Chen, Kenneth W wrote:
Christoph Lameter wrote on Thursday, March 30, 2006 6:38 PMNeither 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 -
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