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TSan reports the following data race:
Write of size 4 at 0x000109e0b160 by thread T2 (mutexes: write M0, write M1):
#0 lldb_private::NativeFile::Close() File.cpp:329
(liblldb.18.0.0git.dylib:arm64+0x58dac0)
#1
lldb_private::ConnectionFileDescriptor::Disconnect(lldb_private::Status*)
ConnectionFileDescriptorPosix.cpp:232 (liblldb.18.0.0git.dylib:arm64+0x5bad6c)
#2 lldb_private::Communication::Disconnect(lldb_private::Status*)
Communication.cpp:61 (liblldb.18.0.0git.dylib:arm64+0x451f04)
#3 lldb_private::process_gdb_remote::ProcessGDBRemote::DidExit()
ProcessGDBRemote.cpp:1164 (liblldb.18.0.0git.dylib:arm64+0xadfd80)
#4 lldb_private::Process::SetExitStatus(int, char const*) Process.cpp:1097
(liblldb.18.0.0git.dylib:arm64+0x6ed338)
#5
lldb_private::process_gdb_remote::ProcessGDBRemote::MonitorDebugserverProcess(std::__1::weak_ptr<lldb_private::process_gdb_remote::ProcessGDBRemote>,
unsigned long long, int, int) ProcessGDBRemote.cpp:3387
(liblldb.18.0.0git.dylib:arm64+0xae9464)
Previous read of size 4 at 0x000109e0b160 by main thread (mutexes: write M2):
#0 lldb_private::NativeFile::IsValid() const File.h:393
(liblldb.18.0.0git.dylib:arm64+0x590830)
#1 lldb_private::ConnectionFileDescriptor::IsConnected() const
ConnectionFileDescriptorPosix.cpp:121 (liblldb.18.0.0git.dylib:arm64+0x5b8ab4)
#2 lldb_private::Communication::IsConnected() const Communication.cpp:79
(liblldb.18.0.0git.dylib:arm64+0x451fcc)
#3
lldb_private::process_gdb_remote::GDBRemoteCommunication::WaitForPacketNoLock(StringExtractorGDBRemote&,
lldb_private::Timeout<std::__1::ratio<1l, 1000000l>>, bool)
GDBRemoteCommunication.cpp:256 (liblldb.18.0.0git.dylib:arm64+0xaac060)
#4
lldb_private::process_gdb_remote::GDBRemoteCommunication::WaitForPacketNoLock(StringExtractorGDBRemote&,
lldb_private::Timeout<std::__1::ratio<1l, 1000000l>>, bool)
GDBRemoteCommunication.cpp:244 (liblldb.18.0.0git.dylib:arm64+0xaabe78)
#5
lldb_private::process_gdb_remote::GDBRemoteClientBase::SendPacketAndWaitForResponseNoLock(llvm::StringRef,
StringExtractorGDBRemote&) GDBRemoteClientBase.cpp:246
(liblldb.18.0.0git.dylib:arm64+0xaaa184)
The problem is that in `WaitForPacketNoLock`'s run loop, it checks that the
connection is still connected. This races with the `ConnectionFileDescriptor`
disconnecting. Most (but not all) access to the `IOObject` in
`ConnectionFileDescriptorPosix` is already gated by the mutex. This patch just
protects `IsConnected` in the same way.
https://reviews.llvm.org/D157347
Files:
lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
Index: lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
===================================================================
--- lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
+++ lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
@@ -118,6 +118,7 @@
}
bool ConnectionFileDescriptor::IsConnected() const {
+ std::lock_guard<std::recursive_mutex> guard(m_mutex);
return m_io_sp && m_io_sp->IsValid();
}
Index: lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
===================================================================
--- lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
+++ lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
@@ -131,7 +131,7 @@
lldb::IOObjectSP m_io_sp;
Pipe m_pipe;
- std::recursive_mutex m_mutex;
+ mutable std::recursive_mutex m_mutex;
std::atomic<bool> m_shutting_down; // This marks that we are shutting down so
// if we get woken up from
// BytesAvailable to disconnect, we won't try to read again.
Index: lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
===================================================================
--- lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
+++ lldb/source/Host/posix/ConnectionFileDescriptorPosix.cpp
@@ -118,6 +118,7 @@
}
bool ConnectionFileDescriptor::IsConnected() const {
+ std::lock_guard<std::recursive_mutex> guard(m_mutex);
return m_io_sp && m_io_sp->IsValid();
}
Index: lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
===================================================================
--- lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
+++ lldb/include/lldb/Host/posix/ConnectionFileDescriptorPosix.h
@@ -131,7 +131,7 @@
lldb::IOObjectSP m_io_sp;
Pipe m_pipe;
- std::recursive_mutex m_mutex;
+ mutable std::recursive_mutex m_mutex;
std::atomic<bool> m_shutting_down; // This marks that we are shutting down so
// if we get woken up from
// BytesAvailable to disconnect, we won't try to read again.
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