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

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

security/sandbox/chromium/base/threading/thread_restrictions.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_RESTRICTIONS_H_
 #define BASE_THREADING_THREAD_RESTRICTIONS_H_
 #include "base/base_export.h"
 #include "base/basictypes.h"
 // See comment at top of thread_checker.h
 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
 #define ENABLE_THREAD_RESTRICTIONS 1
 #else
 #define ENABLE_THREAD_RESTRICTIONS 0
 #endif
 class AcceleratedPresenter;
 class BrowserProcessImpl;
 class HistogramSynchronizer;
 class MetricsService;
 class NativeBackendKWallet;
 class ScopedAllowWaitForLegacyWebViewApi;
 class TestingAutomationProvider;
 namespace browser_sync {
 class NonFrontendDataTypeController;
 class UIModelWorker;
 }
 namespace cc {
 class CompletionEvent;
 }
 namespace chromeos {
 class AudioMixerAlsa;
 class BlockingMethodCaller;
 namespace system {
 class StatisticsProviderImpl;
 }
 }
 namespace chrome_browser_net {
 class Predictor;
 }
 namespace content {
 class BrowserGpuChannelHostFactory;
 class BrowserShutdownProfileDumper;
 class BrowserTestBase;
 class GLHelper;
 class GpuChannelHost;
 class NestedMessagePumpAndroid;
 class RenderWidgetHelper;
 class ScopedAllowWaitForAndroidLayoutTests;
 class TextInputClientMac;
 }
 namespace dbus {
 class Bus;
 }
 namespace disk_cache {
 class BackendImpl;
 class InFlightIO;
 }
 namespace media {
 class AudioOutputController;
 }
 namespace net {
 class FileStreamPosix;
 class FileStreamWin;
 namespace internal {
 class AddressTrackerLinux;
 }
 }
 namespace remoting {
 class AutoThread;
 }
 namespace base {
 namespace android {
 class JavaHandlerThread;
 }
 class SequencedWorkerPool;
 class SimpleThread;
 class Thread;
 class ThreadTestHelper;
 // Certain behavior is disallowed on certain threads.  ThreadRestrictions helps
 // enforce these rules.  Examples of such rules:
 //
 // * Do not do blocking IO (makes the thread janky)
 // * Do not access Singleton/LazyInstance (may lead to shutdown crashes)
 //
 // Here's more about how the protection works:
 //
 // 1) If a thread should not be allowed to make IO calls, mark it:
 //      base::ThreadRestrictions::SetIOAllowed(false);
 //    By default, threads *are* allowed to make IO calls.
 //    In Chrome browser code, IO calls should be proxied to the File thread.
 //
 // 2) If a function makes a call that will go out to disk, check whether the
 //    current thread is allowed:
 //      base::ThreadRestrictions::AssertIOAllowed();
 //
 //
 // Style tip: where should you put AssertIOAllowed checks?  It's best
 // if you put them as close to the disk access as possible, at the
 // lowest level.  This rule is simple to follow and helps catch all
 // callers.  For example, if your function GoDoSomeBlockingDiskCall()
 // only calls other functions in Chrome and not fopen(), you should go
 // add the AssertIOAllowed checks in the helper functions.
 class BASE_EXPORT ThreadRestrictions {
  public:
   // Constructing a ScopedAllowIO temporarily allows IO for the current
   // thread.  Doing this is almost certainly always incorrect.
   class BASE_EXPORT ScopedAllowIO {
    public:
     ScopedAllowIO() { previous_value_ = SetIOAllowed(true); }
     ~ScopedAllowIO() { SetIOAllowed(previous_value_); }
    private:
     // Whether IO is allowed when the ScopedAllowIO was constructed.
     bool previous_value_;
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO);
   };
   // Constructing a ScopedAllowSingleton temporarily allows accessing for the
   // current thread.  Doing this is almost always incorrect.
   class BASE_EXPORT ScopedAllowSingleton {
    public:
     ScopedAllowSingleton() { previous_value_ = SetSingletonAllowed(true); }
     ~ScopedAllowSingleton() { SetSingletonAllowed(previous_value_); }
    private:
     // Whether singleton use is allowed when the ScopedAllowSingleton was
     // constructed.
     bool previous_value_;
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowSingleton);
   };
 #if ENABLE_THREAD_RESTRICTIONS
   // Set whether the current thread to make IO calls.
   // Threads start out in the *allowed* state.
   // Returns the previous value.
   static bool SetIOAllowed(bool allowed);
   // Check whether the current thread is allowed to make IO calls,
   // and DCHECK if not.  See the block comment above the class for
   // a discussion of where to add these checks.
   static void AssertIOAllowed();
   // Set whether the current thread can use singletons.  Returns the previous
   // value.
   static bool SetSingletonAllowed(bool allowed);
   // Check whether the current thread is allowed to use singletons (Singleton /
   // LazyInstance).  DCHECKs if not.
   static void AssertSingletonAllowed();
   // Disable waiting on the current thread. Threads start out in the *allowed*
   // state. Returns the previous value.
   static void DisallowWaiting();
   // Check whether the current thread is allowed to wait, and DCHECK if not.
   static void AssertWaitAllowed();
 #else
   // Inline the empty definitions of these functions so that they can be
   // compiled out.
   static bool SetIOAllowed(bool allowed) { return true; }
   static void AssertIOAllowed() {}
   static bool SetSingletonAllowed(bool allowed) { return true; }
   static void AssertSingletonAllowed() {}
   static void DisallowWaiting() {}
   static void AssertWaitAllowed() {}
 #endif
  private:
   // DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to jam or brettw first.
   // BEGIN ALLOWED USAGE.
   friend class content::BrowserShutdownProfileDumper;
   friend class content::BrowserTestBase;
   friend class content::NestedMessagePumpAndroid;
   friend class content::RenderWidgetHelper;
   friend class content::ScopedAllowWaitForAndroidLayoutTests;
   friend class ::HistogramSynchronizer;
   friend class ::ScopedAllowWaitForLegacyWebViewApi;
   friend class ::TestingAutomationProvider;
   friend class cc::CompletionEvent;
   friend class remoting::AutoThread;
   friend class MessagePumpDefault;
   friend class SequencedWorkerPool;
   friend class SimpleThread;
   friend class Thread;
   friend class ThreadTestHelper;
   friend class PlatformThread;
   friend class android::JavaHandlerThread;
   // END ALLOWED USAGE.
   // BEGIN USAGE THAT NEEDS TO BE FIXED.
   friend class ::chromeos::AudioMixerAlsa;        // http://crbug.com/125206
   friend class ::chromeos::BlockingMethodCaller;  // http://crbug.com/125360
   friend class ::chromeos::system::StatisticsProviderImpl;  // http://crbug.com/125385
   friend class browser_sync::NonFrontendDataTypeController;  // http://crbug.com/19757
   friend class browser_sync::UIModelWorker;       // http://crbug.com/19757
   friend class chrome_browser_net::Predictor;     // http://crbug.com/78451
   friend class
       content::BrowserGpuChannelHostFactory;      // http://crbug.com/125248
   friend class content::GLHelper;                 // http://crbug.com/125415
   friend class content::GpuChannelHost;           // http://crbug.com/125264
   friend class content::TextInputClientMac;       // http://crbug.com/121917
   friend class dbus::Bus;                         // http://crbug.com/125222
   friend class disk_cache::BackendImpl;           // http://crbug.com/74623
   friend class disk_cache::InFlightIO;            // http://crbug.com/74623
   friend class media::AudioOutputController;      // http://crbug.com/120973
   friend class net::FileStreamPosix;              // http://crbug.com/115067
   friend class net::FileStreamWin;                // http://crbug.com/115067
   friend class net::internal::AddressTrackerLinux;  // http://crbug.com/125097
   friend class ::AcceleratedPresenter;            // http://crbug.com/125391
   friend class ::BrowserProcessImpl;              // http://crbug.com/125207
   friend class ::MetricsService;                  // http://crbug.com/124954
   friend class ::NativeBackendKWallet;            // http://crbug.com/125331
   // END USAGE THAT NEEDS TO BE FIXED.
 #if ENABLE_THREAD_RESTRICTIONS
   static bool SetWaitAllowed(bool allowed);
 #else
   static bool SetWaitAllowed(bool allowed) { return true; }
 #endif
   // Constructing a ScopedAllowWait temporarily allows waiting on the current
   // thread.  Doing this is almost always incorrect, which is why we limit who
   // can use this through friend. If you find yourself needing to use this, find
   // another way. Talk to jam or brettw.
   class BASE_EXPORT ScopedAllowWait {
    public:
     ScopedAllowWait() { previous_value_ = SetWaitAllowed(true); }
     ~ScopedAllowWait() { SetWaitAllowed(previous_value_); }
    private:
     // Whether singleton use is allowed when the ScopedAllowWait was
     // constructed.
     bool previous_value_;
     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
   };
   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 };
 }  // namespace base
 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_

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

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