The Tor Browser: security/sandbox/chromium/base/threading/thread_collision

security/sandbox/chromium/base/threading/thread_collision_warner.h@925c144e1f1f (annotated)

security/sandbox/chromium/base/threading/thread_collision_warner.h

Fri, 16 Jan 2015 18:13:44 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Fri, 16 Jan 2015 18:13:44 +0100
branch: TOR_BUG_9701
changeset 14: 925c144e1f1f
permissions: -rw-r--r--

Integrate suggestion from review to improve consistency with existing code.

 // Copyright (c) 2012 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_
 #include <memory>
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/compiler_specific.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 synchronization) 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) typedef void InternalFakeMutexType##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() OVERRIDE;
 };
 class BASE_EXPORT ThreadCollisionWarner {
  public:
   // The parameter asserter is there only for test purpose
   explicit 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_

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security/sandbox/chromium/base/threading/thread_collision_warner.h@925c144e1f1f (annotated)

security/sandbox/chromium/base/threading/thread_collision_warner.h