On Tue, May 27, 2014 at 11:00 PM, Jakub Jelinek <ja...@redhat.com> wrote: > On Tue, May 27, 2014 at 11:50:33PM +0200, Jakub Jelinek wrote: >> On Tue, May 27, 2014 at 04:02:08PM -0500, Peter Bergner wrote: >> > It's being called form basically two files: >> > >> > [bergner@makalu-lp1 gcc-fsf-mainline-asan-debug]$ find . -name '*.o' | >> > xargs nm -AC | grep sync_fetch_and_add_8 >> > ./powerpc64-linux/32/libsanitizer/sanitizer_common/.libs/sanitizer_allocator.o: >> > U __sync_fetch_and_add_8 >> > ./powerpc64-linux/32/libsanitizer/sanitizer_common/sanitizer_allocator.o: >> > U __sync_fetch_and_add_8 >> > ./powerpc64-linux/32/libsanitizer/asan/.libs/asan_allocator2.o: U >> > __sync_fetch_and_add_8 >> > ./powerpc64-linux/32/libsanitizer/asan/asan_allocator2.o: U >> > __sync_fetch_and_add_8 >> >> Does ppc32 have any atomic 64-bit loads/stores (in the sense that the aligned >> 64 bits are written as one memory transaction, not each 32-bit word >> separately)? >> In any case, atomic_uint64_t there seems to be used only for some statistic >> counter and not really atomic anyway, as additions aren't performed using >> atomic instructions, but just atomic load, followed by normal arithmetics, >> followed by atomic store. >> Can't 32-bit counters be used instead on 32-bit arches? >> >> I see there is another spot with atomic_uint64_t in sanitizer_lfstack.h, >> but for some reason it isn't used now at all (there it would want to use >> 64-bit compare and exchange). > > On ARM, while it supposedly links, because __sync_compare_and_exchange_8 > is defined in libgcc.a, it will only work with post-2011 kernels and is > going to be very slow (because you do a separate compare and exchange
FTR, this call down to the library function should only be for legacy architectures. On ARM we have a 64 bit atomic compare and exchange which can be done with the ldrexd / strexd instructions at the right architecture level (v6k and above IIRC). Ramana
