Re: [PATCH] Fix dirty page accounting in redirty_page_for_writepage()

Linus Torvalds
2009-04-30T16:26:14Z

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