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Message-ID: <20110415162938.GA11454@atrey.karlin.mff.cuni.cz> Date: Fri, 15 Apr 2011 18:29:38 +0200 From: Pavel Machek <pavel@....cz> To: Alan Stern <stern@...land.harvard.edu> Cc: Mike Frysinger <vapier@...too.org>, uclinux-dist-devel@...ckfin.uclinux.org, linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [linux-pm] [uclinux-dist-devel] freezer: should barriers be smp ? Hi! > > > 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... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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