On 9/25/20 5:53 PM, Dmitry Antipov wrote:
On 9/24/20 9:14 PM, Greg Clayton wrote:
This must be a valgrind issue, there would be major problems if the OS isn't able to lock mutex objects correctly ("mutex is locked simultaneously by two threads"). It is getting confused by a
recursive mutex? LLDB uses recursive mutexes.
LLDB's Predicate.h uses plain std::mutex, which is not recursive, and
std::lock_guard/std::unique_lock
on top of it.
This needs more digging in because the latest Valgrind snapshot reports the same
"impossible" condition.
To whom it may be interesting, thread sanitizer reports nearly the same:
WARNING: ThreadSanitizer: double lock of a mutex (pid=2049545)
#0 pthread_mutex_lock <null> (libtsan.so.0+0x528ac)
#1 __gthread_mutex_lock
/usr/include/c++/10/x86_64-redhat-linux/bits/gthr-default.h:749
(liblldb.so.12git+0xd725c0)
#2 std::mutex::lock() /usr/include/c++/10/bits/std_mutex.h:100
(liblldb.so.12git+0xd725c0)
#3 std::lock_guard<std::mutex>::lock_guard(std::mutex&)
/usr/include/c++/10/bits/std_mutex.h:159 (liblldb.so.12git+0xd725c0)
#4 lldb_private::Predicate<bool>::SetValue(bool,
lldb_private::PredicateBroadcastType)
/home/antipov/llvm/source/lldb/include/lldb/Utility/Predicate.h:91
(liblldb.so.12git+0xd725c0)
#5 lldb_private::EventDataReceipt::DoOnRemoval(lldb_private::Event*)
/home/antipov/llvm/source/lldb/include/lldb/Utility/Event.h:121
(liblldb.so.12git+0xd725c0)
#6 lldb_private::Event::DoOnRemoval()
/home/antipov/llvm/source/lldb/source/Utility/Event.cpp:82
(liblldb.so.12git+0xedb7da)
#7 lldb_private::Listener::FindNextEventInternal(std::unique_lock<std::mutex>&, lldb_private::Broadcaster*, lldb_private::ConstString const*, unsigned int, unsigned int,
std::shared_ptr<lldb_private::Event>&, bool) /home/antipov/llvm/source/lldb/source/Utility/Listener.cpp:309 (liblldb.so.12git+0xee6099)
#8 lldb_private::Listener::GetEventInternal(lldb_private::Timeout<std::ratio<1l, 1000000l> > const&, lldb_private::Broadcaster*, lldb_private::ConstString const*, unsigned int, unsigned int,
std::shared_ptr<lldb_private::Event>&) /home/antipov/llvm/source/lldb/source/Utility/Listener.cpp:357 (liblldb.so.12git+0xee6b63)
#9 lldb_private::Listener::GetEventForBroadcaster(lldb_private::Broadcaster*, std::shared_ptr<lldb_private::Event>&, lldb_private::Timeout<std::ratio<1l, 1000000l> > const&)
/home/antipov/llvm/source/lldb/source/Utility/Listener.cpp:395 (liblldb.so.12git+0xee6dea)
#10 lldb_private::Process::GetEventsPrivate(std::shared_ptr<lldb_private::Event>&, lldb_private::Timeout<std::ratio<1l, 1000000l> > const&, bool)
/home/antipov/llvm/source/lldb/source/Target/Process.cpp:1139 (liblldb.so.12git+0xd7931d)
#11 lldb_private::Process::RunPrivateStateThread(bool)
/home/antipov/llvm/source/lldb/source/Target/Process.cpp:3872
(liblldb.so.12git+0xda3648)
#12 lldb_private::Process::PrivateStateThread(void*)
/home/antipov/llvm/source/lldb/source/Target/Process.cpp:3857
(liblldb.so.12git+0xda3f87)
#13 lldb_private::HostNativeThreadBase::ThreadCreateTrampoline(void*)
/home/antipov/llvm/source/lldb/source/Host/common/HostNativeThreadBase.cpp:68
(liblldb.so.12git+0xc2c0ea)
#14 <null> <null> (libtsan.so.0+0x2d33f)
Again, lldb_private::Predicate uses plain std::mutex, which is not recursive.
Dmitry
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