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Date: Fri, 17 Jul 2015 12:15:35 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Will Deacon <will.deacon@arm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        "paulmck@linux.vnet.ibm.com" <paulmck@linux.vnet.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v2] memory-barriers: remove
 smp_mb__after_unlock_lock()
Message-ID: <20150717101535.GR3644@twins.programming.kicks-ass.net>
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On Fri, Jul 17, 2015 at 10:32:21AM +0100, Will Deacon wrote:
> @@ -158,9 +140,7 @@ void arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
>  
>  static inline void arch_spin_unlock(arch_spinlock_t *lock)
>  {
> -	SYNC_IO;
> -	__asm__ __volatile__("# arch_spin_unlock\n\t"
> -				PPC_RELEASE_BARRIER: : :"memory");
> +	smp_mb();
>  	lock->slock = 0;
>  }

Should we then also make smp_store_release() use sync instead of lwsync
to keep it consistent?