[tsan] Summary should point to "responsible caller" for external races

[kubamracek]

Summary

For TSan "external" races, the bug is in the caller of the API, not the function itself. This patch makes sure that the "SUMMARY:" line of TSan reports print out the name of the responsible caller.

[dvyukov]

lib/tsan/rtl/tsan_report.cc

384

This conflicts with D31630.
rep->typ == ReportTypeExternalRace can be, but this stack may not be an external access.
Let's first land D31630 and then get back to this.

lib/tsan/rtl/tsan_report.cc

void PrintReport(const ReportDesc *rep) {
 
   for (uptr i = 0; i < rep->threads.Size(); i++)
     PrintThread(rep->threads[i]);
 
   if (rep->typ == ReportTypeThreadLeak && rep->count > 1)
     Printf("  And %d more similar thread leaks.\n\n", rep->count - 1);
 
   if (ReportStack *stack = ChooseSummaryStack(rep)) {
-    if (SymbolizedStack *frame = SkipTsanInternalFrames(stack->frames))
+    if (SymbolizedStack *frame = SkipTsanInternalFrames(stack->frames)) {
+      if (rep->typ == ReportTypeExternalRace) {
+        // For external races, the responsible frame is 2nd from the top
+        frame = frame->next;
+      }
+      if (frame)
         ReportErrorSummary(rep_typ_str, frame->info);
     }
+  }
 
   if (common_flags()->print_module_map == 2) PrintModuleMap();
 
   Printf("==================\n");
 }
 
 #else  // #if !SANITIZER_GO
 

test/tsan/Darwin/external.cc

 #if defined(USE_TSAN_CALLBACKS)
   callback_write(ref, __builtin_return_address(0), tag);
 #endif
   ref->_another = val;
 }
 
 #else  // defined(SHARED_LIB)
 
+void UserCodeRead(MyObjectRef ref) {
+  ObjectRead(ref);
+}
+
+void UserCodeWrite(MyObjectRef ref, long val) {
+  ObjectWrite(ref, val);
+}
+
+void UserCodeWriteAnother(MyObjectRef ref, long val) {
+  ObjectWriteAnother(ref, val);
+}
+
 int main(int argc, char *argv[]) {
   InitializeLibrary();
   
   {
     MyObjectRef ref = ObjectCreate();
-    std::thread t1([ref]{ ObjectRead(ref); });
-    std::thread t2([ref]{ ObjectRead(ref); });
+    std::thread t1([ref]{ UserCodeRead(ref); });
+    std::thread t2([ref]{ UserCodeRead(ref); });
     t1.join();
     t2.join();
   }
   
   // CHECK-NOT: WARNING: ThreadSanitizer
   
   fprintf(stderr, "RR test done\n");
   // CHECK: RR test done
 
   {
     MyObjectRef ref = ObjectCreate();
-    std::thread t1([ref]{ ObjectRead(ref); });
-    std::thread t2([ref]{ ObjectWrite(ref, 66); });
+    std::thread t1([ref]{ UserCodeRead(ref); });
+    std::thread t2([ref]{ UserCodeWrite(ref, 66); });
     t1.join();
     t2.join();
   }
   
   // TEST1: WARNING: ThreadSanitizer: data race
   // TEST1: {{Write|Read}} of size 8 at
   // TEST1: Previous {{write|read}} of size 8 at
   // TEST1: Location is heap block of size 16 at
   
   // TEST2-NOT: WARNING: ThreadSanitizer
   
   // TEST3: WARNING: ThreadSanitizer: race on a library object
   // TEST3: {{Mutating|read-only}} access of object MyLibrary::MyObject at
-  // TEST3: {{ObjectWrite|ObjectRead}}
+  // TEST3: {{UserCodeWrite|UserCodeRead}}
   // TEST3: Previous {{mutating|read-only}} access of object MyLibrary::MyObject at
-  // TEST3: {{ObjectWrite|ObjectRead}}
+  // TEST3: {{UserCodeWrite|UserCodeRead}}
   // TEST3: Location is MyLibrary::MyObject object of size 16 at
   // TEST3: {{ObjectCreate}}
+  // TEST3: SUMMARY: ThreadSanitizer: race on a library object {{.*}}external.cc{{.*}}{{UserCodeWrite|UserCodeRead}}
 
   fprintf(stderr, "RW test done\n");
   // CHECK: RW test done
 
   {
     MyObjectRef ref = ObjectCreate();
-    std::thread t1([ref]{ ObjectWrite(ref, 76); });
-    std::thread t2([ref]{ ObjectWriteAnother(ref, 77); });
+    std::thread t1([ref]{ UserCodeWrite(ref, 76); });
+    std::thread t2([ref]{ UserCodeWriteAnother(ref, 77); });
     t1.join();
     t2.join();
   }
   
   // TEST1-NOT: WARNING: ThreadSanitizer: data race
   
   // TEST2-NOT: WARNING: ThreadSanitizer
   
   // TEST3: WARNING: ThreadSanitizer: race on a library object
   // TEST3: Mutating access of object MyLibrary::MyObject at
-  // TEST3: {{ObjectWrite|ObjectWriteAnother}}
+  // TEST3: {{UserCodeWrite|UserCodeWriteAnother}}
   // TEST3: Previous mutating access of object MyLibrary::MyObject at
-  // TEST3: {{ObjectWrite|ObjectWriteAnother}}
+  // TEST3: {{UserCodeWrite|UserCodeWriteAnother}}
   // TEST3: Location is MyLibrary::MyObject object of size 16 at
   // TEST3: {{ObjectCreate}}
+  // TEST3: SUMMARY: ThreadSanitizer: race on a library object {{.*}}external.cc{{.*}}{{UserCodeWrite|UserCodeWriteAnother}}
 
   fprintf(stderr, "WW test done\n");
   // CHECK: WW test done
 }
 
 #endif  // defined(SHARED_LIB)