Messages in this thread | | | Date | Tue, 20 Dec 2005 09:10:22 -0500 (EST) | From | Nicolas Pitre <> | Subject | Re: [patch 04/15] Generic Mutex Subsystem, add-atomic-call-func-x86_64.patch |
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On Tue, 20 Dec 2005, Nick Piggin wrote:
> Nicolas Pitre wrote: > > On Tue, 20 Dec 2005, Ingo Molnar wrote: > > > > > > > * David Woodhouse <dwmw2@infradead.org> wrote: > > > > > > > > > > On Mon, 2005-12-19 at 09:49 -0800, Zwane Mwaikambo wrote: > > > > > > > > > Hi Ingo, > > > > > Doesn't this corrupt caller saved registers? > > > > > > > > Looks like it. I _really_ don't like calling functions from inline asm. > > > > It's not nice. Can't we use atomic_dec_return() for this? > > > > > > we can use atomic_dec_return(), but that will add one more instruction to > > > the fastpath. OTOH, atomic_dec_return() is available on every > > > architecture, so it's a really tempting thing. I'll experiment with it. > > > > > > Please consider using (a variant of) xchg() instead. Although atomic_dec() > > is available on all architectures, its implementation is far from being the > > most efficient thing to do for them all. For example, see my discussion > > about swp on ARM: > > > > Considering that on UP, the arm should not need to disable interrupts > for this function (or has someone refuted Linus?), how about:
Kernel preemption.
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