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Fix SIGSEGV in Python stub on non-graceful (parent death) termination #446

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Fix SIGSEGV in Python stub on non-graceful (parent death) termination #446

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36 changes: 17 additions & 19 deletions src/pb_stub.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@
#include <windows.h>
#else
#include <sys/wait.h>
#include <unistd.h> // _exit
#endif

#ifdef TRITON_ENABLE_GPU
Expand All @@ -76,8 +77,6 @@ using cudaStream_t = void*;

namespace triton { namespace backend { namespace python {

std::atomic<bool> non_graceful_exit = {false};

void
SignalHandler(int signum)
{
Expand Down Expand Up @@ -2162,7 +2161,7 @@ main(int argc, char** argv)
#endif
std::atomic<bool> background_thread_running = {true};
std::thread background_thread =
std::thread([stub, &parent_pid, &background_thread_running, &logger] {
std::thread([stub, &parent_pid, &background_thread_running] {
// Send a dummy message after the stub process is launched to notify the
// parent process that the health thread has started.
std::unique_ptr<IPCMessage> ipc_message = IPCMessage::Create(
Expand All @@ -2179,23 +2178,22 @@ main(int argc, char** argv)
stub->UpdateHealth();

if (!ParentProcessActive(parent_pid)) {
// When unhealthy, we should stop attempting to send
// messages to the backend ASAP.
if (stub->StubToParentServiceActive()) {
stub->TerminateStubToParentQueueMonitor();
}
if (stub->ParentToStubServiceActive()) {
stub->TerminateParentToStubQueueMonitor();
}
// Destroy Stub
// The parent process (tritonserver) died abruptly (e.g. SIGKILL
// after the termination grace period, an OOM-kill, or a crash) and
// could not send a Finalize command. The RunCommand loop and the
// model instance threads are still operating on the shared memory
// region and its process-shared mutexes. Running the normal
// teardown from this background thread is unsafe: DestroyInstance()
// unmaps the region (~SharedMemoryManager -> ~mapped_region ->
// munmap), and exit() would unmap it as well via static
// destructors. Doing so while those threads are still using the
// region is a data race that faults them with SIGSEGV inside the
// shm mutex (SEGV_MAPERR on the lock word). Since the process is
// going away and the region is owned and reclaimed by the parent
// (the kernel reclaims all mappings on process exit), terminate
// immediately with _exit() so that no destructors run.
LOG_INFO << "Non-graceful termination detected. ";
background_thread_running = false;
non_graceful_exit = true;

// Destroy stub and exit.
logger.reset();
Stub::DestroyInstance();
exit(1);
_exit(1);
}
}
});
Expand Down