[Bug sanitizer/55561] TSAN: Fortran/OMP yields false positives

["Joost.VandeVondele at mat dot ethz.ch" <gcc-bugzilla at gcc dot gnu dot org>]

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:

vjoost@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out
vjoost@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out
vjoost@nanosim-s01.ethz.ch:/data/vjoost/clean/cp2k/cp2k/src> ./a.out
vjoost@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)

==================