base/threading/thread_restrictions.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_THREADING_THREAD_RESTRICTIONS_H_
   6 #define BASE_THREADING_THREAD_RESTRICTIONS_H_
   7
   8 #include "base/base_export.h"
   9 #include "base/basictypes.h"
  10
  11 // See comment at top of thread_checker.h
  12 #if (!defined(NDEBUG) || defined(DCHECK_ALWAYS_ON))
  13 #define ENABLE_THREAD_RESTRICTIONS 1
  14 #else
  15 #define ENABLE_THREAD_RESTRICTIONS 0
  16 #endif
  17
  18 class AcceleratedPresenter;
  19 class BrowserProcessImpl;
  20 class HistogramSynchronizer;
  21 class MetricsService;
  22 class NativeBackendKWallet;
  23 class ScopedAllowWaitForLegacyWebViewApi;
  24 class TestingAutomationProvider;
  25
  26 namespace browser_sync {
  27 class NonFrontendDataTypeController;
  28 class UIModelWorker;
  29 }
  30 namespace cc {
  31 class CompletionEvent;
  32 }
  33 namespace chromeos {
  34 class AudioMixerAlsa;
  35 class BlockingMethodCaller;
  36 namespace system {
  37 class StatisticsProviderImpl;
  38 }
  39 }
  40 namespace chrome_browser_net {
  41 class Predictor;
  42 }
  43 namespace content {
  44 class BrowserGpuChannelHostFactory;
  45 class BrowserShutdownProfileDumper;
  46 class BrowserTestBase;
  47 class GLHelper;
  48 class GpuChannelHost;
  49 class NestedMessagePumpAndroid;
  50 class RenderWidgetHelper;
  51 class ScopedAllowWaitForAndroidLayoutTests;
  52 class TextInputClientMac;
  53 }
  54 namespace dbus {
  55 class Bus;
  56 }
  57 namespace disk_cache {
  58 class BackendImpl;
  59 class InFlightIO;
  60 }
  61 namespace media {
  62 class AudioOutputController;
  63 }
  64 namespace net {
  65 class FileStreamPosix;
  66 class FileStreamWin;
  67 namespace internal {
  68 class AddressTrackerLinux;
  69 }
  70 }
  71
  72 namespace remoting {
  73 class AutoThread;
  74 }
  75
  76 namespace base {
  77
  78 namespace android {
  79 class JavaHandlerThread;
  80 }
  81
  82 class SequencedWorkerPool;
  83 class SimpleThread;
  84 class Thread;
  85 class ThreadTestHelper;
  86
  87 // Certain behavior is disallowed on certain threads.  ThreadRestrictions helps
  88 // enforce these rules.  Examples of such rules:
  89 //
  90 // * Do not do blocking IO (makes the thread janky)
  91 // * Do not access Singleton/LazyInstance (may lead to shutdown crashes)
  92 //
  93 // Here's more about how the protection works:
  94 //
  95 // 1) If a thread should not be allowed to make IO calls, mark it:
  96 //      base::ThreadRestrictions::SetIOAllowed(false);
  97 //    By default, threads *are* allowed to make IO calls.
  98 //    In Chrome browser code, IO calls should be proxied to the File thread.
  99 //
 100 // 2) If a function makes a call that will go out to disk, check whether the
 101 //    current thread is allowed:
 102 //      base::ThreadRestrictions::AssertIOAllowed();
 103 //
 104 //
 105 // Style tip: where should you put AssertIOAllowed checks?  It's best
 106 // if you put them as close to the disk access as possible, at the
 107 // lowest level.  This rule is simple to follow and helps catch all
 108 // callers.  For example, if your function GoDoSomeBlockingDiskCall()
 109 // only calls other functions in Chrome and not fopen(), you should go
 110 // add the AssertIOAllowed checks in the helper functions.
 111
 112 class BASE_EXPORT ThreadRestrictions {
 113  public:
 114   // Constructing a ScopedAllowIO temporarily allows IO for the current
 115   // thread.  Doing this is almost certainly always incorrect.
 116   class BASE_EXPORT ScopedAllowIO {
 117    public:
 118     ScopedAllowIO() { previous_value_ = SetIOAllowed(true); }
 119     ~ScopedAllowIO() { SetIOAllowed(previous_value_); }
 120    private:
 121     // Whether IO is allowed when the ScopedAllowIO was constructed.
 122     bool previous_value_;
 123
 124     DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO);
 125   };
 126
 127   // Constructing a ScopedAllowSingleton temporarily allows accessing for the
 128   // current thread.  Doing this is almost always incorrect.
 129   class BASE_EXPORT ScopedAllowSingleton {
 130    public:
 131     ScopedAllowSingleton() { previous_value_ = SetSingletonAllowed(true); }
 132     ~ScopedAllowSingleton() { SetSingletonAllowed(previous_value_); }
 133    private:
 134     // Whether singleton use is allowed when the ScopedAllowSingleton was
 135     // constructed.
 136     bool previous_value_;
 137
 138     DISALLOW_COPY_AND_ASSIGN(ScopedAllowSingleton);
 139   };
 140
 141 #if ENABLE_THREAD_RESTRICTIONS
 142   // Set whether the current thread to make IO calls.
 143   // Threads start out in the *allowed* state.
 144   // Returns the previous value.
 145   static bool SetIOAllowed(bool allowed);
 146
 147   // Check whether the current thread is allowed to make IO calls,
 148   // and DCHECK if not.  See the block comment above the class for
 149   // a discussion of where to add these checks.
 150   static void AssertIOAllowed();
 151
 152   // Set whether the current thread can use singletons.  Returns the previous
 153   // value.
 154   static bool SetSingletonAllowed(bool allowed);
 155
 156   // Check whether the current thread is allowed to use singletons (Singleton /
 157   // LazyInstance).  DCHECKs if not.
 158   static void AssertSingletonAllowed();
 159
 160   // Disable waiting on the current thread. Threads start out in the *allowed*
 161   // state. Returns the previous value.
 162   static void DisallowWaiting();
 163
 164   // Check whether the current thread is allowed to wait, and DCHECK if not.
 165   static void AssertWaitAllowed();
 166 #else
 167   // Inline the empty definitions of these functions so that they can be
 168   // compiled out.
 169   static bool SetIOAllowed(bool allowed) { return true; }
 170   static void AssertIOAllowed() {}
 171   static bool SetSingletonAllowed(bool allowed) { return true; }
 172   static void AssertSingletonAllowed() {}
 173   static void DisallowWaiting() {}
 174   static void AssertWaitAllowed() {}
 175 #endif
 176
 177  private:
 178   // DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to jam or brettw first.
 179   // BEGIN ALLOWED USAGE.
 180   friend class content::BrowserShutdownProfileDumper;
 181   friend class content::BrowserTestBase;
 182   friend class content::NestedMessagePumpAndroid;
 183   friend class content::RenderWidgetHelper;
 184   friend class content::ScopedAllowWaitForAndroidLayoutTests;
 185   friend class ::HistogramSynchronizer;
 186   friend class ::ScopedAllowWaitForLegacyWebViewApi;
 187   friend class ::TestingAutomationProvider;
 188   friend class cc::CompletionEvent;
 189   friend class remoting::AutoThread;
 190   friend class MessagePumpDefault;
 191   friend class SequencedWorkerPool;
 192   friend class SimpleThread;
 193   friend class Thread;
 194   friend class ThreadTestHelper;
 195   friend class PlatformThread;
 196   friend class android::JavaHandlerThread;
 197
 198   // END ALLOWED USAGE.
 199   // BEGIN USAGE THAT NEEDS TO BE FIXED.
 200   friend class ::chromeos::AudioMixerAlsa;        // http://crbug.com/125206
 201   friend class ::chromeos::BlockingMethodCaller;  // http://crbug.com/125360
 202   friend class ::chromeos::system::StatisticsProviderImpl;  // http://crbug.com/125385
 203   friend class browser_sync::NonFrontendDataTypeController;  // http://crbug.com/19757
 204   friend class browser_sync::UIModelWorker;       // http://crbug.com/19757
 205   friend class chrome_browser_net::Predictor;     // http://crbug.com/78451
 206   friend class
 207       content::BrowserGpuChannelHostFactory;      // http://crbug.com/125248
 208   friend class content::GLHelper;                 // http://crbug.com/125415
 209   friend class content::GpuChannelHost;           // http://crbug.com/125264
 210   friend class content::TextInputClientMac;       // http://crbug.com/121917
 211   friend class dbus::Bus;                         // http://crbug.com/125222
 212   friend class disk_cache::BackendImpl;           // http://crbug.com/74623
 213   friend class disk_cache::InFlightIO;            // http://crbug.com/74623
 214   friend class media::AudioOutputController;      // http://crbug.com/120973
 215   friend class net::FileStreamPosix;              // http://crbug.com/115067
 216   friend class net::FileStreamWin;                // http://crbug.com/115067
 217   friend class net::internal::AddressTrackerLinux;  // http://crbug.com/125097
 218   friend class ::AcceleratedPresenter;            // http://crbug.com/125391
 219   friend class ::BrowserProcessImpl;              // http://crbug.com/125207
 220   friend class ::MetricsService;                  // http://crbug.com/124954
 221   friend class ::NativeBackendKWallet;            // http://crbug.com/125331
 222   // END USAGE THAT NEEDS TO BE FIXED.
 223
 224 #if ENABLE_THREAD_RESTRICTIONS
 225   static bool SetWaitAllowed(bool allowed);
 226 #else
 227   static bool SetWaitAllowed(bool allowed) { return true; }
 228 #endif
 229
 230   // Constructing a ScopedAllowWait temporarily allows waiting on the current
 231   // thread.  Doing this is almost always incorrect, which is why we limit who
 232   // can use this through friend. If you find yourself needing to use this, find
 233   // another way. Talk to jam or brettw.
 234   class BASE_EXPORT ScopedAllowWait {
 235    public:
 236     ScopedAllowWait() { previous_value_ = SetWaitAllowed(true); }
 237     ~ScopedAllowWait() { SetWaitAllowed(previous_value_); }
 238    private:
 239     // Whether singleton use is allowed when the ScopedAllowWait was
 240     // constructed.
 241     bool previous_value_;
 242
 243     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
 244   };
 245
 246   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 247 };
 248
 249 }  // namespace base
 250
 251 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_