1 files changed, 73 insertions, 0 deletions
diff --git a/compiler-rt/lib/scudo/standalone/mutex.h b/compiler-rt/lib/scudo/standalone/mutex.h
new file mode 100644
index 000000000000..b26b2df06627
--- /dev/null
+++ b/compiler-rt/lib/scudo/standalone/mutex.h
@@ -0,0 +1,73 @@
+//===-- mutex.h -------------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SCUDO_MUTEX_H_
+#define SCUDO_MUTEX_H_
+
+#include "atomic_helpers.h"
+#include "common.h"
+
+#include <string.h>
+
+#if SCUDO_FUCHSIA
+#include <lib/sync/mutex.h> // for sync_mutex_t
+#endif
+
+namespace scudo {
+
+class HybridMutex {
+public:
+  void init() { memset(this, 0, sizeof(*this)); }
+  bool tryLock();
+  NOINLINE void lock() {
+    if (LIKELY(tryLock()))
+      return;
+      // The compiler may try to fully unroll the loop, ending up in a
+      // NumberOfTries*NumberOfYields block of pauses mixed with tryLocks. This
+      // is large, ugly and unneeded, a compact loop is better for our purpose
+      // here. Use a pragma to tell the compiler not to unroll the loop.
+#ifdef __clang__
+#pragma nounroll
+#endif
+    for (u8 I = 0U; I < NumberOfTries; I++) {
+      yieldProcessor(NumberOfYields);
+      if (tryLock())
+        return;
+    }
+    lockSlow();
+  }
+  void unlock();
+
+private:
+  static constexpr u8 NumberOfTries = 8U;
+  static constexpr u8 NumberOfYields = 8U;
+
+#if SCUDO_LINUX
+  atomic_u32 M;
+#elif SCUDO_FUCHSIA
+  sync_mutex_t M;
+#endif
+
+  void lockSlow();
+};
+
+class ScopedLock {
+public:
+  explicit ScopedLock(HybridMutex &M) : Mutex(M) { Mutex.lock(); }
+  ~ScopedLock() { Mutex.unlock(); }
+
+private:
+  HybridMutex &Mutex;
+
+  ScopedLock(const ScopedLock &) = delete;
+  void operator=(const ScopedLock &) = delete;
+};
+
+} // namespace scudo
+
+#endif // SCUDO_MUTEX_H_