Hi there, I am looking at the test-lock failure reported by (1) while findutils building in opensuse for ppc64le architecture. Helgrind is reporting data race for the three *_checker_done volatiles as summarized in (2)
Is is a false positive or a real problem ? (1) https://bugzilla.suse.com/show_bug.cgi?id=923486 (2) extract of helgrind output (full log in attachment) === $valgrind --tool=helgrind ./test-lock ... ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during write of size 4 at 0x102BED4C by thread #1 ==1408== Locks held: none ==1408== at 0x10001078: test_rwlock (test-lock.c:300) ==1408== by 0x10001078: main (test-lock.c:577) ==1408== ==1408== This conflicts with a previous read of size 4 by thread #17 ==1408== Locks held: none ==1408== at 0x10002118: rwlock_checker_thread (test-lock.c:264) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== Address 0x102bed4c is 0 bytes inside data symbol "rwlock_checker_done" ==1408== ==1408== ---------------------------------------------------------------- === === related source code: === findutils-4.5.14/tests/test-lock.c:215: lock_checker_done = 1; findutils-4.5.14/tests/test-lock.c:180: while (!lock_checker_done) === findutils-4.5.14/tests/test-lock.c:264: while (!rwlock_checker_done) findutils-4.5.14/tests/test-lock.c:300: rwlock_checker_done = 1; === findutils-4.5.14/tests/test-lock.c:366: while (!reclock_checker_done) findutils-4.5.14/tests/test-lock.c:401: reclock_checker_done = 1; === -- Michel Normand
@vm64:/home/michel[michel@vm64:~] $/cd $cd /mnt/disk3/build-root/standard-ppc64le/home/abuild/rpmbuild/BUILD/findutils-4.5.14/tests/ $ [michel@vm64:/mnt/disk3/build-root/standard-ppc64le/home/abuild/rpmbuild/BUILD/findutils-4.5.14/tests ] $valgrind --tool=helgrind ./test-lock ==1408== Helgrind, a thread error detector ==1408== Copyright (C) 2007-2013, and GNU GPL'd, by OpenWorks LLP et al. ==1408== Using Valgrind-3.10.0 and LibVEX; rerun with -h for copyright info ==1408== Command: ./test-lock ==1408== Starting test_lock ...==1408== ---Thread-Announcement------------------------------------------ ==1408== ==1408== Thread #1 is the program's root thread ==1408== ==1408== ---Thread-Announcement------------------------------------------ ==1408== ==1408== Thread #2 was created ==1408== at 0x41FE058: clone (clone.S:77) ==1408== by 0x40B7807: create_thread (createthread.c:102) ==1408== by 0x406C1DB: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x10000EB7: gl_thread_create (thread.h:383) ==1408== by 0x10000EB7: test_lock (test-lock.c:208) ==1408== by 0x10000EB7: main (test-lock.c:572) ==1408== ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during write of size 4 at 0x10013208 by thread #1 ==1408== Locks held: none ==1408== at 0x10000F40: test_lock (test-lock.c:215) ==1408== by 0x10000F40: main (test-lock.c:572) ==1408== ==1408== This conflicts with a previous read of size 4 by thread #2 ==1408== Locks held: none ==1408== at 0x10001C78: lock_checker_thread (test-lock.c:180) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== Address 0x10013208 is 0 bytes inside data symbol "lock_checker_done" ==1408== ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during read of size 4 at 0x10013208 by thread #2 ==1408== Locks held: none ==1408== at 0x10001C78: lock_checker_thread (test-lock.c:180) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== ==1408== This conflicts with a previous write of size 4 by thread #1 ==1408== Locks held: none ==1408== at 0x10000F40: test_lock (test-lock.c:215) ==1408== by 0x10000F40: main (test-lock.c:572) ==1408== Address 0x10013208 is 0 bytes inside data symbol "lock_checker_done" ==1408== OK Starting test_rwlock ...==1408== ---Thread-Announcement------------------------------------------ ==1408== ==1408== Thread #17 was created ==1408== at 0x41FE058: clone (clone.S:77) ==1408== by 0x40B7807: create_thread (createthread.c:102) ==1408== by 0x406C1DB: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x10000FF7: gl_thread_create (thread.h:383) ==1408== by 0x10000FF7: test_rwlock (test-lock.c:293) ==1408== by 0x10000FF7: main (test-lock.c:577) ==1408== ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during write of size 4 at 0x102BED4C by thread #1 ==1408== Locks held: none ==1408== at 0x10001078: test_rwlock (test-lock.c:300) ==1408== by 0x10001078: main (test-lock.c:577) ==1408== ==1408== This conflicts with a previous read of size 4 by thread #17 ==1408== Locks held: none ==1408== at 0x10002118: rwlock_checker_thread (test-lock.c:264) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== Address 0x102bed4c is 0 bytes inside data symbol "rwlock_checker_done" ==1408== ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during read of size 4 at 0x102BED4C by thread #17 ==1408== Locks held: none ==1408== at 0x10002118: rwlock_checker_thread (test-lock.c:264) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== ==1408== This conflicts with a previous write of size 4 by thread #1 ==1408== Locks held: none ==1408== at 0x10001078: test_rwlock (test-lock.c:300) ==1408== by 0x10001078: main (test-lock.c:577) ==1408== Address 0x102bed4c is 0 bytes inside data symbol "rwlock_checker_done" ==1408== OK Starting test_recursive_lock ...==1408== ---Thread-Announcement------------------------------------------ ==1408== ==1408== Thread #33 was created ==1408== at 0x41FE058: clone (clone.S:77) ==1408== by 0x40B7807: create_thread (createthread.c:102) ==1408== by 0x406C1DB: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x1000111B: gl_thread_create (thread.h:383) ==1408== by 0x1000111B: test_recursive_lock (test-lock.c:394) ==1408== by 0x1000111B: main (test-lock.c:582) ==1408== ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during write of size 4 at 0x1001320C by thread #1 ==1408== Locks held: none ==1408== at 0x100011A0: test_recursive_lock (test-lock.c:401) ==1408== by 0x100011A0: main (test-lock.c:582) ==1408== ==1408== This conflicts with a previous read of size 4 by thread #33 ==1408== Locks held: none ==1408== at 0x10001E5C: reclock_checker_thread (test-lock.c:366) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== Address 0x1001320c is 0 bytes inside data symbol "reclock_checker_done" ==1408== ==1408== ---------------------------------------------------------------- ==1408== ==1408== Possible data race during read of size 4 at 0x1001320C by thread #33 ==1408== Locks held: none ==1408== at 0x10001E5C: reclock_checker_thread (test-lock.c:366) ==1408== by 0x406C3A3: ??? (in /usr/lib64/valgrind/vgpreload_helgrind-ppc64le-linux.so) ==1408== by 0x40B9453: start_thread (pthread_create.c:335) ==1408== by 0x41FE0C3: clone (clone.S:96) ==1408== ==1408== This conflicts with a previous write of size 4 by thread #1 ==1408== Locks held: none ==1408== at 0x100011A0: test_recursive_lock (test-lock.c:401) ==1408== by 0x100011A0: main (test-lock.c:582) ==1408== Address 0x1001320c is 0 bytes inside data symbol "reclock_checker_done" ==1408== OK Starting test_once ...Killed === === related source code: === findutils-4.5.14/tests/test-lock.c:215: lock_checker_done = 1; findutils-4.5.14/tests/test-lock.c:180: while (!lock_checker_done) === findutils-4.5.14/tests/test-lock.c:264: while (!rwlock_checker_done) findutils-4.5.14/tests/test-lock.c:300: rwlock_checker_done = 1; === findutils-4.5.14/tests/test-lock.c:366: while (!reclock_checker_done) findutils-4.5.14/tests/test-lock.c:401: reclock_checker_done = 1; === === ===
