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1//===-- xray_recursion_guard.h ---------------------------------*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file is a part of XRay, a dynamic runtime instrumentation system.10//11//===----------------------------------------------------------------------===//12#ifndef XRAY_XRAY_RECURSION_GUARD_H13#define XRAY_XRAY_RECURSION_GUARD_H14 15#include "sanitizer_common/sanitizer_atomic.h"16 17namespace __xray {18 19/// The RecursionGuard is useful for guarding against signal handlers which are20/// also potentially calling XRay-instrumented functions. To use the21/// RecursionGuard, you'll typically need a thread_local atomic_uint8_t:22///23/// thread_local atomic_uint8_t Guard{0};24///25/// // In a handler function:26/// void handleArg0(int32_t F, XRayEntryType T) {27/// RecursionGuard G(Guard);28/// if (!G)29/// return; // Failed to acquire the guard.30/// ...31/// }32///33class RecursionGuard {34 atomic_uint8_t &Running;35 const bool Valid;36 37public:38 explicit inline RecursionGuard(atomic_uint8_t &R)39 : Running(R), Valid(!atomic_exchange(&R, 1, memory_order_acq_rel)) {}40 41 inline RecursionGuard(const RecursionGuard &) = delete;42 inline RecursionGuard(RecursionGuard &&) = delete;43 inline RecursionGuard &operator=(const RecursionGuard &) = delete;44 inline RecursionGuard &operator=(RecursionGuard &&) = delete;45 46 explicit inline operator bool() const { return Valid; }47 48 inline ~RecursionGuard() noexcept {49 if (Valid)50 atomic_store(&Running, 0, memory_order_release);51 }52};53 54} // namespace __xray55 56#endif // XRAY_XRAY_RECURSION_GUARD_H57