blob: 0ff11967128a70b5a7c87ed4e419718ec2d18c57 [file] [log] [blame]
// 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/macros.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 BrowserProcessImpl;
class HistogramSynchronizer;
class NativeBackendKWallet;
class ScopedAllowWaitForLegacyWebViewApi;
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 BrowserGpuMemoryBufferManager;
class BrowserShutdownProfileDumper;
class BrowserTestBase;
class NestedMessagePumpAndroid;
class ScopedAllowWaitForAndroidLayoutTests;
class ScopedAllowWaitForDebugURL;
class SoftwareOutputDeviceMus;
class TextInputClientMac;
class RasterWorkerPool;
} // namespace content
namespace dbus {
class Bus;
}
namespace disk_cache {
class BackendImpl;
class InFlightIO;
}
namespace gles2 {
class CommandBufferClientImpl;
}
namespace gpu {
class GpuChannelHost;
}
namespace mojo {
namespace common {
class MessagePumpMojo;
}
}
namespace mus {
class CommandBufferLocal;
class GpuState;
}
namespace net {
class NetworkChangeNotifierMac;
namespace internal {
class AddressTrackerLinux;
}
}
namespace remoting {
class AutoThread;
}
namespace ui {
class WindowResizeHelperMac;
}
namespace views {
class ScreenMus;
}
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::ScopedAllowWaitForAndroidLayoutTests;
friend class content::ScopedAllowWaitForDebugURL;
friend class ::HistogramSynchronizer;
friend class ::ScopedAllowWaitForLegacyWebViewApi;
friend class cc::CompletionEvent;
friend class cc::SingleThreadTaskGraphRunner;
friend class content::RasterWorkerPool;
friend class remoting::AutoThread;
friend class ui::WindowResizeHelperMac;
friend class MessagePumpDefault;
friend class SequencedWorkerPool;
friend class SimpleThread;
friend class Thread;
friend class ThreadTestHelper;
friend class PlatformThread;
friend class android::JavaHandlerThread;
friend class gles2::CommandBufferClientImpl;
friend class mojo::common::MessagePumpMojo;
friend class mus::CommandBufferLocal;
friend class mus::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::BrowserGpuMemoryBufferManager; // http://crbug.com/420368
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
friend class views::ScreenMus;
// 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_