[TSAN] Add __tsan_check_no_mutexes_held helper

This adds a new helper that can be called from application code to ensure that no mutexes are held on specific code paths. This is useful for multiple scenarios, including ensuring no locks are held:

- at thread exit
- in peformance-critical code
- when a coroutine is suspended (can cause deadlocks)

See this discourse thread for more discussion:
https://discourse.llvm.org/t/add-threadsanitizer-check-to-prevent-coroutine-suspending-while-holding-a-lock-potential-deadlock/74051

This resubmits and fixes llvm#69372 (was reverted because of build breakage).
This also includes the followup change llvm#71471 (to fix a land race).

compiler-rt/include/sanitizer/tsan_interface.h

@@ -127,6 +127,10 @@ void SANITIZER_CDECL __tsan_mutex_post_signal(void *addr, unsigned flags);
 void SANITIZER_CDECL __tsan_mutex_pre_divert(void *addr, unsigned flags);
 void SANITIZER_CDECL __tsan_mutex_post_divert(void *addr, unsigned flags);
 
+// Check that the current thread does not hold any mutexes,
+// report a bug report otherwise.
+void SANITIZER_CDECL __tsan_check_no_mutexes_held();
+
 // External race detection API.
 // Can be used by non-instrumented libraries to detect when their objects are
 // being used in an unsafe manner.

compiler-rt/lib/tsan/rtl/tsan.syms.extra

@@ -22,6 +22,7 @@ __tsan_mutex_pre_signal
 __tsan_mutex_post_signal
 __tsan_mutex_pre_divert
 __tsan_mutex_post_divert
+__tsan_check_no_mutexes_held
 __tsan_get_current_fiber
 __tsan_create_fiber
 __tsan_destroy_fiber

compiler-rt/lib/tsan/rtl/tsan_debugging.cpp

@@ -35,7 +35,9 @@ static const char *ReportTypeDescription(ReportType typ) {
     case ReportTypeSignalUnsafe: return "signal-unsafe-call";
     case ReportTypeErrnoInSignal: return "errno-in-signal-handler";
     case ReportTypeDeadlock: return "lock-order-inversion";
-    // No default case so compiler warns us if we miss one
+    case ReportTypeMutexHeldWrongContext:
+      return "mutex-held-in-wrong-context";
+      // No default case so compiler warns us if we miss one
   }
   UNREACHABLE("missing case");
 }

compiler-rt/lib/tsan/rtl/tsan_interface_ann.cpp

@@ -435,4 +435,26 @@ void __tsan_mutex_post_divert(void *addr, unsigned flagz) {
   ThreadIgnoreBegin(thr, 0);
   ThreadIgnoreSyncBegin(thr, 0);
 }
+
+static void ReportMutexHeldWrongContext(ThreadState *thr, uptr pc) {
+  ThreadRegistryLock l(&ctx->thread_registry);
+  ScopedReport rep(ReportTypeMutexHeldWrongContext);
+  for (uptr i = 0; i < thr->mset.Size(); ++i) {
+    MutexSet::Desc desc = thr->mset.Get(i);
+    rep.AddMutex(desc.addr, desc.stack_id);
+  }
+  VarSizeStackTrace trace;
+  ObtainCurrentStack(thr, pc, &trace);
+  rep.AddStack(trace, true);
+  OutputReport(thr, rep);
+}
+
+INTERFACE_ATTRIBUTE
+void __tsan_check_no_mutexes_held() {
+  SCOPED_ANNOTATION(__tsan_check_no_mutexes_held);
+  if (thr->mset.Size() == 0) {
+    return;
+  }
+  ReportMutexHeldWrongContext(thr, pc);
+}
 }  // extern "C"

compiler-rt/lib/tsan/rtl/tsan_report.cpp

@@ -93,7 +93,9 @@ static const char *ReportTypeString(ReportType typ, uptr tag) {
       return "signal handler spoils errno";
     case ReportTypeDeadlock:
       return "lock-order-inversion (potential deadlock)";
-    // No default case so compiler warns us if we miss one
+    case ReportTypeMutexHeldWrongContext:
+      return "mutex held in the wrong context";
+      // No default case so compiler warns us if we miss one
   }
   UNREACHABLE("missing case");
 }

compiler-rt/lib/tsan/rtl/tsan_report.h

@@ -34,7 +34,8 @@ enum ReportType {
   ReportTypeMutexBadReadUnlock,
   ReportTypeSignalUnsafe,
   ReportTypeErrnoInSignal,
-  ReportTypeDeadlock
+  ReportTypeDeadlock,
+  ReportTypeMutexHeldWrongContext
 };
 
 struct ReportStack {

compiler-rt/lib/tsan/rtl/tsan_suppressions.cpp

@@ -81,6 +81,7 @@ static const char *conv(ReportType typ) {
     case ReportTypeMutexBadUnlock:
     case ReportTypeMutexBadReadLock:
     case ReportTypeMutexBadReadUnlock:
+    case ReportTypeMutexHeldWrongContext:
       return kSuppressionMutex;
     case ReportTypeSignalUnsafe:
     case ReportTypeErrnoInSignal:

compiler-rt/test/tsan/mutex_held_wrong_context.cpp

@@ -0,0 +1,34 @@
+// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
+#include "test.h"
+
+pthread_mutex_t mtx;
+
+__attribute__((noinline)) void Func1() {
+  pthread_mutex_lock(&mtx);
+  __tsan_check_no_mutexes_held();
+  pthread_mutex_unlock(&mtx);
+}
+
+__attribute__((noinline)) void Func2() {
+  pthread_mutex_lock(&mtx);
+  pthread_mutex_unlock(&mtx);
+  __tsan_check_no_mutexes_held();
+}
+
+int main() {
+  pthread_mutex_init(&mtx, NULL);
+  Func1();
+  Func2();
+  return 0;
+}
+
+// CHECK: WARNING: ThreadSanitizer: mutex held in the wrong context
+// CHECK:     {{.*}}__tsan_check_no_mutexes_held{{.*}}
+// CHECK:     {{.*}}Func1{{.*}}
+// CHECK:     {{.*}}main{{.*}}
+// CHECK:   Mutex {{.*}} created at:
+// CHECK:     {{.*}}pthread_mutex_init{{.*}}
+// CHECK:     {{.*}}main{{.*}}
+// CHECK: SUMMARY: ThreadSanitizer: mutex held in the wrong context {{.*}}mutex_held_wrong_context.cpp{{.*}}Func1
+
+// CHECK-NOT: SUMMARY: ThreadSanitizer: mutex held in the wrong context {{.*}}mutex_held_wrong_context.cpp{{.*}}Func2