diff options
Diffstat (limited to 'lib/xray/xray_recursion_guard.h')
-rw-r--r-- | lib/xray/xray_recursion_guard.h | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/lib/xray/xray_recursion_guard.h b/lib/xray/xray_recursion_guard.h new file mode 100644 index 000000000000..6edadea563bc --- /dev/null +++ b/lib/xray/xray_recursion_guard.h @@ -0,0 +1,57 @@ +//===-- xray_recursion_guard.h ---------------------------------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// 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 |