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Chen, Kenneth W wrote: > Christoph Lameter wrote on Thursday, March 30, 2006 6:38 PM > >>>>Neither one is correct because there will always be one combination of >>>>clear_bit with these macros that does not generate the required memory >>>>barrier. >>> >>>Can you give an example? Which combination? >> >>For Option(1) >> >>smp_mb__before_clear_bit() >>clear_bit(...)( > > > Sorry, you totally lost me. It could me I'm extremely slow today. For > option (1), on ia64, clear_bit has release semantic already. The comb > of __before_clear_bit + clear_bit provides the required ordering. Did > I miss something? By the way, we are talking about detail implementation > on one specific architecture. Not some generic concept that clear_bit > has no ordering stuff in there. > The memory ordering that above combination should produce is a Linux style smp_mb before the clear_bit. Not a release. -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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