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Diffstat (limited to 'base/threading/thread_collision_warner.h')
| -rw-r--r-- | base/threading/thread_collision_warner.h | 244 |
1 files changed, 244 insertions, 0 deletions
diff --git a/base/threading/thread_collision_warner.h b/base/threading/thread_collision_warner.h new file mode 100644 index 000000000000..4460602c6c40 --- /dev/null +++ b/base/threading/thread_collision_warner.h @@ -0,0 +1,244 @@ +// Copyright (c) 2011 The Chromium Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#ifndef BASE_THREADING_THREAD_COLLISION_WARNER_H_ +#define BASE_THREADING_THREAD_COLLISION_WARNER_H_ +#pragma once + +#include <memory> + +#include "base/base_export.h" +#include "base/atomicops.h" + +// A helper class alongside macros to be used to verify assumptions about thread +// safety of a class. +// +// Example: Queue implementation non thread-safe but still usable if clients +// are synchronized somehow. +// +// In this case the macro DFAKE_SCOPED_LOCK has to be +// used, it checks that if a thread is inside the push/pop then +// noone else is still inside the pop/push +// +// class NonThreadSafeQueue { +// public: +// ... +// void push(int) { DFAKE_SCOPED_LOCK(push_pop_); ... } +// int pop() { DFAKE_SCOPED_LOCK(push_pop_); ... } +// ... +// private: +// DFAKE_MUTEX(push_pop_); +// }; +// +// +// Example: Queue implementation non thread-safe but still usable if clients +// are synchronized somehow, it calls a method to "protect" from +// a "protected" method +// +// In this case the macro DFAKE_SCOPED_RECURSIVE_LOCK +// has to be used, it checks that if a thread is inside the push/pop +// then noone else is still inside the pop/push +// +// class NonThreadSafeQueue { +// public: +// void push(int) { +// DFAKE_SCOPED_LOCK(push_pop_); +// ... +// } +// int pop() { +// DFAKE_SCOPED_RECURSIVE_LOCK(push_pop_); +// bar(); +// ... +// } +// void bar() { DFAKE_SCOPED_RECURSIVE_LOCK(push_pop_); ... } +// ... +// private: +// DFAKE_MUTEX(push_pop_); +// }; +// +// +// Example: Queue implementation not usable even if clients are synchronized, +// so only one thread in the class life cycle can use the two members +// push/pop. +// +// In this case the macro DFAKE_SCOPED_LOCK_THREAD_LOCKED pins the +// specified +// critical section the first time a thread enters push or pop, from +// that time on only that thread is allowed to execute push or pop. +// +// class NonThreadSafeQueue { +// public: +// ... +// void push(int) { DFAKE_SCOPED_LOCK_THREAD_LOCKED(push_pop_); ... } +// int pop() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(push_pop_); ... } +// ... +// private: +// DFAKE_MUTEX(push_pop_); +// }; +// +// +// Example: Class that has to be contructed/destroyed on same thread, it has +// a "shareable" method (with external syncronization) and a not +// shareable method (even with external synchronization). +// +// In this case 3 Critical sections have to be defined +// +// class ExoticClass { +// public: +// ExoticClass() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(ctor_dtor_); ... } +// ~ExoticClass() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(ctor_dtor_); ... } +// +// void Shareable() { DFAKE_SCOPED_LOCK(shareable_section_); ... } +// void NotShareable() { DFAKE_SCOPED_LOCK_THREAD_LOCKED(ctor_dtor_); ... } +// ... +// private: +// DFAKE_MUTEX(ctor_dtor_); +// DFAKE_MUTEX(shareable_section_); +// }; + + +#if !defined(NDEBUG) + +// Defines a class member that acts like a mutex. It is used only as a +// verification tool. +#define DFAKE_MUTEX(obj) \ + mutable base::ThreadCollisionWarner obj +// Asserts the call is never called simultaneously in two threads. Used at +// member function scope. +#define DFAKE_SCOPED_LOCK(obj) \ + base::ThreadCollisionWarner::ScopedCheck s_check_##obj(&obj) +// Asserts the call is never called simultaneously in two threads. Used at +// member function scope. Same as DFAKE_SCOPED_LOCK but allows recursive locks. +#define DFAKE_SCOPED_RECURSIVE_LOCK(obj) \ + base::ThreadCollisionWarner::ScopedRecursiveCheck sr_check_##obj(&obj) +// Asserts the code is always executed in the same thread. +#define DFAKE_SCOPED_LOCK_THREAD_LOCKED(obj) \ + base::ThreadCollisionWarner::Check check_##obj(&obj) + +#else + +#define DFAKE_MUTEX(obj) +#define DFAKE_SCOPED_LOCK(obj) ((void)0) +#define DFAKE_SCOPED_RECURSIVE_LOCK(obj) ((void)0) +#define DFAKE_SCOPED_LOCK_THREAD_LOCKED(obj) ((void)0) + +#endif + +namespace base { + +// The class ThreadCollisionWarner uses an Asserter to notify the collision +// AsserterBase is the interfaces and DCheckAsserter is the default asserter +// used. During the unit tests is used another class that doesn't "DCHECK" +// in case of collision (check thread_collision_warner_unittests.cc) +struct BASE_EXPORT AsserterBase { + virtual ~AsserterBase() {} + virtual void warn() = 0; +}; + +struct BASE_EXPORT DCheckAsserter : public AsserterBase { + virtual ~DCheckAsserter() {} + virtual void warn(); +}; + +class BASE_EXPORT ThreadCollisionWarner { + public: + // The parameter asserter is there only for test purpose + ThreadCollisionWarner(AsserterBase* asserter = new DCheckAsserter()) + : valid_thread_id_(0), + counter_(0), + asserter_(asserter) {} + + ~ThreadCollisionWarner() { + delete asserter_; + } + + // This class is meant to be used through the macro + // DFAKE_SCOPED_LOCK_THREAD_LOCKED + // it doesn't leave the critical section, as opposed to ScopedCheck, + // because the critical section being pinned is allowed to be used only + // from one thread + class BASE_EXPORT Check { + public: + explicit Check(ThreadCollisionWarner* warner) + : warner_(warner) { + warner_->EnterSelf(); + } + + ~Check() {} + + private: + ThreadCollisionWarner* warner_; + + DISALLOW_COPY_AND_ASSIGN(Check); + }; + + // This class is meant to be used through the macro + // DFAKE_SCOPED_LOCK + class BASE_EXPORT ScopedCheck { + public: + explicit ScopedCheck(ThreadCollisionWarner* warner) + : warner_(warner) { + warner_->Enter(); + } + + ~ScopedCheck() { + warner_->Leave(); + } + + private: + ThreadCollisionWarner* warner_; + + DISALLOW_COPY_AND_ASSIGN(ScopedCheck); + }; + + // This class is meant to be used through the macro + // DFAKE_SCOPED_RECURSIVE_LOCK + class BASE_EXPORT ScopedRecursiveCheck { + public: + explicit ScopedRecursiveCheck(ThreadCollisionWarner* warner) + : warner_(warner) { + warner_->EnterSelf(); + } + + ~ScopedRecursiveCheck() { + warner_->Leave(); + } + + private: + ThreadCollisionWarner* warner_; + + DISALLOW_COPY_AND_ASSIGN(ScopedRecursiveCheck); + }; + + private: + // This method stores the current thread identifier and does a DCHECK + // if a another thread has already done it, it is safe if same thread + // calls this multiple time (recursion allowed). + void EnterSelf(); + + // Same as EnterSelf but recursion is not allowed. + void Enter(); + + // Removes the thread_id stored in order to allow other threads to + // call EnterSelf or Enter. + void Leave(); + + // This stores the thread id that is inside the critical section, if the + // value is 0 then no thread is inside. + volatile subtle::Atomic32 valid_thread_id_; + + // Counter to trace how many time a critical section was "pinned" + // (when allowed) in order to unpin it when counter_ reaches 0. + volatile subtle::Atomic32 counter_; + + // Here only for class unit tests purpose, during the test I need to not + // DCHECK but notify the collision with something else. + AsserterBase* asserter_; + + DISALLOW_COPY_AND_ASSIGN(ThreadCollisionWarner); +}; + +} // namespace base + +#endif // BASE_THREADING_THREAD_COLLISION_WARNER_H_ |