[PATCH] D40583: Defer StartBackgroundThread() and StopBackgroundThread() in TSan

[Kamil Rytarowski via Phabricator via llvm-commits]

krytarowski updated this revision to Diff 124660.
krytarowski added a comment.

Try to make the code prettier.


Repository:
  rL LLVM

https://reviews.llvm.org/D40583

Files:
  lib/tsan/rtl/tsan_interceptors.cc
  lib/tsan/rtl/tsan_rtl.cc
  lib/tsan/rtl/tsan_rtl.h


Index: lib/tsan/rtl/tsan_rtl.h
===================================================================
--- lib/tsan/rtl/tsan_rtl.h
+++ lib/tsan/rtl/tsan_rtl.h
@@ -700,6 +700,7 @@
 void PrintCurrentStackSlow(uptr pc);  // uses libunwind
 
 void Initialize(ThreadState *thr);
+void TSanMaybeSpawnBackgroundThread();
 int Finalize(ThreadState *thr);
 
 void OnUserAlloc(ThreadState *thr, uptr pc, uptr p, uptr sz, bool write);
Index: lib/tsan/rtl/tsan_rtl.cc
===================================================================
--- lib/tsan/rtl/tsan_rtl.cc
+++ lib/tsan/rtl/tsan_rtl.cc
@@ -384,13 +384,6 @@
 #if !SANITIZER_GO
   InitializeLibIgnore();
   Symbolizer::GetOrInit()->AddHooks(EnterSymbolizer, ExitSymbolizer);
-  // On MIPS, TSan initialization is run before
-  // __pthread_initialize_minimal_internal() is finished, so we can not spawn
-  // new threads.
-#ifndef __mips__
-  StartBackgroundThread();
-  SetSandboxingCallback(StopBackgroundThread);
-#endif
 #endif
 
   VPrintf(1, "***** Running under ThreadSanitizer v2 (pid %d) *****\n",
@@ -419,6 +412,24 @@
   OnInitialize();
 }
 
+void TSanMaybeSpawnBackgroundThread() {
+  // On MIPS, TSan initialization is run before
+  // __pthread_initialize_minimal_internal() is finished, so we can not spawn
+  // new threads.
+#if !SANITIZER_GO && !defined(__mips__)
+  static atomic_uint32_t bg_thread = {};
+  u32 cond = atomic_load(&bg_thread, memory_order_acquire);
+  if (cond == 0) {
+    if (atomic_compare_exchange_strong(&bg_thread, &cond, 1,
+                                       memory_order_acq_rel)) {
+      StartBackgroundThread();
+      SetSandboxingCallback(StopBackgroundThread);
+    }
+  }
+#endif
+}
+
+
 int Finalize(ThreadState *thr) {
   bool failed = false;
 
Index: lib/tsan/rtl/tsan_interceptors.cc
===================================================================
--- lib/tsan/rtl/tsan_interceptors.cc
+++ lib/tsan/rtl/tsan_interceptors.cc
@@ -974,6 +974,9 @@
 TSAN_INTERCEPTOR(int, pthread_create,
     void *th, void *attr, void *(*callback)(void*), void * param) {
   SCOPED_INTERCEPTOR_RAW(pthread_create, th, attr, callback, param);
+
+  TSanMaybeSpawnBackgroundThread();
+
   if (ctx->after_multithreaded_fork) {
     if (flags()->die_after_fork) {
       Report("ThreadSanitizer: starting new threads after multi-threaded "


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