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1 : //===--- CrashRecoveryContext.h - Crash Recovery ----------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 :
10 : #ifndef LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
11 : #define LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
12 :
13 : #include "llvm/ADT/STLExtras.h"
14 :
15 : namespace llvm {
16 : class CrashRecoveryContextCleanup;
17 :
18 : /// Crash recovery helper object.
19 : ///
20 : /// This class implements support for running operations in a safe context so
21 : /// that crashes (memory errors, stack overflow, assertion violations) can be
22 : /// detected and control restored to the crashing thread. Crash detection is
23 : /// purely "best effort", the exact set of failures which can be recovered from
24 : /// is platform dependent.
25 : ///
26 : /// Clients make use of this code by first calling
27 : /// CrashRecoveryContext::Enable(), and then executing unsafe operations via a
28 : /// CrashRecoveryContext object. For example:
29 : ///
30 : /// \code
31 : /// void actual_work(void *);
32 : ///
33 : /// void foo() {
34 : /// CrashRecoveryContext CRC;
35 : ///
36 : /// if (!CRC.RunSafely(actual_work, 0)) {
37 : /// ... a crash was detected, report error to user ...
38 : /// }
39 : ///
40 : /// ... no crash was detected ...
41 : /// }
42 : /// \endcode
43 : ///
44 : /// To assist recovery the class allows specifying set of actions that will be
45 : /// executed in any case, whether crash occurs or not. These actions may be used
46 : /// to reclaim resources in the case of crash.
47 : class CrashRecoveryContext {
48 : void *Impl;
49 : CrashRecoveryContextCleanup *head;
50 :
51 : public:
52 3792 : CrashRecoveryContext() : Impl(nullptr), head(nullptr) {}
53 : ~CrashRecoveryContext();
54 :
55 : /// Register cleanup handler, which is used when the recovery context is
56 : /// finished.
57 : /// The recovery context owns the handler.
58 : void registerCleanup(CrashRecoveryContextCleanup *cleanup);
59 :
60 : void unregisterCleanup(CrashRecoveryContextCleanup *cleanup);
61 :
62 : /// Enable crash recovery.
63 : static void Enable();
64 :
65 : /// Disable crash recovery.
66 : static void Disable();
67 :
68 : /// Return the active context, if the code is currently executing in a
69 : /// thread which is in a protected context.
70 : static CrashRecoveryContext *GetCurrent();
71 :
72 : /// Return true if the current thread is recovering from a crash.
73 : static bool isRecoveringFromCrash();
74 :
75 : /// Execute the provided callback function (with the given arguments) in
76 : /// a protected context.
77 : ///
78 : /// \return True if the function completed successfully, and false if the
79 : /// function crashed (or HandleCrash was called explicitly). Clients should
80 : /// make as little assumptions as possible about the program state when
81 : /// RunSafely has returned false.
82 : bool RunSafely(function_ref<void()> Fn);
83 : bool RunSafely(void (*Fn)(void*), void *UserData) {
84 : return RunSafely([&]() { Fn(UserData); });
85 : }
86 :
87 : /// Execute the provide callback function (with the given arguments) in
88 : /// a protected context which is run in another thread (optionally with a
89 : /// requested stack size).
90 : ///
91 : /// See RunSafely() and llvm_execute_on_thread().
92 : ///
93 : /// On Darwin, if PRIO_DARWIN_BG is set on the calling thread, it will be
94 : /// propagated to the new thread as well.
95 : bool RunSafelyOnThread(function_ref<void()>, unsigned RequestedStackSize = 0);
96 : bool RunSafelyOnThread(void (*Fn)(void*), void *UserData,
97 : unsigned RequestedStackSize = 0) {
98 : return RunSafelyOnThread([&]() { Fn(UserData); }, RequestedStackSize);
99 : }
100 :
101 : /// Explicitly trigger a crash recovery in the current process, and
102 : /// return failure from RunSafely(). This function does not return.
103 : void HandleCrash();
104 : };
105 :
106 : /// Abstract base class of cleanup handlers.
107 : ///
108 : /// Derived classes override method recoverResources, which makes actual work on
109 : /// resource recovery.
110 : ///
111 : /// Cleanup handlers are stored in a double list, which is owned and managed by
112 : /// a crash recovery context.
113 : class CrashRecoveryContextCleanup {
114 : protected:
115 : CrashRecoveryContext *context;
116 : CrashRecoveryContextCleanup(CrashRecoveryContext *context)
117 11691 : : context(context), cleanupFired(false) {}
118 :
119 : public:
120 : bool cleanupFired;
121 :
122 : virtual ~CrashRecoveryContextCleanup();
123 : virtual void recoverResources() = 0;
124 :
125 0 : CrashRecoveryContext *getContext() const {
126 0 : return context;
127 : }
128 :
129 : private:
130 : friend class CrashRecoveryContext;
131 : CrashRecoveryContextCleanup *prev, *next;
132 : };
133 :
134 : /// Base class of cleanup handler that controls recovery of resources of the
135 : /// given type.
136 : ///
137 : /// \tparam Derived Class that uses this class as a base.
138 : /// \tparam T Type of controlled resource.
139 : ///
140 : /// This class serves as a base for its template parameter as implied by
141 : /// Curiously Recurring Template Pattern.
142 : ///
143 : /// This class factors out creation of a cleanup handler. The latter requires
144 : /// knowledge of the current recovery context, which is provided by this class.
145 : template<typename Derived, typename T>
146 : class CrashRecoveryContextCleanupBase : public CrashRecoveryContextCleanup {
147 : protected:
148 : T *resource;
149 11689 : CrashRecoveryContextCleanupBase(CrashRecoveryContext *context, T *resource)
150 9105 : : CrashRecoveryContextCleanup(context), resource(resource) {}
151 :
152 : public:
153 : /// Creates cleanup handler.
154 : /// \param x Pointer to the resource recovered by this handler.
155 : /// \return New handler or null if the method was called outside a recovery
156 : /// context.
157 93406 : static Derived *create(T *x) {
158 93406 : if (x) {
159 81001 : if (CrashRecoveryContext *context = CrashRecoveryContext::GetCurrent())
160 11689 : return new Derived(context, x);
161 : }
162 : return nullptr;
163 : }
164 40504 : };
165 40504 :
166 37854 : /// Cleanup handler that reclaims resource by calling destructor on it.
167 3563 : template <typename T>
168 : class CrashRecoveryContextDestructorCleanup : public
169 : CrashRecoveryContextCleanupBase<CrashRecoveryContextDestructorCleanup<T>, T> {
170 : public:
171 42294 : CrashRecoveryContextDestructorCleanup(CrashRecoveryContext *context,
172 42294 : T *resource)
173 32573 : : CrashRecoveryContextCleanupBase<
174 3520 : CrashRecoveryContextDestructorCleanup<T>, T>(context, resource) {}
175 :
176 : virtual void recoverResources() {
177 : this->resource->~T();
178 5423 : }
179 5423 : };
180 5423 :
181 3452 : /// Cleanup handler that reclaims resource by calling 'delete' on it.
182 : template <typename T>
183 : class CrashRecoveryContextDeleteCleanup : public
184 : CrashRecoveryContextCleanupBase<CrashRecoveryContextDeleteCleanup<T>, T> {
185 2046 : public:
186 2046 : CrashRecoveryContextDeleteCleanup(CrashRecoveryContext *context, T *resource)
187 2046 : : CrashRecoveryContextCleanupBase<
188 144 : CrashRecoveryContextDeleteCleanup<T>, T>(context, resource) {}
189 :
190 0 : void recoverResources() override { delete this->resource; }
191 : };
192 2991 :
193 2991 : /// Cleanup handler that reclaims resource by calling its method 'Release'.
194 2957 : template <typename T>
195 976 : class CrashRecoveryContextReleaseRefCleanup : public
196 : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>, T> {
197 : public:
198 : CrashRecoveryContextReleaseRefCleanup(CrashRecoveryContext *context,
199 34 : T *resource)
200 34 : : CrashRecoveryContextCleanupBase<CrashRecoveryContextReleaseRefCleanup<T>,
201 34 : T>(context, resource) {}
202 34 :
203 : void recoverResources() override { this->resource->Release(); }
204 : };
205 :
206 : /// Helper class for managing resource cleanups.
207 : ///
208 : /// \tparam T Type of resource been reclaimed.
209 5269 : /// \tparam Cleanup Class that defines how the resource is reclaimed.
210 : ///
211 35 : /// Clients create objects of this type in the code executed in a crash recovery
212 : /// context to ensure that the resource will be reclaimed even in the case of
213 : /// crash. For example:
214 : ///
215 : /// \code
216 34 : /// void actual_work(void *) {
217 : /// ...
218 0 : /// std::unique_ptr<Resource> R(new Resource());
219 0 : /// CrashRecoveryContextCleanupRegistrar D(R.get());
220 0 : /// ...
221 : /// }
222 942 : ///
223 5164 : /// void foo() {
224 7 : /// CrashRecoveryContext CRC;
225 26 : ///
226 : /// if (!CRC.RunSafely(actual_work, 0)) {
227 : /// ... a crash was detected, report error to user ...
228 : /// }
229 : /// \endcode
230 136 : ///
231 : /// If the code of `actual_work` in the example above does not crash, the
232 0 : /// destructor of CrashRecoveryContextCleanupRegistrar removes cleanup code from
233 : /// the current CrashRecoveryContext and the resource is reclaimed by the
234 : /// destructor of std::unique_ptr. If crash happens, destructors are not called
235 : /// and the resource is reclaimed by cleanup object registered in the recovery
236 34 : /// context by the constructor of CrashRecoveryContextCleanupRegistrar.
237 : template <typename T, typename Cleanup = CrashRecoveryContextDeleteCleanup<T> >
238 0 : class CrashRecoveryContextCleanupRegistrar {
239 : CrashRecoveryContextCleanup *cleanup;
240 :
241 : public:
242 114 : CrashRecoveryContextCleanupRegistrar(T *x)
243 148 : : cleanup(Cleanup::create(x)) {
244 114 : if (cleanup)
245 76 : cleanup->getContext()->registerCleanup(cleanup);
246 114 : }
247 :
248 114 : ~CrashRecoveryContextCleanupRegistrar() { unregister(); }
249 :
250 0 : void unregister() {
251 0 : if (cleanup && !cleanup->cleanupFired)
252 0 : cleanup->getContext()->unregisterCleanup(cleanup);
253 0 : cleanup = nullptr;
254 0 : }
255 : };
256 : } // end namespace llvm
257 :
258 : #endif // LLVM_SUPPORT_CRASHRECOVERYCONTEXT_H
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