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From: "lewis at sophists dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug sanitizer/101978] thread sanitizer false positive when condition variable
Date: Thu, 28 Jul 2022 15:36:00 +0000 [thread overview]
Message-ID: <bug-101978-4-6wqvQdbFeb@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-101978-4@http.gcc.gnu.org/bugzilla/>
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101978
lewis pringle <lewis at sophists dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |lewis at sophists dot com
--- Comment #5 from lewis pringle <lewis at sophists dot com> ---
I have a (limited) trace of some of my code running into this problem. And even
without the code, the trace is strongly enough suggestive of where the problem
is I thought it worth including:
TSAN_OPTIONS="detect_deadlocks=0
suppressions=/Sandbox/Stroika-Dev//Tests/ThreadSanitizerSuppressions_qCompiler_SanitizerDoubleLockWithConditionVariables_Buggy.supp"
Builds/g++-debug-sanitize_thread/Tests/Test40
139746996119104] ENtering lock
139747039984064]ENtering try_lock_for
139747039984064]and the try_lock_for returned 0
139747039984064]ENtering try_lock_for
139747039984064]and the try_lock_for returned 0
139746996119104] Entering unlock
139747039984064]ENtering try_lock_for
139747039984064]and the try_lock_for returned 1
139747039984064] Entering unlock
==================
WARNING: ThreadSanitizer: unlock of an unlocked mutex (or by a wrong thread)
(pid=271643)
#0 pthread_mutex_unlock <null> (Test40+0x8a4a88)
#1 __gthread_mutex_unlock
/usr/include/x86_64-linux-gnu/c++/11/bits/gthr-default.h:779 (Test40+0x943790)
#2 __gthread_recursive_mutex_unlock
/usr/include/x86_64-linux-gnu/c++/11/bits/gthr-default.h:832 (Test40+0x943800)
#3 std::recursive_timed_mutex::unlock() <null> (Test40+0x97621d)
#4 unlock /Sandbox/Stroika-Dev/Tests/40/Test.cpp:1380 (Test40+0x94ee9f)
#5 unlock /usr/include/c++/11/bits/unique_lock.h:195 (Test40+0x968fed)
#6 ~unique_lock /usr/include/c++/11/bits/unique_lock.h:104
(Test40+0x95f342)
#7 ~ReadableReference
/Sandbox/Stroika-Dev/Library/Sources/Stroika/Foundation/Characters/../Execution/Synchronized.inl:447
(Test40+0x95849c)
it appears the problem is that (at least one) problem is that use of
try_lock_for () - when it acquires a lock - appears to not do the same
bookkeeping as lock, so that TSAN knows the lock happened and in what thread.
This COULD POSSIBLY be the same root cause of the problems with condition
variables (or maybe unrelated I suppose).
I dont know how TSAN does its magic/tracking, but I'd start looking at if
try_lock_for appears to similar stuff to lock...
next prev parent reply other threads:[~2022-07-28 15:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-19 14:31 [Bug sanitizer/101978] New: thread sanitizer false positive when smart pointers ispavlick at gmail dot com
2021-08-19 16:59 ` [Bug sanitizer/101978] " ispavlick at gmail dot com
2021-08-20 7:53 ` [Bug sanitizer/101978] thread sanitizer false positive when condition variable marxin at gcc dot gnu.org
2022-02-20 6:04 ` danregister at poczta dot fm
2022-07-18 11:35 ` boris at kolpackov dot net
2022-07-28 15:36 ` lewis at sophists dot com [this message]
2022-09-23 14:52 ` jakob.weisblat at zoom dot us
2022-09-23 16:44 ` pinskia at gcc dot gnu.org
2022-09-23 16:47 ` jakob.weisblat at zoom dot us
2022-09-23 17:19 ` redi at gcc dot gnu.org
2022-09-23 18:30 ` redi at gcc dot gnu.org
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