Lennart Sorensen <[email protected]> writes: > And to make it even more annoying to track down: > > It doesn't fail on a power6, only on a power7. power7 machines are > known to have found numerous powerpc memory barrier bugs in code > (including compiler and library code), where earlier generations let > you get away with stuff that the architecture didn't actually allow, > but which usually worked. > > So it seems to be a bug trigged by: vmx code used with openmp with libc > 2.13 on power7. Change any one of those 4 things, and the bug > vanishes.
As far as I can see, this is all still consistent with the bug being that the VMX combiners are writing outside the malloced memory: - Disable OpenMP, and it doesn't matter because the same bytes are read and written. With OpenMP, two threads can mess each other's memory up. - Use different libc: malloc() may allocate different amounts of memory so that the combiners don't write outside of the allocated area. - Disable VMX: There is no writing outside the malloc()ed area - Power 6: Could just be timing differences, but may also have to do with different atomicity of the incorrect memory accesses. Søren _______________________________________________ Pixman mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/pixman
