Hi all, I've been trying to debug some data races in an application that uses Boost.Thread. I tried running valgrind's DRD tool against my binary to see if it could locate the source of the problem. It produced more errors than I expected, so I progressively removed portions of my application unless I was left with almost nothing. I found that even with the most minimal program I could produce, the DRD tool still reported errors - in fact, it even reported errors with the examples included with the Boost distribution! I was able to reproduce this behavior on Mac OS X 10.5.7 with Boost 1.39, and on Ubuntu 9.04 with Boost 1.37. Here are steps to reproduce the problem: 1. Build the sample program thread.cpp included in the Boost distribution in libs/thread/example. For Boost 1.39, I used the following command: g++ -L<Boost lib directory> -lboost_thread-xgcc40-mt-1_39 thread.cpp - o thread 2. Run it using valgrind's DRD tool: valgrind --tool=drd --var-info=yes ./thread On Mac OS X 10.5.7, I get the following output: ==20729== drd, a thread error detector. ==20729== Copyright (C) 2006-2009, and GNU GPL'd, by Bart Van Assche. ==20729== Using Valgrind-3.5.0.SVN and LibVEX; rerun with -h for copyright info ==20729== Command: ./thread ==20729== --20729-- ./thread: --20729-- dSYM directory is missing; consider using --auto-run- dsymutil=yes setting alarm for 5 seconds... ==20729== Conflicting load by thread 1 at 0x00012018 size 4 ==20729== at 0x58B1: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x390C: boost::thread::join() (in ./thread) ==20729== by 0x9A13: main (in ./thread) ==20729== Allocation context: Data section of ./thread ==20729== Other segment start (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x5993: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x39BC2: pthread_mutex_unlock (drd_pthread_intercepts.c:633) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment start (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x58D2: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x39BC2: pthread_mutex_unlock (drd_pthread_intercepts.c:633) ==20729== by 0x5988: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== ==20729== Conflicting load by thread 1 at 0x00012014 size 4 ==20729== at 0x58B4: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x390C: boost::thread::join() (in ./thread) ==20729== by 0x9A13: main (in ./thread) ==20729== Allocation context: Data section of ./thread ==20729== Other segment start (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x5993: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x39BC2: pthread_mutex_unlock (drd_pthread_intercepts.c:633) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment start (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x58D2: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x39BC2: pthread_mutex_unlock (drd_pthread_intercepts.c:633) ==20729== by 0x5988: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== ==20729== Conflicting load by thread 1 at 0x00013b5c size 4 ==20729== at 0x993A: boost::detail::get_once_per_thread_epoch() (in ./thread) ==20729== by 0x58BA: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x390C: boost::thread::join() (in ./thread) ==20729== by 0x9A13: main (in ./thread) ==20729== Allocation context: Data section of ./thread ==20729== Other segment start (thread 2) ==20729== at 0x227FF0: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x58D2: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== ==20729== Conflicting load by thread 1 at 0x00013b5c size 4 ==20729== at 0x9972: boost::detail::get_once_per_thread_epoch() (in ./thread) ==20729== by 0x58BA: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x390C: boost::thread::join() (in ./thread) ==20729== by 0x9A13: main (in ./thread) ==20729== Allocation context: Data section of ./thread ==20729== Other segment start (thread 2) ==20729== at 0x227FF0: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x58D2: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== ==20729== Conflicting load by thread 1 at 0x00397680 size 4 ==20729== at 0x20038D: pthread_setspecific (in /usr/lib/ libSystem.B.dylib) ==20729== by 0x997F: boost::detail::get_once_per_thread_epoch() (in ./thread) ==20729== by 0x58BA: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x390C: boost::thread::join() (in ./thread) ==20729== by 0x9A13: main (in ./thread) ==20729== Allocation context: Data section of /usr/lib/libSystem.B.dylib ==20729== Other segment start (thread 2) ==20729== at 0x227FF0: thread_start (in /usr/lib/libSystem.B.dylib) ==20729== Other segment end (thread 2) ==20729== at 0x396B3: pthread_mutex_lock (drd_pthread_intercepts.c: 580) ==20729== by 0x58D2: void boost::call_once<void (*) ()>(boost::once_flag&, void (*)()) (in ./thread) ==20729== by 0x30CC: thread_proxy (in ./thread) ==20729== by 0x3707B: vgDrd_thread_wrapper (drd_pthread_intercepts.c:272) ==20729== by 0x228154: _pthread_start (in /usr/lib/libSystem.B.dylib) ==20729== by 0x228011: thread_start (in /usr/lib/libSystem.B.dylib) alarm sounded... ==20729== ==20729== ERROR SUMMARY: 5 errors from 5 contexts (suppressed: 725 from 8) The output on linux is similar. Does this indicate a problem with valgrind's DRD tool, Boost.Thread, or both? Does any workaround exist? Thanks in advance, - Seth Fowler