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//===-- xray_recursion_guard.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
//
//===----------------------------------------------------------------------===//
//
// This file is a part of XRay, a dynamic runtime instrumentation system.
//
//===----------------------------------------------------------------------===//
#ifndef XRAY_XRAY_RECURSION_GUARD_H
#define XRAY_XRAY_RECURSION_GUARD_H
#include "sanitizer_common/sanitizer_atomic.h"
namespace __xray {
/// The RecursionGuard is useful for guarding against signal handlers which are
/// also potentially calling XRay-instrumented functions. To use the
/// RecursionGuard, you'll typically need a thread_local atomic_uint8_t:
///
/// thread_local atomic_uint8_t Guard{0};
///
/// // In a handler function:
/// void handleArg0(int32_t F, XRayEntryType T) {
/// RecursionGuard G(Guard);
/// if (!G)
/// return; // Failed to acquire the guard.
/// ...
/// }
///
class RecursionGuard {
atomic_uint8_t &Running;
const bool Valid;
public:
explicit inline RecursionGuard(atomic_uint8_t &R)
: Running(R), Valid(!atomic_exchange(&R, 1, memory_order_acq_rel)) {}
inline RecursionGuard(const RecursionGuard &) = delete;
inline RecursionGuard(RecursionGuard &&) = delete;
inline RecursionGuard &operator=(const RecursionGuard &) = delete;
inline RecursionGuard &operator=(RecursionGuard &&) = delete;
explicit inline operator bool() const { return Valid; }
inline ~RecursionGuard() noexcept {
if (Valid)
atomic_store(&Running, 0, memory_order_release);
}
};
} // namespace __xray
#endif // XRAY_XRAY_RECURSION_GUARD_H
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