From mboxrd@z Thu Jan  1 00:00:00 1970
From: torvalds@linux-foundation.org (Linus Torvalds)
Date: Thu, 30 Apr 2009 09:16:31 -0700 (PDT)
Subject: [ltt-dev] [PATCH] Fix dirty page accounting in
 redirty_page_for_writepage()
In-Reply-To: <20090430160606.GA5913@elte.hu>
References: <20090430133859.GB8329@elte.hu>
	<alpine.DEB.1.10.0904300938220.22262@qirst.com>
	<20090430141446.GD14696@elte.hu>
	<alpine.DEB.1.10.0904301013110.14178@qirst.com>
	<20090430143819.GF14696@elte.hu>
	<alpine.DEB.1.10.0904301042170.4028@qirst.com>
	<20090430150142.GC20580@elte.hu>
	<alpine.DEB.1.10.0904301114440.4028@qirst.com>
	<20090430154255.GA3714@elte.hu>
	<alpine.DEB.1.10.0904301142140.4028@qirst.com>
	<20090430160606.GA5913@elte.hu>
Message-ID: <alpine.LFD.2.00.0904300914110.3395@localhost.localdomain>



On Thu, 30 Apr 2009, Ingo Molnar wrote:
> 
> c0436275:   64 83 05 20 5f 6a c0    addl   $0x1,%fs:0xc06a5f20
> 
> There's no atomic instructions at all - the counters here are only 
> accessed locally. They are local-irq-atomic, but not 
> cacheline-atomic.

On other architectures, you need the whole "disable preemption, 
load-locked, store-conditional, test-and-loop, enable preemption" thing. 

Or "disable interrupts, load, store, restore interrupts".

There really aren't very many architectures that can do almost 
unrestricted ALU ops in a single instruction (and thus automatically safe 
from preemption and interrupts).

			Linus