forked from OSchip/llvm-project
58 lines
1.8 KiB
C++
58 lines
1.8 KiB
C++
//===-- xray_recursion_guard.h ---------------------------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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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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