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David Howells writes: > + CPU 1 CPU 2 COMMENT > + =============== =============== ======================================= > + a == 0, b == 1 and p == &a, q == &a > + b = 2; > + smp_wmb(); Make sure b is changed before p > + p = &b; q = p; > + d = *q; > + > +then old data values may be used in the address calculation for the second > +value, potentially resulting in q == &b and d == 0 being seen, which is never > +correct. What is required is a data dependency memory barrier: No, that's not the problem. The problem is that you can get q == &b and d == 1, believe it or not. That is, you can see the new value of the pointer but the old value of the thing pointed to. Paul. - 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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