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// 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"
// -----------------------------------------------------------------------------
// Usage documentation
// -----------------------------------------------------------------------------
//
// Overview:
// This file exposes functions to ban and allow certain slow operations
// on a per-thread basis. To annotate *usage* of such slow operations, refer to
// scoped_blocking_call.h instead.
//
// Specific allowances that can be controlled in this file are:
// - 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.
//
// - Waiting on a //base sync primitive: Refers to calling one of these methods:
// - base::WaitableEvent::*Wait*
// - base::ConditionVariable::*Wait*
// - base::Process::WaitForExit*
//
// - 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).
//
// The following disallowance functions are offered:
// - DisallowBlocking(): Disallows blocking calls on the current thread.
// - DisallowBaseSyncPrimitives(): Disallows waiting on a //base sync primitive
// on the current thread.
// - DisallowUnresponsiveTasks() Disallows blocking calls, waiting on a //base
// sync primitive, and long cpu work on the current thread.
//
// In addition, scoped-allowance mechanisms are offered to make an exception
// within a scope for a behavior that is normally disallowed.
// - ScopedAllowBlocking(ForTesting): Allows blocking calls.
// - ScopedAllowBaseSyncPrimitives(ForTesting)(OutsideBlockingScope): Allow
// waiting on a //base sync primitive. The OutsideBlockingScope suffix allows
// uses in a scope where blocking is also disallowed.
//
// Avoid using allowances outside of unit tests. In unit tests, use allowances
// with the suffix "ForTesting".
//
// Prefer making blocking calls from tasks posted to base::ThreadPoolInstance
// with base::MayBlock().
//
// Instead of waiting on a WaitableEvent or a ConditionVariable, prefer putting
// the work that should happen after the wait in a continuation callback and
// post it 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.
//
// Where unavoidable, put ScopedAllow* instances in the narrowest scope possible
// in the caller making the blocking call but no further down. For example: 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 BrowserProcessImpl;
class HistogramSynchronizer;
class KeyStorageLinux;
class NativeBackendKWallet;
class NativeDesktopMediaList;
class StartupTimeBomb;
namespace android_webview {
class AwFormDatabaseService;
class CookieManager;
class ScopedAllowInitGLBindings;
class VizCompositorThreadRunnerWebView;
}
namespace audio {
class OutputDevice;
}
namespace blink {
class RTCVideoDecoderAdapter;
class RTCVideoEncoder;
class SourceStream;
class VideoFrameResourceProvider;
class WorkerThread;
namespace scheduler {
class WorkerThread;
}
}
namespace cc {
class CompletionEvent;
class TileTaskManagerImpl;
}
namespace chromeos {
class BlockingMethodCaller;
namespace system {
class StatisticsProviderImpl;
}
}
namespace chrome_browser_net {
class Predictor;
}
namespace chrome_cleaner {
class SystemReportComponent;
}
namespace content {
class BrowserGpuChannelHostFactory;
class BrowserMainLoop;
class BrowserProcessSubThread;
class BrowserShutdownProfileDumper;
class BrowserTestBase;
class CategorizedWorkerPool;
class DesktopCaptureDevice;
class InProcessUtilityThread;
class NestedMessagePumpAndroid;
class RenderProcessHostImpl;
class RenderWidgetHostViewMac;
class RTCVideoDecoder;
class SandboxHostLinux;
class ScopedAllowWaitForDebugURL;
class ServiceWorkerContextClient;
class SoftwareOutputDeviceMus;
class SynchronousCompositor;
class SynchronousCompositorHost;
class SynchronousCompositorSyncCallBridge;
class TextInputClientMac;
class WebContentsViewMac;
} // 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 history_report {
class HistoryReportJniBridge;
}
namespace gpu {
class GpuChannelHost;
}
namespace leveldb_env {
class DBTracker;
}
namespace media {
class AudioInputDevice;
class AudioOutputDevice;
class BlockingUrlProtocol;
class PaintCanvasVideoRenderer;
}
namespace memory_instrumentation {
class OSMetrics;
}
namespace midi {
}
namespace module_installer {
class ScopedAllowModulePakLoad;
}
namespace mojo {
class CoreLibraryInitializer;
class SyncCallRestrictions;
namespace core {
class ScopedIPCSupport;
}
}
namespace printing {
class PrintJobWorker;
class PrinterQuery;
}
namespace rlz_lib {
class FinancialPing;
}
namespace syncer {
class GetLocalChangesRequest;
class HttpBridge;
class ModelSafeWorker;
}
namespace ui {
class CommandBufferClientImpl;
class CommandBufferLocal;
class GpuState;
class MaterialDesignController;
}
namespace weblayer {
class WebLayerPathProvider;
}
namespace net {
class MultiThreadedCertVerifierScopedAllowBaseSyncPrimitives;
class MultiThreadedProxyResolverScopedAllowJoinOnIO;
class NetworkChangeNotifierMac;
class NetworkConfigWatcherMacThread;
namespace internal {
class AddressTrackerLinux;
}
}
namespace proxy_resolver {
class ScopedAllowThreadJoinForProxyResolverV8Tracing;
}
namespace remoting {
class AutoThread;
namespace protocol {
class ScopedAllowThreadJoinForWebRtcTransport;
}
}
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 vr {
class VrShell;
}
namespace web {
class WebMainLoop;
class WebSubThread;
}
namespace weblayer {
class ProfileImpl;
}
namespace webrtc {
class DesktopConfigurationMonitor;
}
namespace base {
namespace sequence_manager {
namespace internal {
class TaskQueueImpl;
}
} // namespace sequence_manager
namespace android {
class JavaHandlerThread;
}
namespace internal {
class JobTaskSource;
class TaskTracker;
}
class AdjustOOMScoreHelper;
class FileDescriptorWatcher;
class GetAppOutputScopedAllowBaseSyncPrimitives;
class ScopedAllowThreadRecallForStackSamplingProfiler;
class SimpleThread;
class StackSamplingProfiler;
class Thread;
#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
// The static_assert() eats follow-on semicolons. `= default` would work
// too, but it makes clang realize that all the Scoped classes are no-ops in
// non-dcheck builds and it starts emitting many -Wunused-variable warnings.
#define EMPTY_BODY_IF_DCHECK_IS_OFF \
{} \
static_assert(true, "")
#endif
namespace internal {
// Asserts that blocking calls are allowed in the current scope. This is an
// internal call, external code should use ScopedBlockingCall instead, which
// serves as a precise annotation of the scope that may/will block.
INLINE_IF_DCHECK_IS_OFF void AssertBlockingAllowed()
EMPTY_BODY_IF_DCHECK_IS_OFF;
} // namespace internal
// 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);
};
class BASE_EXPORT ScopedAllowBlocking {
private:
FRIEND_TEST_ALL_PREFIXES(ThreadRestrictionsTest, ScopedAllowBlocking);
friend class ScopedAllowBlockingForTesting;
// This can only be instantiated by friends. Use ScopedAllowBlockingForTesting
// in unit tests to avoid the friend requirement.
friend class AdjustOOMScoreHelper;
friend class android_webview::ScopedAllowInitGLBindings;
friend class content::BrowserProcessSubThread;
friend class content::WebContentsViewMac;
friend class cronet::CronetPrefsManager;
friend class cronet::CronetURLRequestContext;
friend class memory_instrumentation::OSMetrics;
friend class module_installer::ScopedAllowModulePakLoad;
friend class mojo::CoreLibraryInitializer;
friend class printing::PrintJobWorker;
friend class resource_coordinator::TabManagerDelegate; // crbug.com/778703
friend class ui::MaterialDesignController;
friend class web::WebSubThread;
friend class StackSamplingProfiler;
friend class weblayer::ProfileImpl;
friend class content::RenderProcessHostImpl;
friend class weblayer::WebLayerPathProvider;
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);
};
INLINE_IF_DCHECK_IS_OFF void DisallowBaseSyncPrimitives()
EMPTY_BODY_IF_DCHECK_IS_OFF;
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);
// Allowed usage:
friend class SimpleThread;
friend class base::GetAppOutputScopedAllowBaseSyncPrimitives;
friend class blink::SourceStream;
friend class blink::WorkerThread;
friend class blink::scheduler::WorkerThread;
friend class chrome_cleaner::SystemReportComponent;
friend class content::BrowserMainLoop;
friend class content::BrowserProcessSubThread;
friend class content::ServiceWorkerContextClient;
friend class functions::ExecScriptScopedAllowBaseSyncPrimitives;
friend class history_report::HistoryReportJniBridge;
friend class internal::TaskTracker;
friend class leveldb_env::DBTracker;
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 syncer::HttpBridge;
friend class syncer::GetLocalChangesRequest;
friend class syncer::ModelSafeWorker;
friend class webrtc::DesktopConfigurationMonitor;
// Usage that should be fixed:
friend class ::chromeos::system::
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);
};
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);
// Allowed usage:
friend class ::KeyStorageLinux;
friend class ::NativeDesktopMediaList;
friend class ::StartupTimeBomb;
friend class android::JavaHandlerThread;
friend class android_webview::
friend class android_webview::CookieManager;
friend class android_webview::VizCompositorThreadRunnerWebView;
friend class audio::OutputDevice;
friend class base::sequence_manager::internal::TaskQueueImpl;
friend class base::FileDescriptorWatcher;
friend class base::internal::JobTaskSource;
friend class base::ScopedAllowThreadRecallForStackSamplingProfiler;
friend class base::StackSamplingProfiler;
friend class blink::RTCVideoDecoderAdapter;
friend class blink::RTCVideoEncoder;
friend class cc::TileTaskManagerImpl;
friend class content::CategorizedWorkerPool;
friend class content::DesktopCaptureDevice;
friend class content::InProcessUtilityThread;
friend class content::RTCVideoDecoder;
friend class content::SandboxHostLinux;
friend class content::ScopedAllowWaitForDebugURL;
friend class content::SynchronousCompositor;
friend class content::SynchronousCompositorHost;
friend class content::SynchronousCompositorSyncCallBridge;
friend class media::AudioInputDevice;
friend class media::AudioOutputDevice;
friend class media::PaintCanvasVideoRenderer;
friend class mojo::SyncCallRestrictions;
friend class net::NetworkConfigWatcherMacThread;
friend class viz::HostGpuMemoryBufferManager;
friend class vr::VrShell;
// Usage that should be fixed:
friend class content::
friend class remoting::protocol::
friend class net::
friend class proxy_resolver::
friend class service_manager::ServiceProcessLauncher;
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);
};
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);
};
// Counterpart to base::DisallowUnresponsiveTasks() for tests to allow them to
// block their thread after it was banned.
class BASE_EXPORT ScopedAllowUnresponsiveTasksForTesting {
public:
ScopedAllowUnresponsiveTasksForTesting() EMPTY_BODY_IF_DCHECK_IS_OFF;
~ScopedAllowUnresponsiveTasksForTesting() EMPTY_BODY_IF_DCHECK_IS_OFF;
private:
#if DCHECK_IS_ON()
const bool was_disallowed_base_sync_;
const bool was_disallowed_blocking_;
const bool was_disallowed_cpu_;
#endif
DISALLOW_COPY_AND_ASSIGN(ScopedAllowUnresponsiveTasksForTesting);
};
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
// 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;
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();
#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() {}
#endif
private:
// DO NOT ADD ANY OTHER FRIEND STATEMENTS.
// BEGIN ALLOWED USAGE.
friend class content::BrowserMainLoop;
friend class content::BrowserShutdownProfileDumper;
friend class content::BrowserTestBase;
friend class content::ScopedAllowWaitForDebugURL;
friend class ::HistogramSynchronizer;
friend class internal::TaskTracker;
friend class web::WebMainLoop;
friend class MessagePumpDefault;
friend class PlatformThread;
friend class ui::CommandBufferClientImpl;
friend class ui::CommandBufferLocal;
friend class ui::GpuState;
// END ALLOWED USAGE.
// BEGIN USAGE THAT NEEDS TO BE FIXED.
#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
DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
};
#undef INLINE_IF_DCHECK_IS_OFF
#undef EMPTY_BODY_IF_DCHECK_IS_OFF
} // namespace base
#endif // BASE_THREADING_THREAD_RESTRICTIONS_H_