Re: [linux-pm] [uclinux-dist-devel] freezer: should barriers besmp ?

From: Pavel Machek
Date: Fri Apr 15 2011 - 12:29:44 EST


> > > I believe the code is correct as is.
> >
> > that isnt what the code / documentation says. unless i'm reading them
> > wrong, both seem to indicate that the proposed patch is what we
> > actually want.
> The existing code is correct but it isn't optimal.
> wmb() and rmb() are heavy-duty operations, and you don't want to call
> them when they aren't needed. That's exactly what smp_wmb() and
> smp_rmb() are for -- they call wmb() and rmb(), but only in SMP
> kernels.
> Unless you need to synchronize with another processor (not necessarily
> a CPU, it could be something embedded within a device), you should
> always use smp_wmb() and smp_rmb() rather than wmb() and rmb().

Maybe; but this code is not performance critical and I believe being
obvious here is better...
(cesky, pictures)
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