[ltt-dev] [PATCH] Fix dirty page accounting in redirty_page_for_writepage()

[torvalds@linux-foundation.org (Linus Torvalds)]

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