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Date: Thu, 8 May 2014 21:00:04 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <Waiman.Long@hp.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
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Subject: Re: [PATCH v10 07/19] qspinlock: Use a simple write to grab the
 lock, if applicable
Message-ID: <20140508190004.GO2844@laptop.programming.kicks-ass.net>
References: <1399474907-22206-1-git-send-email-Waiman.Long@hp.com>
 <1399474907-22206-8-git-send-email-Waiman.Long@hp.com>
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On Wed, May 07, 2014 at 11:01:35AM -0400, Waiman Long wrote:
> @@ -94,23 +94,29 @@ static inline struct mcs_spinlock *decode_tail(u32 tail)
>   * can allow better optimization of the lock acquisition for the pending
>   * bit holder.
>   */
> -#if _Q_PENDING_BITS == 8
> -
>  struct __qspinlock {
>  	union {
>  		atomic_t val;
> -		struct {
>  #ifdef __LITTLE_ENDIAN
> +		u8	 locked;
> +		struct {
>  			u16	locked_pending;
>  			u16	tail;
> +		};
>  #else
> +		struct {
>  			u16	tail;
>  			u16	locked_pending;
> -#endif
>  		};
> +		struct {
> +			u8	reserved[3];
> +			u8	locked;
> +		};
> +#endif
>  	};
>  };
>  
> +#if _Q_PENDING_BITS == 8

That doesn't make sense, that struct __qspinlock only makes sense when
_Q_PENDING_BITS == 8.