base/threading/thread_restrictions.h - cobalt - Git at Google

 // 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/gtest_prod_util.h"
 #include "base/logging.h"
 #include "base/macros.h"

 class BrowserProcessImpl;
 class HistogramSynchronizer;
 class NativeBackendKWallet;
 class KeyStorageLinux;

 namespace android_webview {
 class AwFormDatabaseService;
 class CookieManager;
 class ScopedAllowInitGLBindings;
 }
 namespace audio {
 class OutputDevice;
 }
 namespace blink {
 class VideoFrameResourceProvider;
 }
 namespace cc {
 class CompletionEvent;
 class SingleThreadTaskGraphRunner;
 }
 namespace chromeos {
 class BlockingMethodCaller;
 namespace system {
 class StatisticsProviderImpl;
 }
 }
 namespace chrome_browser_net {
 class Predictor;
 }
 namespace content {
 class BrowserGpuChannelHostFactory;
 class BrowserMainLoop;
 class BrowserProcessSubThread;
 class BrowserShutdownProfileDumper;
 class BrowserTestBase;
 class CategorizedWorkerPool;
 class GpuProcessTransportFactory;
 class NestedMessagePumpAndroid;
 class ScopedAllowWaitForAndroidLayoutTests;
 class ScopedAllowWaitForDebugURL;
 class SessionStorageDatabase;
 class SoftwareOutputDeviceMus;
 class ServiceWorkerSubresourceLoader;
 class SynchronousCompositor;
 class SynchronousCompositorHost;
 class SynchronousCompositorSyncCallBridge;
 class TextInputClientMac;
 }  // namespace content
 namespace cronet {
 class CronetPrefsManager;
 class CronetURLRequestContext;
 }  // namespace cronet
 namespace dbus {
 class Bus;
 }
 namespace disk_cache {
 class BackendImpl;
 class InFlightIO;
 }
 namespace functions {
 class ExecScriptScopedAllowBaseSyncPrimitives;
 }
 namespace gpu {
 class GpuChannelHost;
 }
 namespace leveldb {
 class LevelDBMojoProxy;
 }
 namespace media {
 class AudioInputDevice;
 class BlockingUrlProtocol;
 }
 namespace midi {
 class TaskService;  // https://crbug.com/796830
 }
 namespace mojo {
 class CoreLibraryInitializer;
 class SyncCallRestrictions;
 namespace core {
 class ScopedIPCSupport;
 }
 }
 namespace rlz_lib {
 class FinancialPing;
 }
 namespace ui {
 class CommandBufferClientImpl;
 class CommandBufferLocal;
 class GpuState;
 class MaterialDesignController;
 }
 namespace net {
 class MultiThreadedCertVerifierScopedAllowBaseSyncPrimitives;
 class NetworkChangeNotifierMac;
 namespace internal {
 class AddressTrackerLinux;
 }
 }

 namespace remoting {
 class AutoThread;
 }

 namespace resource_coordinator {
 class TabManagerDelegate;
 }

 namespace service_manager {
 class ServiceProcessLauncher;
 }

 namespace shell_integration_linux {
 class LaunchXdgUtilityScopedAllowBaseSyncPrimitives;
 }

 namespace ui {
 class WindowResizeHelperMac;
 }

 namespace viz {
 class HostGpuMemoryBufferManager;
 }

 namespace webrtc {
 class DesktopConfigurationMonitor;
 }

 namespace base {

 namespace android {
 class JavaHandlerThread;
 }

 namespace internal {
 class TaskTracker;
 }

 class AdjustOOMScoreHelper;
 class GetAppOutputScopedAllowBaseSyncPrimitives;
 class SimpleThread;
 class StackSamplingProfiler;
 class Thread;
 class ThreadTestHelper;

 #if DCHECK_IS_ON()
 #define INLINE_IF_DCHECK_IS_OFF BASE_EXPORT
 #define EMPTY_BODY_IF_DCHECK_IS_OFF
 #else
 #define INLINE_IF_DCHECK_IS_OFF inline
 #define EMPTY_BODY_IF_DCHECK_IS_OFF \
   {}
 #endif

 // A "blocking call" refers to any call that causes the calling thread to wait
 // off-CPU. It includes but is not limited to calls that wait on synchronous
 // file I/O operations: read or write a file from disk, interact with a pipe or
 // a socket, rename or delete a file, enumerate files in a directory, etc.
 // Acquiring a low contention lock is not considered a blocking call.

 // Asserts that blocking calls are allowed in the current scope. Prefer using
 // ScopedBlockingCall instead, which also serves as a precise annotation of the
 // scope that may/will block.
 //
 // Style tip: It's best if you put AssertBlockingAllowed() checks as close to
 // the blocking call as possible. For example:
 //
 // void ReadFile() {
 //   PreWork();
 //
 //   base::AssertBlockingAllowed();
 //   fopen(...);
 //
 //   PostWork();
 // }
 //
 // void Bar() {
 //   ReadFile();
 // }
 //
 // void Foo() {
 //   Bar();
 // }
 INLINE_IF_DCHECK_IS_OFF void AssertBlockingAllowed()
     EMPTY_BODY_IF_DCHECK_IS_OFF;

 // Disallows blocking on the current thread.
 INLINE_IF_DCHECK_IS_OFF void DisallowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;

 // Disallows blocking calls within its scope.
 class BASE_EXPORT ScopedDisallowBlocking {
  public:
   ScopedDisallowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;
   ~ScopedDisallowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;

  private:
 #if DCHECK_IS_ON()
   const bool was_disallowed_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(ScopedDisallowBlocking);
 };

 // ScopedAllowBlocking(ForTesting) allow blocking calls within a scope where
 // they are normally disallowed.
 //
 // Avoid using this. Prefer making blocking calls from tasks posted to
 // base::TaskScheduler with base::MayBlock().
 //
 // Where unavoidable, put ScopedAllow* instances in the narrowest scope possible
 // in the caller making the blocking call but no further down. That is: if a
 // Cleanup() method needs to do a blocking call, document Cleanup() as blocking
 // and add a ScopedAllowBlocking instance in callers that can't avoid making
 // this call from a context where blocking is banned, as such:
 //   void Client::MyMethod() {
 //     (...)
 //     {
 //       // Blocking is okay here because XYZ.
 //       ScopedAllowBlocking allow_blocking;
 //       my_foo_->Cleanup();
 //     }
 //     (...)
 //   }
 //
 //   // This method can block.
 //   void Foo::Cleanup() {
 //     // Do NOT add the ScopedAllowBlocking in Cleanup() directly as that hides
 //     // its blocking nature from unknowing callers and defeats the purpose of
 //     // these checks.
 //     FlushStateToDisk();
 //   }
 //
 // Note: In rare situations where the blocking call is an implementation detail
 // (i.e. the impl makes a call that invokes AssertBlockingAllowed() but it
 // somehow knows that in practice this will not block), it might be okay to hide
 // the ScopedAllowBlocking instance in the impl with a comment explaining why
 // that's okay.
 class BASE_EXPORT ScopedAllowBlocking {
  private:
   // This can only be instantiated by friends. Use ScopedAllowBlockingForTesting
   // in unit tests to avoid the friend requirement.
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest, ScopedAllowBlocking);
   friend class AdjustOOMScoreHelper;
   friend class android_webview::ScopedAllowInitGLBindings;
   friend class audio::OutputDevice;
   friend class content::BrowserProcessSubThread;
   friend class content::GpuProcessTransportFactory;
   friend class cronet::CronetPrefsManager;
   friend class cronet::CronetURLRequestContext;
   friend class media::AudioInputDevice;
   friend class mojo::CoreLibraryInitializer;
   friend class resource_coordinator::TabManagerDelegate;  // crbug.com/778703
   friend class ui::MaterialDesignController;
   friend class ScopedAllowBlockingForTesting;
   friend class StackSamplingProfiler;

   ScopedAllowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;
   ~ScopedAllowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;

 #if DCHECK_IS_ON()
   const bool was_disallowed_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(ScopedAllowBlocking);
 };

 class ScopedAllowBlockingForTesting {
  public:
   ScopedAllowBlockingForTesting() {}
   ~ScopedAllowBlockingForTesting() {}

  private:
 #if DCHECK_IS_ON()
   ScopedAllowBlocking scoped_allow_blocking_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(ScopedAllowBlockingForTesting);
 };

 // "Waiting on a //base sync primitive" refers to calling one of these methods:
 // - base::WaitableEvent::*Wait*
 // - base::ConditionVariable::*Wait*
 // - base::Process::WaitForExit*

 // Disallows waiting on a //base sync primitive on the current thread.
 INLINE_IF_DCHECK_IS_OFF void DisallowBaseSyncPrimitives()
     EMPTY_BODY_IF_DCHECK_IS_OFF;

 // ScopedAllowBaseSyncPrimitives(ForTesting)(OutsideBlockingScope) allow waiting
 // on a //base sync primitive within a scope where this is normally disallowed.
 //
 // Avoid using this.
 //
 // Instead of waiting on a WaitableEvent or a ConditionVariable, put the work
 // that should happen after the wait in a callback and post that callback from
 // where the WaitableEvent or ConditionVariable would have been signaled. If
 // something needs to be scheduled after many tasks have executed, use
 // base::BarrierClosure.
 //
 // On Windows, join processes asynchronously using base::win::ObjectWatcher.

 // This can only be used in a scope where blocking is allowed.
 class BASE_EXPORT ScopedAllowBaseSyncPrimitives {
  private:
   // This can only be instantiated by friends. Use
   // ScopedAllowBaseSyncPrimitivesForTesting in unit tests to avoid the friend
   // requirement.
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
                            ScopedAllowBaseSyncPrimitives);
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
                            ScopedAllowBaseSyncPrimitivesResetsState);
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
                            ScopedAllowBaseSyncPrimitivesWithBlockingDisallowed);
   friend class base::GetAppOutputScopedAllowBaseSyncPrimitives;
   friend class content::BrowserProcessSubThread;
   friend class content::SessionStorageDatabase;
   friend class functions::ExecScriptScopedAllowBaseSyncPrimitives;
   friend class leveldb::LevelDBMojoProxy;
   friend class media::BlockingUrlProtocol;
   friend class mojo::core::ScopedIPCSupport;
   friend class net::MultiThreadedCertVerifierScopedAllowBaseSyncPrimitives;
   friend class rlz_lib::FinancialPing;
   friend class shell_integration_linux::
       LaunchXdgUtilityScopedAllowBaseSyncPrimitives;
   friend class webrtc::DesktopConfigurationMonitor;
   friend class content::ServiceWorkerSubresourceLoader;
   friend class blink::VideoFrameResourceProvider;

   ScopedAllowBaseSyncPrimitives() EMPTY_BODY_IF_DCHECK_IS_OFF;
   ~ScopedAllowBaseSyncPrimitives() EMPTY_BODY_IF_DCHECK_IS_OFF;

 #if DCHECK_IS_ON()
   const bool was_disallowed_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(ScopedAllowBaseSyncPrimitives);
 };

 // This can be used in a scope where blocking is disallowed.
 class BASE_EXPORT ScopedAllowBaseSyncPrimitivesOutsideBlockingScope {
  private:
   // This can only be instantiated by friends. Use
   // ScopedAllowBaseSyncPrimitivesForTesting in unit tests to avoid the friend
   // requirement.
   FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
                            ScopedAllowBaseSyncPrimitivesOutsideBlockingScope);
   FRIEND_TEST_ALL_PREFIXES(
       ThreadRestrictionsTest,
       ScopedAllowBaseSyncPrimitivesOutsideBlockingScopeResetsState);
   friend class ::KeyStorageLinux;
   friend class content::SynchronousCompositor;
   friend class content::SynchronousCompositorHost;
   friend class content::SynchronousCompositorSyncCallBridge;
   friend class midi::TaskService;  // https://crbug.com/796830
   // Not used in production yet, https://crbug.com/844078.
   friend class service_manager::ServiceProcessLauncher;
   friend class viz::HostGpuMemoryBufferManager;

   ScopedAllowBaseSyncPrimitivesOutsideBlockingScope()
       EMPTY_BODY_IF_DCHECK_IS_OFF;
   ~ScopedAllowBaseSyncPrimitivesOutsideBlockingScope()
       EMPTY_BODY_IF_DCHECK_IS_OFF;

 #if DCHECK_IS_ON()
   const bool was_disallowed_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(ScopedAllowBaseSyncPrimitivesOutsideBlockingScope);
 };

 // This can be used in tests without being a friend of
 // ScopedAllowBaseSyncPrimitives(OutsideBlockingScope).
 class BASE_EXPORT ScopedAllowBaseSyncPrimitivesForTesting {
  public:
   ScopedAllowBaseSyncPrimitivesForTesting() EMPTY_BODY_IF_DCHECK_IS_OFF;
   ~ScopedAllowBaseSyncPrimitivesForTesting() EMPTY_BODY_IF_DCHECK_IS_OFF;

  private:
 #if DCHECK_IS_ON()
   const bool was_disallowed_;
 #endif

   DISALLOW_COPY_AND_ASSIGN(ScopedAllowBaseSyncPrimitivesForTesting);
 };

 namespace internal {

 // Asserts that waiting on a //base sync primitive is allowed in the current
 // scope.
 INLINE_IF_DCHECK_IS_OFF void AssertBaseSyncPrimitivesAllowed()
     EMPTY_BODY_IF_DCHECK_IS_OFF;

 // Resets all thread restrictions on the current thread.
 INLINE_IF_DCHECK_IS_OFF void ResetThreadRestrictionsForTesting()
     EMPTY_BODY_IF_DCHECK_IS_OFF;

 }  // namespace internal

 // "Long CPU" work refers to any code that takes more than 100 ms to
 // run when there is no CPU contention and no hard page faults and therefore,
 // is not suitable to run on a thread required to keep the browser responsive
 // (where jank could be visible to the user).

 // Asserts that running long CPU work is allowed in the current scope.
 INLINE_IF_DCHECK_IS_OFF void AssertLongCPUWorkAllowed()
     EMPTY_BODY_IF_DCHECK_IS_OFF;

 // Disallows all tasks that may be unresponsive on the current thread. This
 // disallows blocking calls, waiting on a //base sync primitive and long CPU
 // work.
 INLINE_IF_DCHECK_IS_OFF void DisallowUnresponsiveTasks()
     EMPTY_BODY_IF_DCHECK_IS_OFF;

 class BASE_EXPORT ThreadRestrictions {
  public:
   // Constructing a ScopedAllowIO temporarily allows IO for the current
   // thread.  Doing this is almost certainly always incorrect.
   //
   // DEPRECATED. Use ScopedAllowBlocking(ForTesting).
   class BASE_EXPORT ScopedAllowIO {
    public:
     ScopedAllowIO() EMPTY_BODY_IF_DCHECK_IS_OFF;
     ~ScopedAllowIO() EMPTY_BODY_IF_DCHECK_IS_OFF;

    private:
 #if DCHECK_IS_ON()
     const bool was_allowed_;
 #endif

     DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO);
   };

 #if DCHECK_IS_ON()
   // Set whether the current thread to make IO calls.
   // Threads start out in the *allowed* state.
   // Returns the previous value.
   //
   // DEPRECATED. Use ScopedAllowBlocking(ForTesting) or ScopedDisallowBlocking.
   static bool SetIOAllowed(bool allowed);

   // 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.
   //
   // DEPRECATED. Use DisallowBaseSyncPrimitives.
   static void DisallowWaiting();
 #if defined(STARBOARD)
   // Get whether the current thread can use singletons.
   static bool GetSingletonAllowed();
 #endif  // defined(STARBOARD)
 #else
   // Inline the empty definitions of these functions so that they can be
   // compiled out.
   static bool SetIOAllowed(bool allowed) { return true; }
   static bool SetSingletonAllowed(bool allowed) { return true; }
   static void AssertSingletonAllowed() {}
   static void DisallowWaiting() {}
 #if defined(STARBOARD)
   // Get whether the current thread can use singletons.
   static bool GetSingletonAllowed() {return true;}
 #endif  // defined(STARBOARD)
 #endif

  private:
   // DO NOT ADD ANY OTHER FRIEND STATEMENTS.
   // BEGIN ALLOWED USAGE.
   friend class android_webview::AwFormDatabaseService;
   friend class android_webview::CookieManager;
   friend class base::StackSamplingProfiler;
   friend class content::BrowserMainLoop;
   friend class content::BrowserShutdownProfileDumper;
   friend class content::BrowserTestBase;
   friend class content::NestedMessagePumpAndroid;
   friend class content::ScopedAllowWaitForAndroidLayoutTests;
   friend class content::ScopedAllowWaitForDebugURL;
   friend class ::HistogramSynchronizer;
   friend class internal::TaskTracker;
   friend class cc::CompletionEvent;
   friend class cc::SingleThreadTaskGraphRunner;
   friend class content::CategorizedWorkerPool;
   friend class remoting::AutoThread;
   friend class ui::WindowResizeHelperMac;
   friend class MessagePumpDefault;
   friend class SimpleThread;
   friend class Thread;
   friend class ThreadTestHelper;
   friend class PlatformThread;
   friend class android::JavaHandlerThread;
   friend class mojo::SyncCallRestrictions;
   friend class ui::CommandBufferClientImpl;
   friend class ui::CommandBufferLocal;
   friend class ui::GpuState;

   // END ALLOWED USAGE.
   // BEGIN USAGE THAT NEEDS TO BE FIXED.
   friend class ::chromeos::BlockingMethodCaller;  // http://crbug.com/125360
   friend class ::chromeos::system::StatisticsProviderImpl;  // http://crbug.com/125385
   friend class chrome_browser_net::Predictor;     // http://crbug.com/78451
   friend class
       content::BrowserGpuChannelHostFactory;      // http://crbug.com/125248
   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 gpu::GpuChannelHost;               // http://crbug.com/125264
   friend class net::internal::AddressTrackerLinux;  // http://crbug.com/125097
   friend class net::NetworkChangeNotifierMac;     // http://crbug.com/125097
   friend class ::BrowserProcessImpl;              // http://crbug.com/125207
   friend class ::NativeBackendKWallet;            // http://crbug.com/125331
 #if !defined(OFFICIAL_BUILD)
   friend class content::SoftwareOutputDeviceMus;  // Interim non-production code
 #endif
 // END USAGE THAT NEEDS TO BE FIXED.

 #if DCHECK_IS_ON()
   // DEPRECATED. Use ScopedAllowBaseSyncPrimitives.
   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.
   //
   // DEPRECATED. Use ScopedAllowBaseSyncPrimitives.
   class BASE_EXPORT ScopedAllowWait {
    public:
     ScopedAllowWait() EMPTY_BODY_IF_DCHECK_IS_OFF;
     ~ScopedAllowWait() EMPTY_BODY_IF_DCHECK_IS_OFF;

    private:
 #if DCHECK_IS_ON()
     const bool was_allowed_;
 #endif

     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
   };

   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 };

 }  // namespace base

 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_
	// 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/gtest_prod_util.h"
	#include "base/logging.h"
	#include "base/macros.h"

	class BrowserProcessImpl;
	class HistogramSynchronizer;
	class NativeBackendKWallet;
	class KeyStorageLinux;

	namespace android_webview {
	class AwFormDatabaseService;
	class CookieManager;
	class ScopedAllowInitGLBindings;
	}
	namespace audio {
	class OutputDevice;
	}
	namespace blink {
	class VideoFrameResourceProvider;
	}
	namespace cc {
	class CompletionEvent;
	class SingleThreadTaskGraphRunner;
	}
	namespace chromeos {
	class BlockingMethodCaller;
	namespace system {
	class StatisticsProviderImpl;
	}
	}
	namespace chrome_browser_net {
	class Predictor;
	}
	namespace content {
	class BrowserGpuChannelHostFactory;
	class BrowserMainLoop;
	class BrowserProcessSubThread;
	class BrowserShutdownProfileDumper;
	class BrowserTestBase;
	class CategorizedWorkerPool;
	class GpuProcessTransportFactory;
	class NestedMessagePumpAndroid;
	class ScopedAllowWaitForAndroidLayoutTests;
	class ScopedAllowWaitForDebugURL;
	class SessionStorageDatabase;
	class SoftwareOutputDeviceMus;
	class ServiceWorkerSubresourceLoader;
	class SynchronousCompositor;
	class SynchronousCompositorHost;
	class SynchronousCompositorSyncCallBridge;
	class TextInputClientMac;
	} // namespace content
	namespace cronet {
	class CronetPrefsManager;
	class CronetURLRequestContext;
	} // namespace cronet
	namespace dbus {
	class Bus;
	}
	namespace disk_cache {
	class BackendImpl;
	class InFlightIO;
	}
	namespace functions {
	class ExecScriptScopedAllowBaseSyncPrimitives;
	}
	namespace gpu {
	class GpuChannelHost;
	}
	namespace leveldb {
	class LevelDBMojoProxy;
	}
	namespace media {
	class AudioInputDevice;
	class BlockingUrlProtocol;
	}
	namespace midi {
	class TaskService; // https://crbug.com/796830
	}
	namespace mojo {
	class CoreLibraryInitializer;
	class SyncCallRestrictions;
	namespace core {
	class ScopedIPCSupport;
	}
	}
	namespace rlz_lib {
	class FinancialPing;
	}
	namespace ui {
	class CommandBufferClientImpl;
	class CommandBufferLocal;
	class GpuState;
	class MaterialDesignController;
	}
	namespace net {
	class MultiThreadedCertVerifierScopedAllowBaseSyncPrimitives;
	class NetworkChangeNotifierMac;
	namespace internal {
	class AddressTrackerLinux;
	}
	}

	namespace remoting {
	class AutoThread;
	}

	namespace resource_coordinator {
	class TabManagerDelegate;
	}

	namespace service_manager {
	class ServiceProcessLauncher;
	}

	namespace shell_integration_linux {
	class LaunchXdgUtilityScopedAllowBaseSyncPrimitives;
	}

	namespace ui {
	class WindowResizeHelperMac;
	}

	namespace viz {
	class HostGpuMemoryBufferManager;
	}

	namespace webrtc {
	class DesktopConfigurationMonitor;
	}

	namespace base {

	namespace android {
	class JavaHandlerThread;
	}

	namespace internal {
	class TaskTracker;
	}

	class AdjustOOMScoreHelper;
	class GetAppOutputScopedAllowBaseSyncPrimitives;
	class SimpleThread;
	class StackSamplingProfiler;
	class Thread;
	class ThreadTestHelper;

	#if DCHECK_IS_ON()
	#define INLINE_IF_DCHECK_IS_OFF BASE_EXPORT
	#define EMPTY_BODY_IF_DCHECK_IS_OFF
	#else
	#define INLINE_IF_DCHECK_IS_OFF inline
	#define EMPTY_BODY_IF_DCHECK_IS_OFF \
	{}
	#endif

	// A "blocking call" refers to any call that causes the calling thread to wait
	// off-CPU. It includes but is not limited to calls that wait on synchronous
	// file I/O operations: read or write a file from disk, interact with a pipe or
	// a socket, rename or delete a file, enumerate files in a directory, etc.
	// Acquiring a low contention lock is not considered a blocking call.

	// Asserts that blocking calls are allowed in the current scope. Prefer using
	// ScopedBlockingCall instead, which also serves as a precise annotation of the
	// scope that may/will block.
	//
	// Style tip: It's best if you put AssertBlockingAllowed() checks as close to
	// the blocking call as possible. For example:
	//
	// void ReadFile() {
	// PreWork();
	//
	// base::AssertBlockingAllowed();
	// fopen(...);
	//
	// PostWork();
	// }
	//
	// void Bar() {
	// ReadFile();
	// }
	//
	// void Foo() {
	// Bar();
	// }
	INLINE_IF_DCHECK_IS_OFF void AssertBlockingAllowed()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	// Disallows blocking on the current thread.
	INLINE_IF_DCHECK_IS_OFF void DisallowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;

	// Disallows blocking calls within its scope.
	class BASE_EXPORT ScopedDisallowBlocking {
	public:
	ScopedDisallowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedDisallowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;

	private:
	#if DCHECK_IS_ON()
	const bool was_disallowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedDisallowBlocking);
	};

	// ScopedAllowBlocking(ForTesting) allow blocking calls within a scope where
	// they are normally disallowed.
	//
	// Avoid using this. Prefer making blocking calls from tasks posted to
	// base::TaskScheduler with base::MayBlock().
	//
	// Where unavoidable, put ScopedAllow* instances in the narrowest scope possible
	// in the caller making the blocking call but no further down. That is: if a
	// Cleanup() method needs to do a blocking call, document Cleanup() as blocking
	// and add a ScopedAllowBlocking instance in callers that can't avoid making
	// this call from a context where blocking is banned, as such:
	// void Client::MyMethod() {
	// (...)
	// {
	// // Blocking is okay here because XYZ.
	// ScopedAllowBlocking allow_blocking;
	// my_foo_->Cleanup();
	// }
	// (...)
	// }
	//
	// // This method can block.
	// void Foo::Cleanup() {
	// // Do NOT add the ScopedAllowBlocking in Cleanup() directly as that hides
	// // its blocking nature from unknowing callers and defeats the purpose of
	// // these checks.
	// FlushStateToDisk();
	// }
	//
	// Note: In rare situations where the blocking call is an implementation detail
	// (i.e. the impl makes a call that invokes AssertBlockingAllowed() but it
	// somehow knows that in practice this will not block), it might be okay to hide
	// the ScopedAllowBlocking instance in the impl with a comment explaining why
	// that's okay.
	class BASE_EXPORT ScopedAllowBlocking {
	private:
	// This can only be instantiated by friends. Use ScopedAllowBlockingForTesting
	// in unit tests to avoid the friend requirement.
	FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest, ScopedAllowBlocking);
	friend class AdjustOOMScoreHelper;
	friend class android_webview::ScopedAllowInitGLBindings;
	friend class audio::OutputDevice;
	friend class content::BrowserProcessSubThread;
	friend class content::GpuProcessTransportFactory;
	friend class cronet::CronetPrefsManager;
	friend class cronet::CronetURLRequestContext;
	friend class media::AudioInputDevice;
	friend class mojo::CoreLibraryInitializer;
	friend class resource_coordinator::TabManagerDelegate; // crbug.com/778703
	friend class ui::MaterialDesignController;
	friend class ScopedAllowBlockingForTesting;
	friend class StackSamplingProfiler;

	ScopedAllowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedAllowBlocking() EMPTY_BODY_IF_DCHECK_IS_OFF;

	#if DCHECK_IS_ON()
	const bool was_disallowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowBlocking);
	};

	class ScopedAllowBlockingForTesting {
	public:
	ScopedAllowBlockingForTesting() {}
	~ScopedAllowBlockingForTesting() {}

	private:
	#if DCHECK_IS_ON()
	ScopedAllowBlocking scoped_allow_blocking_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowBlockingForTesting);
	};

	// "Waiting on a //base sync primitive" refers to calling one of these methods:
	// - base::WaitableEvent::Wait
	// - base::ConditionVariable::Wait
	// - base::Process::WaitForExit*

	// Disallows waiting on a //base sync primitive on the current thread.
	INLINE_IF_DCHECK_IS_OFF void DisallowBaseSyncPrimitives()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	// ScopedAllowBaseSyncPrimitives(ForTesting)(OutsideBlockingScope) allow waiting
	// on a //base sync primitive within a scope where this is normally disallowed.
	//
	// Avoid using this.
	//
	// Instead of waiting on a WaitableEvent or a ConditionVariable, put the work
	// that should happen after the wait in a callback and post that callback from
	// where the WaitableEvent or ConditionVariable would have been signaled. If
	// something needs to be scheduled after many tasks have executed, use
	// base::BarrierClosure.
	//
	// On Windows, join processes asynchronously using base::win::ObjectWatcher.

	// This can only be used in a scope where blocking is allowed.
	class BASE_EXPORT ScopedAllowBaseSyncPrimitives {
	private:
	// This can only be instantiated by friends. Use
	// ScopedAllowBaseSyncPrimitivesForTesting in unit tests to avoid the friend
	// requirement.
	FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
	ScopedAllowBaseSyncPrimitives);
	FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
	ScopedAllowBaseSyncPrimitivesResetsState);
	FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
	ScopedAllowBaseSyncPrimitivesWithBlockingDisallowed);
	friend class base::GetAppOutputScopedAllowBaseSyncPrimitives;
	friend class content::BrowserProcessSubThread;
	friend class content::SessionStorageDatabase;
	friend class functions::ExecScriptScopedAllowBaseSyncPrimitives;
	friend class leveldb::LevelDBMojoProxy;
	friend class media::BlockingUrlProtocol;
	friend class mojo::core::ScopedIPCSupport;
	friend class net::MultiThreadedCertVerifierScopedAllowBaseSyncPrimitives;
	friend class rlz_lib::FinancialPing;
	friend class shell_integration_linux::
	LaunchXdgUtilityScopedAllowBaseSyncPrimitives;
	friend class webrtc::DesktopConfigurationMonitor;
	friend class content::ServiceWorkerSubresourceLoader;
	friend class blink::VideoFrameResourceProvider;

	ScopedAllowBaseSyncPrimitives() EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedAllowBaseSyncPrimitives() EMPTY_BODY_IF_DCHECK_IS_OFF;

	#if DCHECK_IS_ON()
	const bool was_disallowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowBaseSyncPrimitives);
	};

	// This can be used in a scope where blocking is disallowed.
	class BASE_EXPORT ScopedAllowBaseSyncPrimitivesOutsideBlockingScope {
	private:
	// This can only be instantiated by friends. Use
	// ScopedAllowBaseSyncPrimitivesForTesting in unit tests to avoid the friend
	// requirement.
	FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest,
	ScopedAllowBaseSyncPrimitivesOutsideBlockingScope);
	FRIEND_TEST_ALL_PREFIXES(
	ThreadRestrictionsTest,
	ScopedAllowBaseSyncPrimitivesOutsideBlockingScopeResetsState);
	friend class ::KeyStorageLinux;
	friend class content::SynchronousCompositor;
	friend class content::SynchronousCompositorHost;
	friend class content::SynchronousCompositorSyncCallBridge;
	friend class midi::TaskService; // https://crbug.com/796830
	// Not used in production yet, https://crbug.com/844078.
	friend class service_manager::ServiceProcessLauncher;
	friend class viz::HostGpuMemoryBufferManager;

	ScopedAllowBaseSyncPrimitivesOutsideBlockingScope()
	EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedAllowBaseSyncPrimitivesOutsideBlockingScope()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	#if DCHECK_IS_ON()
	const bool was_disallowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowBaseSyncPrimitivesOutsideBlockingScope);
	};

	// This can be used in tests without being a friend of
	// ScopedAllowBaseSyncPrimitives(OutsideBlockingScope).
	class BASE_EXPORT ScopedAllowBaseSyncPrimitivesForTesting {
	public:
	ScopedAllowBaseSyncPrimitivesForTesting() EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedAllowBaseSyncPrimitivesForTesting() EMPTY_BODY_IF_DCHECK_IS_OFF;

	private:
	#if DCHECK_IS_ON()
	const bool was_disallowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowBaseSyncPrimitivesForTesting);
	};

	namespace internal {

	// Asserts that waiting on a //base sync primitive is allowed in the current
	// scope.
	INLINE_IF_DCHECK_IS_OFF void AssertBaseSyncPrimitivesAllowed()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	// Resets all thread restrictions on the current thread.
	INLINE_IF_DCHECK_IS_OFF void ResetThreadRestrictionsForTesting()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	} // namespace internal

	// "Long CPU" work refers to any code that takes more than 100 ms to
	// run when there is no CPU contention and no hard page faults and therefore,
	// is not suitable to run on a thread required to keep the browser responsive
	// (where jank could be visible to the user).

	// Asserts that running long CPU work is allowed in the current scope.
	INLINE_IF_DCHECK_IS_OFF void AssertLongCPUWorkAllowed()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	// Disallows all tasks that may be unresponsive on the current thread. This
	// disallows blocking calls, waiting on a //base sync primitive and long CPU
	// work.
	INLINE_IF_DCHECK_IS_OFF void DisallowUnresponsiveTasks()
	EMPTY_BODY_IF_DCHECK_IS_OFF;

	class BASE_EXPORT ThreadRestrictions {
	public:
	// Constructing a ScopedAllowIO temporarily allows IO for the current
	// thread. Doing this is almost certainly always incorrect.
	//
	// DEPRECATED. Use ScopedAllowBlocking(ForTesting).
	class BASE_EXPORT ScopedAllowIO {
	public:
	ScopedAllowIO() EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedAllowIO() EMPTY_BODY_IF_DCHECK_IS_OFF;

	private:
	#if DCHECK_IS_ON()
	const bool was_allowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO);
	};

	#if DCHECK_IS_ON()
	// Set whether the current thread to make IO calls.
	// Threads start out in the allowed state.
	// Returns the previous value.
	//
	// DEPRECATED. Use ScopedAllowBlocking(ForTesting) or ScopedDisallowBlocking.
	static bool SetIOAllowed(bool allowed);

	// 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.
	//
	// DEPRECATED. Use DisallowBaseSyncPrimitives.
	static void DisallowWaiting();
	#if defined(STARBOARD)
	// Get whether the current thread can use singletons.
	static bool GetSingletonAllowed();
	#endif // defined(STARBOARD)
	#else
	// Inline the empty definitions of these functions so that they can be
	// compiled out.
	static bool SetIOAllowed(bool allowed) { return true; }
	static bool SetSingletonAllowed(bool allowed) { return true; }
	static void AssertSingletonAllowed() {}
	static void DisallowWaiting() {}
	#if defined(STARBOARD)
	// Get whether the current thread can use singletons.
	static bool GetSingletonAllowed() {return true;}
	#endif // defined(STARBOARD)
	#endif

	private:
	// DO NOT ADD ANY OTHER FRIEND STATEMENTS.
	// BEGIN ALLOWED USAGE.
	friend class android_webview::AwFormDatabaseService;
	friend class android_webview::CookieManager;
	friend class base::StackSamplingProfiler;
	friend class content::BrowserMainLoop;
	friend class content::BrowserShutdownProfileDumper;
	friend class content::BrowserTestBase;
	friend class content::NestedMessagePumpAndroid;
	friend class content::ScopedAllowWaitForAndroidLayoutTests;
	friend class content::ScopedAllowWaitForDebugURL;
	friend class ::HistogramSynchronizer;
	friend class internal::TaskTracker;
	friend class cc::CompletionEvent;
	friend class cc::SingleThreadTaskGraphRunner;
	friend class content::CategorizedWorkerPool;
	friend class remoting::AutoThread;
	friend class ui::WindowResizeHelperMac;
	friend class MessagePumpDefault;
	friend class SimpleThread;
	friend class Thread;
	friend class ThreadTestHelper;
	friend class PlatformThread;
	friend class android::JavaHandlerThread;
	friend class mojo::SyncCallRestrictions;
	friend class ui::CommandBufferClientImpl;
	friend class ui::CommandBufferLocal;
	friend class ui::GpuState;

	// END ALLOWED USAGE.
	// BEGIN USAGE THAT NEEDS TO BE FIXED.
	friend class ::chromeos::BlockingMethodCaller; // http://crbug.com/125360
	friend class ::chromeos::system::StatisticsProviderImpl; // http://crbug.com/125385
	friend class chrome_browser_net::Predictor; // http://crbug.com/78451
	friend class
	content::BrowserGpuChannelHostFactory; // http://crbug.com/125248
	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 gpu::GpuChannelHost; // http://crbug.com/125264
	friend class net::internal::AddressTrackerLinux; // http://crbug.com/125097
	friend class net::NetworkChangeNotifierMac; // http://crbug.com/125097
	friend class ::BrowserProcessImpl; // http://crbug.com/125207
	friend class ::NativeBackendKWallet; // http://crbug.com/125331
	#if !defined(OFFICIAL_BUILD)
	friend class content::SoftwareOutputDeviceMus; // Interim non-production code
	#endif
	// END USAGE THAT NEEDS TO BE FIXED.

	#if DCHECK_IS_ON()
	// DEPRECATED. Use ScopedAllowBaseSyncPrimitives.
	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.
	//
	// DEPRECATED. Use ScopedAllowBaseSyncPrimitives.
	class BASE_EXPORT ScopedAllowWait {
	public:
	ScopedAllowWait() EMPTY_BODY_IF_DCHECK_IS_OFF;
	~ScopedAllowWait() EMPTY_BODY_IF_DCHECK_IS_OFF;

	private:
	#if DCHECK_IS_ON()
	const bool was_allowed_;
	#endif

	DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
	};

	DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
	};

	} // namespace base

	#endif // BASE_THREADING_THREAD_RESTRICTIONS_H_