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+// 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_