Messages in this thread | | | Subject | Re: [PATCH 0/2] irq_work: A couple fixes | From | Steven Rostedt <> | Date | Tue, 30 Oct 2012 11:52:30 -0400 |
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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.
-- Steve
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