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From: Peter Zijlstra <peterz@infradead.org>
To: Davidlohr Bueso <davidlohr@hp.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	Aswin Chandramouleeswaran <aswin@hp.com>,
	linux-kernel@vger.kernel.org, vgupta@synopsys.com
Subject: Re: [PATCH] arch,locking: Ciao arch_mutex_cpu_relax()
Date: Mon, 23 Jun 2014 08:54:23 +0200	[thread overview]
Message-ID: <20140623065423.GE19860@laptop.programming.kicks-ass.net> (raw)
In-Reply-To: <1403288473.10903.2.camel@buesod1.americas.hpqcorp.net>

On Fri, Jun 20, 2014 at 11:21:13AM -0700, Davidlohr Bueso wrote:
> diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
> index d99f9b3..8e1bf6b 100644
> --- a/arch/arc/include/asm/processor.h
> +++ b/arch/arc/include/asm/processor.h
> @@ -62,6 +62,8 @@ unsigned long thread_saved_pc(struct task_struct *t);
>  #define cpu_relax()	do { } while (0)
>  #endif
>  
> +#define arch_cpu_relax() cpu_relax()
> +
>  #define copy_segments(tsk, mm)      do { } while (0)
>  #define release_segments(mm)        do { } while (0)

I'm not at all sure that cpu_relax() definition ARC has is valid. We
rely on cpu_relax() being at least a barrier() all over the place, and
it doesn't need to be SMP only. You can have a UP wait loop waiting for
an interrupt for example.

Vineet?

  reply	other threads:[~2014-06-23  6:54 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-06-20 18:21 [PATCH] arch,locking: Ciao arch_mutex_cpu_relax() Davidlohr Bueso
2014-06-23  6:54 ` Peter Zijlstra [this message]
2014-06-23  7:13   ` Vineet Gupta
2014-06-23 11:34     ` Peter Zijlstra
2014-06-23  6:58 ` Peter Zijlstra
2014-06-24 15:06   ` Davidlohr Bueso
2014-06-25  6:25     ` Heiko Carstens
2014-06-25 11:57       ` Linus Torvalds
2014-06-29 22:09         ` [PATCH v2] " Davidlohr Bueso
2014-08-05 13:04           ` Geert Uytterhoeven
2014-08-05 17:42             ` Davidlohr Bueso
2014-08-08  1:18               ` Davidlohr Bueso
2014-08-08 10:45                 ` Guenter Roeck
2014-08-15 19:34                 ` Guenter Roeck

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