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

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Message-ID: <alpine.DEB.1.10.0901072130110.29075@gandalf.stny.rr.com>
Date:	Wed, 7 Jan 2009 21:33:31 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Dave Kleikamp <shaggy@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.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, Linus Torvalds wrote:
> > Should that be:
> > 
> > #if defined(CONFIG_DEBUG_PAGEALLOC) || defined(CONFIG_MEMORY_HOTPLUG)
> 
> Well, probably CONFIG_MEMORY_HOTREMOVE, no? And I'd actually suggest that 
> unplugging should have a stop-machine if it doesn't already, just because 
> it's such a special case - like module removal.

I do not think stop-machine will help, unless that spinning is protected 
by preempt-disable. If the task gets preempted after grabbing the owner 
thread_info, and then stop-machine runs, the memory disappears, the task 
is scheduled back, accesses the owner thread_info and then page-fault.

-- Steve

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