[Fuzzer] Assign names to workers

Allow to have a name for workers in case the fuzzed code is itself using threads.

Reviewers: vitalybuka

Reviewed-By: vitalybuka

Differential Revision: https://reviews.llvm.org/D155754

compiler-rt/lib/fuzzer/FuzzerCommand.h

@@ -19,6 +19,7 @@
 #include <sstream>
 #include <string>
 #include <vector>
+#include <thread>
 
 namespace fuzzer {
 

compiler-rt/lib/fuzzer/FuzzerDriver.cpp

@@ -293,9 +293,12 @@ static int RunInMultipleProcesses(const std::vector<std::string> &Args,
   std::vector<std::thread> V;
   std::thread Pulse(PulseThread);
   Pulse.detach();
-  for (unsigned i = 0; i < NumWorkers; i++)
-    V.push_back(std::thread(WorkerThread, std::ref(Cmd), &Counter, NumJobs,
-                            &HasErrors));
+  V.resize(NumWorkers);
+  for (unsigned i = 0; i < NumWorkers; i++) {
+    V[i] = std::thread(WorkerThread, std::ref(Cmd), &Counter, NumJobs,
+                            &HasErrors);
+    SetThreadName(V[i], "FuzzerWorker");
+  }
   for (auto &T : V)
     T.join();
   return HasErrors ? 1 : 0;

compiler-rt/lib/fuzzer/FuzzerUtil.h

@@ -59,6 +59,8 @@ size_t GetPeakRSSMb();
 int ExecuteCommand(const Command &Cmd);
 bool ExecuteCommand(const Command &Cmd, std::string *CmdOutput);
 
+void SetThreadName(std::thread &thread, const std::string &name);
+
 // Fuchsia does not have popen/pclose.
 FILE *OpenProcessPipe(const char *Command, const char *Mode);
 int CloseProcessPipe(FILE *F);

compiler-rt/lib/fuzzer/FuzzerUtilDarwin.cpp

@@ -165,6 +165,11 @@ void DiscardOutput(int Fd) {
   fclose(Temp);
 }
 
+void SetThreadName(std::thread &thread, const std::string &name) {
+  // TODO ?
+  // Darwin allows to set the name only on the current thread it seems
+}
+
 } // namespace fuzzer
 
 #endif // LIBFUZZER_APPLE

compiler-rt/lib/fuzzer/FuzzerUtilFuchsia.cpp

@@ -605,6 +605,10 @@ size_t PageSize() {
   return PageSizeCached;
 }
 
+void SetThreadName(std::thread &thread, const std::string &name) {
+  // TODO ?
+}
+
 } // namespace fuzzer
 
 #endif // LIBFUZZER_FUCHSIA

compiler-rt/lib/fuzzer/FuzzerUtilLinux.cpp

@@ -40,6 +40,14 @@ void DiscardOutput(int Fd) {
   fclose(Temp);
 }
 
+void SetThreadName(std::thread &thread, const std::string &name) {
+#if LIBFUZZER_LINUX || LIBFUZZER_FREEBSD
+  (void)pthread_setname_np(thread.native_handle(), name.c_str());
+#elif LIBFUZZER_NETBSD
+  (void)pthread_set_name_np(thread.native_handle(), "%s", name.c_str());
+#endif
+}
+
 } // namespace fuzzer
 
 #endif

compiler-rt/lib/fuzzer/FuzzerUtilWindows.cpp

@@ -233,6 +233,11 @@ size_t PageSize() {
   return PageSizeCached;
 }
 
+void SetThreadName(std::thread &thread, const std::string &name) {
+  // TODO ?
+  // to UTF-8 then SetThreadDescription ?
+}
+
 } // namespace fuzzer
 
 #endif // LIBFUZZER_WINDOWS