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Date: Thu, 18 Aug 2016 16:14:04 +0200
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
Message-ID: <20160818141404.GA10121@twins.programming.kicks-ass.net>
References: <1470854648.17361.9.camel@j-VirtualBox>
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On Wed, Aug 10, 2016 at 11:44:08AM -0700, Jason Low wrote:
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 2cb7531..5643a233 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -57,6 +57,8 @@ struct mutex {
>  #endif
>  #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
>  	struct optimistic_spin_queue osq; /* Spinner MCS lock */
> +#elif defined(CONFIG_SMP)
> +	bool yield_to_waiter; /* Prevent starvation when spinning disabled */
>  #endif
>  #ifdef CONFIG_DEBUG_MUTEXES
>  	void			*magic;

Isn't this also possible on !SMP && PREEMPT ?