2012/10/30 Steven Rostedt <rost...@goodmis.org>:
> On Tue, 2012-10-30 at 16:34 +0100, Frederic Weisbecker wrote:
>> Hi,
>
>> And I still wonder if cpu_relax() is enough to prevent the compiler
>> from correctly reloading work->flags in irq_work_sync() loop.
>> Do we need ACCESS_ONCE()?
>
> You mean this loop:
>
> flags = work->flags & ~IRQ_WORK_PENDING;
> for (;;) {
> nflags = flags | IRQ_WORK_FLAGS;
> oflags = cmpxchg(&work->flags, flags, nflags);
> if (oflags == flags)
> break;
> if (oflags & IRQ_WORK_PENDING)
> return false;
> flags = oflags;
> cpu_relax();
> }
>
> After the first loading of work->flags, you are worried about the
> &work->flags in the cmpxchg()? The cmpxchg() will handle that itself. I
> don't see any place that a ACCESS_ONCE() is required here. The cmpxchg()
> acts on the address of work->flags, the compiler isn't involved with the
> value at that address.
No I was worried about the cpu_relax() in irq_work_sync()
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