http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55561
--- Comment #19 from Dmitry Vyukov <dvyukov at google dot com> 2012-12-29 09:38:13 UTC --- On Wed, Dec 26, 2012 at 12:23 AM, Joost.VandeVondele at mat dot ethz.ch <gcc-bugzi...@gcc.gnu.org> wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55561 > > --- Comment #16 from Joost VandeVondele <Joost.VandeVondele at mat dot > ethz.ch> 2012-12-25 20:23:07 UTC --- > many things appear to work fine, but seemingly parallel do loops with a > dynamic > schedule generate warnings in libgomp. I also seem to observe that they are > not > strictly deterministic, sometimes these warnings happen, sometimes not. > > Testcase: > > !$OMP PARALLEL PRIVATE(j) > > j=OMP_GET_THREAD_NUM() > > ! no warnings without the dynamic schedule > !$OMP DO SCHEDULE(DYNAMIC,2) > DO i=1,10 > ENDDO > > !$OMP END PARALLEL > END > > Result: > > vjo...@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out > vjo...@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out > vjo...@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out > vjo...@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out > ================== > WARNING: ThreadSanitizer: data race (pid=35190) > Read of size 8 at 0x7d3000027290 by main thread: > #0 gomp_iter_dynamic_next > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/iter.c:190 > (libgomp.so.1+0x000000006678) > #1 GOMP_loop_dynamic_start > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/loop.c:128 > (libgomp.so.1+0x000000007a03) > #2 MAIN__._omp_fn.0 test.f90:0 (exe+0x000000000d7d) > #3 MAIN__ test.f90:0 (exe+0x000000000ccb) > #4 main ??:0 (exe+0x000000000d1a) > > Previous write of size 8 at 0x7d3000027290 by thread 1: > #0 gomp_loop_init > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/loop.c:41 > (libgomp.so.1+0x000000007a96) > #1 MAIN__._omp_fn.0 test.f90:0 (exe+0x000000000d7d) > #2 gomp_thread_start > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/team.c:116 > (libgomp.so.1+0x00000000d012) > > Location is heap block of size 1568 at 0x7d3000027100 allocated by main > thread: > #0 malloc ??:0 (libtsan.so.0+0x00000001896e) > #1 gomp_malloc > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/alloc.c:36 > (libgomp.so.1+0x00000000417a) > #2 gomp_new_team > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/team.c:145 > (libgomp.so.1+0x00000000d27a) > #3 GOMP_parallel_start > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/parallel.c:108 > (libgomp.so.1+0x00000000afc7) > #4 MAIN__ test.f90:0 (exe+0x000000000cc1) > #5 main ??:0 (exe+0x000000000d1a) > > Thread 1 (tid=35191, running) created at: > #0 pthread_create ??:0 (libtsan.so.0+0x00000001a868) > #1 gomp_team_start > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/team.c:440 > (libgomp.so.1+0x00000000d908) > #2 GOMP_parallel_start > /data/vjoost/gnu/gcc_trunk/obj/x86_64-unknown-linux-gnu/libgomp/../../../gcc/libgomp/parallel.c:108 > (libgomp.so.1+0x00000000afd7) > #3 MAIN__ test.f90:0 (exe+0x000000000cc1) > #4 main ??:0 (exe+0x000000000d1a) Looks like unsafe publication of gomp_work_share data. Can you show disassembly of > #2 MAIN__._omp_fn.0 test.f90:0 (exe+0x000000000d7d) ? How does it choose between calling gomp_loop_init() and GOMP_loop_dynamic_start()? Humm... do omp generated functions (like MAIN__._omp_fn.0) pass through tsan pass? Perhaps it contains some atomic op that tsan does not see.
