linux-kernel - Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning

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Message-ID: <alpine.LFD.2.00.0901071518570.3057@localhost.localdomain>
Date:	Wed, 7 Jan 2009 15:19:23 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	paulmck@...ux.vnet.ibm.com, Gregory Haskins <ghaskins@...ell.com>,
	Ingo Molnar <mingo@...e.hu>, Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>,
	Chris Mason <chris.mason@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>
Subject: Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning



On Wed, 7 Jan 2009, Dave Kleikamp wrote:
> 
> Do you need to even do that if CONFIG_DEBUG_PAGEALLOC is unset?

No.

> Something like:
> 
> #ifdef CONFIG_DEBUG_PAGEALLOC
>                 /*
>                  * Need to access the cpu field knowing that
>                  * DEBUG_PAGEALLOC could have unmapped it if
>                  * the mutex owner just released it and exited.
>                  */
>                 if (probe_kernel_address(&thread->cpu, cpu))
>                         break;
> #else
> 		cpu = thread->cpu;
> #endif

yes. That would work fine.

			Linus
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