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Date: Wed, 8 Aug 2007 21:18:25 -0700 (PDT) From: Linus Torvalds <torvalds@...ux-foundation.org> To: Chris Snook <csnook@...hat.com> cc: akpm@...ux-foundation.org, ak@...e.de, heiko.carstens@...ibm.com, davem@...emloft.net, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, schwidefsky@...ibm.com, wensong@...ux-vs.org, horms@...ge.net.au, wjiang@...ilience.com, cfriesen@...tel.com, zlynx@....org Subject: Re: [PATCH] make atomic_t volatile on all architectures On Wed, 8 Aug 2007, Chris Snook wrote: > > Some architectures currently do not declare the contents of an atomic_t to be > volatile. This causes confusion since atomic_read() might not actually read > anything if an optimizing compiler re-uses a value stored in a register, which > can break code that loops until something external changes the value of an > atomic_t. I'd be *much* happier with "atomic_read()" doing the "volatile" instead. The fact is, volatile on data structures is a bug. It's a wart in the C language. It shouldn't be used. Volatile accesses in *code* can be ok, and if we have "atomic_read()" expand to a "*(volatile int *)&(x)->value", then I'd be ok with that. But marking data structures volatile just makes the compiler screw up totally, and makes code for initialization sequences etc much worse. Linus - 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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