threads:[~2016-08-18 14:27 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-08-10 18:44 Jason Low
2016-08-10 20:00 ` kbuild test robot
2016-08-10 20:01 ` kbuild test robot
2016-08-16 20:19   ` Jason Low
2016-08-10 22:07 ` Jason Low
2016-08-11  2:30 ` Jason Low
2016-08-11 15:40 ` Waiman Long
2016-08-16 19:44   ` Jason Low
2016-08-17  1:41 ` Wanpeng Li
2016-08-17 18:30   ` Jason Low
2016-08-18  0:38     ` Wanpeng Li
2016-08-18 14:14 ` Peter Zijlstra
2016-08-18 15:22   ` Waiman Long
2016-08-18 14:27 ` Peter Zijlstra [this message]
2016-08-18 15:18   ` Peter Zijlstra
2016-08-18 15:30     ` Peter Zijlstra

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