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Fix a race condition between the Watcher thread and the main thread

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during program exit

A race condition exist between the Watcher thread and main(). A case
was found where the Watcher thread does not get execution time before
the main function returns and calls atexit(). At that point the
Watcher thread started runing tls_init() code while the main thread
was shutting down. This resulted in rare crashes and deadlocks.

Fixes #4493
Closes #4494

PiperOrigin-RevId: 621619768
Change-Id: I66f00d8f0f3c37f9937c6d13890f7fa10038256d
This commit is contained in:
Derek Mauro 2024-04-03 13:21:06 -07:00 committed by Copybara-Service
parent ec7b38672c
commit d3a29ff624
1 changed files with 25 additions and 10 deletions
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35
googletest/src/gtest-port.cc
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@ -587,9 +587,11 @@ class ThreadLocalRegistryImpl {
// thread's ID. // thread's ID.
typedef std::map<DWORD, ThreadLocalValues> ThreadIdToThreadLocals; typedef std::map<DWORD, ThreadLocalValues> ThreadIdToThreadLocals;
// Holds the thread id and thread handle that we pass from struct WatcherThreadParams {
// StartWatcherThreadFor to WatcherThreadFunc. DWORD thread_id;
typedef std::pair<DWORD, HANDLE> ThreadIdAndHandle; HANDLE handle;
Notification has_initialized;
};
static void StartWatcherThreadFor(DWORD thread_id) { static void StartWatcherThreadFor(DWORD thread_id) {
// The returned handle will be kept in thread_map and closed by // The returned handle will be kept in thread_map and closed by
@ -597,6 +599,11 @@ class ThreadLocalRegistryImpl {
HANDLE thread = HANDLE thread =
::OpenThread(SYNCHRONIZE | THREAD_QUERY_INFORMATION, FALSE, thread_id); ::OpenThread(SYNCHRONIZE | THREAD_QUERY_INFORMATION, FALSE, thread_id);
GTEST_CHECK_(thread != nullptr); GTEST_CHECK_(thread != nullptr);
WatcherThreadParams* watcher_thread_params = new WatcherThreadParams;
watcher_thread_params->thread_id = thread_id;
watcher_thread_params->handle = thread;
// We need to pass a valid thread ID pointer into CreateThread for it // We need to pass a valid thread ID pointer into CreateThread for it
// to work correctly under Win98. // to work correctly under Win98.
DWORD watcher_thread_id; DWORD watcher_thread_id;
@ -604,7 +611,7 @@ class ThreadLocalRegistryImpl {
nullptr, // Default security. nullptr, // Default security.
0, // Default stack size 0, // Default stack size
&ThreadLocalRegistryImpl::WatcherThreadFunc, &ThreadLocalRegistryImpl::WatcherThreadFunc,
reinterpret_cast<LPVOID>(new ThreadIdAndHandle(thread_id, thread)), reinterpret_cast<LPVOID>(watcher_thread_params),
CREATE_SUSPENDED, &watcher_thread_id); CREATE_SUSPENDED, &watcher_thread_id);
GTEST_CHECK_(watcher_thread != nullptr) GTEST_CHECK_(watcher_thread != nullptr)
<< "CreateThread failed with error " << ::GetLastError() << "."; << "CreateThread failed with error " << ::GetLastError() << ".";
@ -614,17 +621,25 @@ class ThreadLocalRegistryImpl {
::GetThreadPriority(::GetCurrentThread())); ::GetThreadPriority(::GetCurrentThread()));
::ResumeThread(watcher_thread); ::ResumeThread(watcher_thread);
::CloseHandle(watcher_thread); ::CloseHandle(watcher_thread);
// Wait for the watcher thread to start to avoid race conditions.
// One specific race condition that can happen is that we have returned
// from main and have started to tear down, the newly spawned watcher
// thread may access already-freed variables, like global shared_ptrs.
watcher_thread_params->has_initialized.WaitForNotification();
} }
// Monitors exit from a given thread and notifies those // Monitors exit from a given thread and notifies those
// ThreadIdToThreadLocals about thread termination. // ThreadIdToThreadLocals about thread termination.
static DWORD WINAPI WatcherThreadFunc(LPVOID param) { static DWORD WINAPI WatcherThreadFunc(LPVOID param) {
const ThreadIdAndHandle* tah = WatcherThreadParams* watcher_thread_params =
reinterpret_cast<const ThreadIdAndHandle*>(param); reinterpret_cast<WatcherThreadParams*>(param);
GTEST_CHECK_(::WaitForSingleObject(tah->second, INFINITE) == WAIT_OBJECT_0); watcher_thread_params->has_initialized.Notify();
OnThreadExit(tah->first); GTEST_CHECK_(::WaitForSingleObject(watcher_thread_params->handle,
::CloseHandle(tah->second); INFINITE) == WAIT_OBJECT_0);
delete tah; OnThreadExit(watcher_thread_params->thread_id);
::CloseHandle(watcher_thread_params->handle);
delete watcher_thread_params;
return 0; return 0;
} }