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Date: Fri, 24 Aug 2007 14:07:25 +0200 From: Andi Kleen <ak@...e.de> To: Denys Vlasenko <vda.linux@...glemail.com> Cc: Satyam Sharma <satyam@...radead.org>, Heiko Carstens <heiko.carstens@...ibm.com>, Herbert Xu <herbert@...dor.apana.org.au>, Chris Snook <csnook@...hat.com>, clameter@....com, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org, Linus Torvalds <torvalds@...ux-foundation.org>, netdev@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, davem@...emloft.net, schwidefsky@...ibm.com, wensong@...ux-vs.org, horms@...ge.net.au, wjiang@...ilience.com, cfriesen@...tel.com, zlynx@....org, rpjday@...dspring.com, jesper.juhl@...il.com, segher@...nel.crashing.org Subject: Re: [PATCH] i386: Fix a couple busy loops in mach_wakecpu.h:wait_for_init_deassert() On Friday 24 August 2007 13:59:32 Denys Vlasenko wrote: > On Thursday 16 August 2007 01:39, Satyam Sharma wrote: > > > > static inline void wait_for_init_deassert(atomic_t *deassert) > > { > > - while (!atomic_read(deassert)); > > + while (!atomic_read(deassert)) > > + cpu_relax(); > > return; > > } > > For less-than-briliant people like me, it's totally non-obvious that > cpu_relax() is needed for correctness here, not just to make P4 happy. I find it also non obvious. It would be really better to have a barrier or equivalent (volatile or variable clobber) in the atomic_read() > IOW: "atomic_read" name quite unambiguously means "I will read > this variable from main memory". Which is not true and creates > potential for confusion and bugs. Agreed. -Andi - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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