Date: Thu, 8 Jan 2009 11:49:05 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
       Dave Kleikamp <shaggy@linux.vnet.ibm.com>,
       Peter Zijlstra <peterz@infradead.org>, paulmck@linux.vnet.ibm.com,
       Gregory Haskins <ghaskins@novell.com>, Ingo Molnar <mingo@elte.hu>,
       Matthew Wilcox <matthew@wil.cx>, Andi Kleen <andi@firstfloor.org>,
       Chris Mason <chris.mason@oracle.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       linux-fsdevel <linux-fsdevel@vger.kernel.org>,
       linux-btrfs <linux-btrfs@vger.kernel.org>,
       Thomas Gleixner <tglx@linutronix.de>, Nick Piggin <npiggin@suse.de>,
       Peter Morreale <pmorreale@novell.com>,
       Sven Dietrich <SDietrich@novell.com>
Subject: Re: [PATCH -v5][RFC]: mutex: implement adaptive spinning
Message-Id: <20090108114905.3190b045.kamezawa.hiroyu@jp.fujitsu.com>
In-Reply-To: <alpine.DEB.1.10.0901072130110.29075@gandalf.stny.rr.com>
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	<alpine.DEB.1.10.0901071848431.23456@gandalf.stny.rr.com>
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On Wed, 7 Jan 2009 21:33:31 -0500 (EST)
Steven Rostedt <rostedt@goodmis.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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