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

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Message-Id: <20090108114905.3190b045.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 8 Jan 2009 11:49:05 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	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 21:33:31 -0500 (EST)
Steven Rostedt <rostedt@...dmis.org> wrote:

> 
> 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.
> 
How about recording "cpu" into mutex at locking explicitly  ?
too bad ?

-Kame

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