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| 1 | //===---- ExclusiveAccess.h - Helper for exclusive access data structures -===// |
|---|---|
| 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-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | // |
| 9 | //===----------------------------------------------------------------------===// |
| 10 | |
| 11 | #ifndef OMPTARGET_EXCLUSIVE_ACCESS |
| 12 | #define OMPTARGET_EXCLUSIVE_ACCESS |
| 13 | |
| 14 | #include <cassert> |
| 15 | #include <cstddef> |
| 16 | #include <cstdint> |
| 17 | #include <mutex> |
| 18 | |
| 19 | /// Forward declaration. |
| 20 | template <typename Ty> struct Accessor; |
| 21 | |
| 22 | /// A protected object is a simple wrapper to allocate an object of type \p Ty |
| 23 | /// together with a mutex that guards accesses to the object. The only way to |
| 24 | /// access the object is through the "exclusive accessor" which will lock the |
| 25 | /// mutex accordingly. |
| 26 | template <typename Ty> struct ProtectedObj { |
| 27 | using AccessorTy = Accessor<Ty>; |
| 28 | |
| 29 | /// Get an exclusive access Accessor object. \p DoNotGetAccess allows to |
| 30 | /// create an accessor that is not owning anything based on a boolean |
| 31 | /// condition. |
| 32 | AccessorTy getExclusiveAccessor(bool DoNotGetAccess = false); |
| 33 | |
| 34 | private: |
| 35 | Ty Obj; |
| 36 | std::mutex Mtx; |
| 37 | friend struct Accessor<Ty>; |
| 38 | }; |
| 39 | |
| 40 | /// Helper to provide transparent exclusive access to protected objects. |
| 41 | template <typename Ty> struct Accessor { |
| 42 | /// Default constructor does not own anything and cannot access anything. |
| 43 | Accessor() : Ptr(nullptr) {} |
| 44 | |
| 45 | /// Constructor to get exclusive access by locking the mutex protecting the |
| 46 | /// underlying object. |
| 47 | Accessor(ProtectedObj<Ty> &PO) : Ptr(&PO) { lock(); } |
| 48 | |
| 49 | /// Constructor to get exclusive access by taking it from \p Other. |
| 50 | Accessor(Accessor<Ty> &&Other) : Ptr(Other.Ptr) { Other.Ptr = nullptr; } |
| 51 | |
| 52 | Accessor(Accessor &Other) = delete; |
| 53 | |
| 54 | /// If the object is still owned when the lifetime ends we give up access. |
| 55 | ~Accessor() { unlock(); } |
| 56 | |
| 57 | /// Give up access to the underlying object, virtually "destroying" the |
| 58 | /// accessor even if the object is still life. |
| 59 | void destroy() { |
| 60 | unlock(); |
| 61 | Ptr = nullptr; |
| 62 | } |
| 63 | |
| 64 | /// Provide transparent access to the underlying object. |
| 65 | Ty &operator*() { |
| 66 | assert(Ptr && "Trying to access an object through a non-owning (or " |
| 67 | "destroyed) accessor!"); |
| 68 | return Ptr->Obj; |
| 69 | } |
| 70 | Ty *operator->() { |
| 71 | assert(Ptr && "Trying to access an object through a non-owning (or " |
| 72 | "destroyed) accessor!"); |
| 73 | return &Ptr->Obj; |
| 74 | } |
| 75 | |
| 76 | private: |
| 77 | /// Lock the underlying object if there is one. |
| 78 | void lock() { |
| 79 | if (Ptr) |
| 80 | Ptr->Mtx.lock(); |
| 81 | } |
| 82 | |
| 83 | /// Unlock the underlying object if there is one. |
| 84 | void unlock() { |
| 85 | if (Ptr) |
| 86 | Ptr->Mtx.unlock(); |
| 87 | } |
| 88 | |
| 89 | /// Pointer to the underlying object or null if the accessor lost access, |
| 90 | /// e.g., after a destroy call. |
| 91 | ProtectedObj<Ty> *Ptr; |
| 92 | }; |
| 93 | |
| 94 | template <typename Ty> |
| 95 | Accessor<Ty> ProtectedObj<Ty>::getExclusiveAccessor(bool DoNotGetAccess) { |
| 96 | if (DoNotGetAccess) |
| 97 | return Accessor<Ty>(); |
| 98 | return Accessor<Ty>(*this); |
| 99 | } |
| 100 | |
| 101 | #endif |
| 102 |
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