On 04/27/2012 10:23 AM, Leonard Plentz wrote: > X is 4 bytes wide. It's based at address 27. Y is also 4 bytes wide. > It's based at address 31. Cache lines happen to be 32 bytes long. > Processor 0 can write to X any time, and processor 1 can write to Y > anytime. Writing to Y causes an implicit read-modify-write to the line > containing X. But this doesn't matter because it's assumed under > C99/C11 that the processor will enforce the orthogonality of X and Y, > provided that their sizes are at least a multiple of whole bytes based > at whole-byte boundaries. > > Is that correct? Yes. If you have a look at the definition of a conflict in N3242=11-0012 you'll see 4 Two expression evaluations conflict if one of them modifies a memory location[1.7] and the other one accesses or modifies the same memory location. ... and in Section 1.7 ... 3 A memory location is either an object of scalar type or a maximal sequence of adjacent bit-fields all having non-zero width. ... Two threads of execution (1.10) can update and access separate memory locations without interfering with each other. Andrew.
