Don't call getenv in side threads (#984)

Summary:
Calling `getenv` on side threads is dangerous as it can potentially segfault if the main thread is in the middle of setting environment variables: pytorch/pytorch#134596

This PR only calls `getenv` only once during the first call of  `isDaemonEnvVarSet()`, which is called from `init`.

Pull Request resolved: #984

Reviewed By: sraikund16

Differential Revision: D62152169

Pulled By: malfet

fbshipit-source-id: 28dff07cb9775b004580749805b6437dba978eeb

Co-authored-by: Nikita Shulga <[email protected]>

Author: 2 people

libkineto/include/Config.h

@@ -502,4 +502,8 @@ class Config : public AbstractConfig {
 
 constexpr char kUseDaemonEnvVar[] = "KINETO_USE_DAEMON";
 
+#if __linux__
+bool isDaemonEnvVarSet();
+#endif
+
 } // namespace libkineto

libkineto/src/Config.cpp

@@ -243,10 +243,21 @@ Config::Config()
     factories->addFeatureConfigs(*this);
   }
 #if __linux__
-  enableIpcFabric_ = (getenv(kUseDaemonEnvVar) != nullptr);
+  enableIpcFabric_ = libkineto::isDaemonEnvVarSet();
 #endif
 }
 
+#if __linux__
+bool isDaemonEnvVarSet() {
+  static bool rc = [] {
+      void *ptr = getenv(kUseDaemonEnvVar);
+      return ptr != nullptr;
+  }();
+  return rc;
+}
+#endif
+
+
 std::shared_ptr<void> Config::getStaticObjectsLifetimeHandle() {
   return configFactories();
 }

libkineto/src/init.cpp

@@ -131,7 +131,7 @@ void libkineto_init(bool cpuOnly, bool logOnError) {
 
   // Factory to connect to open source daemon if present
 #if __linux__
-  if (getenv(kUseDaemonEnvVar) != nullptr) {
+  if (libkineto::isDaemonEnvVarSet()) {
     LOG(INFO) << "Registering daemon config loader, cpuOnly =  "
               << cpuOnly;
     DaemonConfigLoader::registerFactory();