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to reflect the new license. We understand that people may be surprised that we're moving the header entirely to discuss the new license. We checked this carefully with the Foundation's lawyer and we believe this is the correct approach. Essentially, all code in the project is now made available by the LLVM project under our new license, so you will see that the license headers include that license only. Some of our contributors have contributed code under our old license, and accordingly, we have retained a copy of our old license notice in the top-level files in each project and repository. llvm-svn: 351636
57 lines
1.8 KiB
C++
57 lines
1.8 KiB
C++
//===-- xray_recursion_guard.h ---------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file is a part of XRay, a dynamic runtime instrumentation system.
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//
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//===----------------------------------------------------------------------===//
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#ifndef XRAY_XRAY_RECURSION_GUARD_H
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#define XRAY_XRAY_RECURSION_GUARD_H
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#include "sanitizer_common/sanitizer_atomic.h"
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namespace __xray {
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/// The RecursionGuard is useful for guarding against signal handlers which are
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/// also potentially calling XRay-instrumented functions. To use the
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/// RecursionGuard, you'll typically need a thread_local atomic_uint8_t:
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///
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/// thread_local atomic_uint8_t Guard{0};
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///
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/// // In a handler function:
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/// void handleArg0(int32_t F, XRayEntryType T) {
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/// RecursionGuard G(Guard);
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/// if (!G)
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/// return; // Failed to acquire the guard.
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/// ...
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/// }
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///
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class RecursionGuard {
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atomic_uint8_t &Running;
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const bool Valid;
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public:
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explicit inline RecursionGuard(atomic_uint8_t &R)
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: Running(R), Valid(!atomic_exchange(&R, 1, memory_order_acq_rel)) {}
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inline RecursionGuard(const RecursionGuard &) = delete;
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inline RecursionGuard(RecursionGuard &&) = delete;
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inline RecursionGuard &operator=(const RecursionGuard &) = delete;
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inline RecursionGuard &operator=(RecursionGuard &&) = delete;
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explicit inline operator bool() const { return Valid; }
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inline ~RecursionGuard() noexcept {
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if (Valid)
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atomic_store(&Running, 0, memory_order_release);
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}
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};
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} // namespace __xray
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#endif // XRAY_XRAY_RECURSION_GUARD_H
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