The Tor Browser: comparison ipc/chromium/src/base/thread_collision

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+:848657369898
+// Copyright (c) 2008 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_THREAD_COLLISION_WARNER_H_
+#define BASE_THREAD_COLLISION_WARNER_H_
+#include <memory.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 AsserterBase {
+virtual ~AsserterBase() {}
+virtual void warn() = 0;
+};
+struct DCheckAsserter : public AsserterBase {
+virtual ~DCheckAsserter() {}
+virtual void warn();
+};
+class 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 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 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 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_THREAD_COLLISION_WARNER_H_

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comparison: ipc/chromium/src/base/thread_collision_warner.h

ipc/chromium/src/base/thread_collision_warner.h