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Date: Mon, 04 Nov 2013 07:57:41 +1100 From: Benjamin Herrenschmidt <benh@...nel.crashing.org> To: Victor Kaplansky <VICTORK@...ibm.com> Cc: David Laight <David.Laight@...lab.com>, Michael Neuling <mikey@...ling.org>, Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>, Peter Zijlstra <peterz@...radead.org>, Frederic Weisbecker <fweisbec@...il.com>, LKML <linux-kernel@...r.kernel.org>, Oleg Nesterov <oleg@...hat.com>, Linux PPC dev <linuxppc-dev@...abs.org>, Anton Blanchard <anton@...ba.org>, paulmck@...ux.vnet.ibm.com Subject: Re: perf events ring buffer memory barrier on powerpc On Fri, 2013-11-01 at 18:30 +0200, Victor Kaplansky wrote: > "David Laight" <David.Laight@...lab.com> wrote on 11/01/2013 06:25:29 PM: > > gcc will do unexpected memory accesses for bit fields that are > > adjacent to volatile data. > > In particular it may generate 64bit sized (and aligned) RMW cycles > > when accessing bit fields. > > And yes, this has caused real problems. > > Thanks, I am aware about this bug/feature in gcc. AFAIK, this has been fixed in 4.8 and 4.7.3 ... Cheers, Ben. > -- Victor > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@...ts.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev -- 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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