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Date: Thu, 9 Aug 2007 10:14:19 +0200 From: Heiko Carstens <heiko.carstens@...ibm.com> To: Chris Snook <csnook@...hat.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, akpm@...ux-foundation.org, ak@...e.de, 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 Thu, Aug 09, 2007 at 03:31:10AM -0400, Chris Snook wrote: > Linus Torvalds wrote: > > 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 > > Fair enough. Casting to (volatile int *) will give us the behavior people > expect when using atomic_t without needing to use inefficient barriers. > > While we have the hood up, should we convert all the atomic_t's to > non-volatile and put volatile casts in all the atomic_reads? I don't know > enough about the various arches to say with confidence that those changes > alone will preserve existing behavior. We might need some arch-specific > tweaking of the atomic operations. If you write that patch could you include the atomic64 variants as well, please? Besides that just post the patch to linux-arch and maintainers should speak up. - 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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