From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3993 invoked by alias); 29 Dec 2012 09:38:37 -0000 Received: (qmail 2272 invoked by uid 55); 29 Dec 2012 09:38:15 -0000 From: "dvyukov at google dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug sanitizer/55561] TSAN: Fortran/OMP yields false positives Date: Sat, 29 Dec 2012 09:38:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: sanitizer X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: dvyukov at google dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-12/txt/msg02415.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55561 --- Comment #19 from Dmitry Vyukov 2012-12-29 09:38:13 UTC --- On Wed, Dec 26, 2012 at 12:23 AM, Joost.VandeVondele at mat dot ethz.ch wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55561 > > --- Comment #16 from Joost VandeVondele 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) 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.