Messages in this thread | | | Date | Thu, 30 Mar 2006 17:37:45 -0800 (PST) | From | Christoph Lameter <> | Subject | RE: Synchronizing Bit operations V2 |
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On Thu, 30 Mar 2006, Chen, Kenneth W wrote:
> Christoph Lameter wrote on Thursday, March 30, 2006 5:13 PM > > Then there will no barrier since clear_bit only has acquire semantics. > > This is a bug in bit operations since smb_mb__before_clear_bit does > > not work as documentted. > > Well, please make up your mind with: > > Option (1): > > #define clear_bit clear_bit_mode(..., RELEASE) > #define Smp_mb__before_clear_bit do { } while (0) > #define Smp_mb__after_clear_bit smp_mb() > > Or option (2): > > #define clear_bit clear_bit_mode(..., ACQUIRE) > #define Smp_mb__before_clear_bit smp_mb() > #define Smp_mb__after_clear_bit do { } while (0) > > I'm fine with either one.
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.
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