[lldb] Fixed lldb-server crash (TestLogHandler was not thread safe) #101326
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Host::LaunchProcess() requires to SetMonitorProcessCallback. This callback is called from the child process monitor thread. We cannot control this thread anyway. lldb-server may crash if there is a logging around this callback because TestLogHandler is not thread safe. I faced this issue debugging 100 simultaneous child processes. Note StreamLogHandler::Emit() in lldb/source/Utility/Log.cpp already contains the similar mutex.
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@llvm/pr-subscribers-lldb Author: Dmitry Vasilyev (slydiman) ChangesHost::LaunchProcess() requires to SetMonitorProcessCallback. This callback is called from the child process monitor thread. We cannot control this thread anyway. lldb-server may crash if there is a logging around this callback because TestLogHandler is not thread safe. I faced this issue debugging 100 simultaneous child processes. Note StreamLogHandler::Emit() in lldb/source/Utility/Log.cpp already contains the similar mutex. Full diff: https://github.com/llvm/llvm-project/pull/101326.diff 1 Files Affected:
diff --git a/lldb/tools/lldb-server/LLDBServerUtilities.cpp b/lldb/tools/lldb-server/LLDBServerUtilities.cpp
index c3a8df19e969e..5facfbf3105e9 100644
--- a/lldb/tools/lldb-server/LLDBServerUtilities.cpp
+++ b/lldb/tools/lldb-server/LLDBServerUtilities.cpp
@@ -27,11 +27,13 @@ class TestLogHandler : public LogHandler {
: m_stream_sp(stream_sp) {}
void Emit(llvm::StringRef message) override {
+ std::lock_guard<std::mutex> guard(m_mutex);
(*m_stream_sp) << message;
m_stream_sp->flush();
}
private:
+ std::mutex m_mutex;
std::shared_ptr<raw_ostream> m_stream_sp;
};
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slydiman
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…t on Windows `lldb-server platform --server` works on Windows now w/o multithreading. The rest functionality remains unchanged. Added also PipeWindows::WriteWithTimeout(), fixed PipeWindows::ReadWithTimeout() and missing initialization of m_read_overlapped.hEvent in the constructor PipeWindows(lldb::pipe_t read, lldb::pipe_t write). Fixes llvm#90923, fixes llvm#56346. Depends on llvm#101326. This is the part 1 of the replacement of llvm#100670. In the part 2 I plan to switch `lldb-server gdbserver` to use `--fd` and listen a common gdb port for all gdbserver connections. Then we can remove gdb port mapping to fix llvm#97537.
labath
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Jul 31, 2024
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This makes sense, though it would probably be even better to just use the real StreamLogHandler class. I think all that's needed would be to add a new constructor to it.
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Host::LaunchProcess() requires to SetMonitorProcessCallback. This callback is called from the child process monitor thread. We cannot control this thread anyway. lldb-server may crash if there is a logging around this callback because TestLogHandler is not thread safe. I faced this issue debugging 100 simultaneous child processes. Note StreamLogHandler::Emit() in lldb/source/Utility/Log.cpp already contains the similar mutex.