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 RenderWidgetResizeHelper;
  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 mojo {
  65 namespace common {
  66 class WatcherThreadManager;
  67 }
  68 }
  69 namespace net {
  70 class FileStreamPosix;
  71 class FileStreamWin;
  72 namespace internal {
  73 class AddressTrackerLinux;
  74 }
  75 }
  76
  77 namespace remoting {
  78 class AutoThread;
  79 }
  80
  81 namespace base {
  82
  83 namespace android {
  84 class JavaHandlerThread;
  85 }
  86
  87 class SequencedWorkerPool;
  88 class SimpleThread;
  89 class Thread;
  90 class ThreadTestHelper;
  91
  92 // Certain behavior is disallowed on certain threads.  ThreadRestrictions helps
  93 // enforce these rules.  Examples of such rules:
  94 //
  95 // * Do not do blocking IO (makes the thread janky)
  96 // * Do not access Singleton/LazyInstance (may lead to shutdown crashes)
  97 //
  98 // Here's more about how the protection works:
  99 //
 100 // 1) If a thread should not be allowed to make IO calls, mark it:
 101 //      base::ThreadRestrictions::SetIOAllowed(false);
 102 //    By default, threads *are* allowed to make IO calls.
 103 //    In Chrome browser code, IO calls should be proxied to the File thread.
 104 //
 105 // 2) If a function makes a call that will go out to disk, check whether the
 106 //    current thread is allowed:
 107 //      base::ThreadRestrictions::AssertIOAllowed();
 108 //
 109 //
 110 // Style tip: where should you put AssertIOAllowed checks?  It's best
 111 // if you put them as close to the disk access as possible, at the
 112 // lowest level.  This rule is simple to follow and helps catch all
 113 // callers.  For example, if your function GoDoSomeBlockingDiskCall()
 114 // only calls other functions in Chrome and not fopen(), you should go
 115 // add the AssertIOAllowed checks in the helper functions.
 116
 117 class BASE_EXPORT ThreadRestrictions {
 118  public:
 119   // Constructing a ScopedAllowIO temporarily allows IO for the current
 120   // thread.  Doing this is almost certainly always incorrect.
 121   class BASE_EXPORT ScopedAllowIO {
 122    public:
 123     ScopedAllowIO() { previous_value_ = SetIOAllowed(true); }
 124     ~ScopedAllowIO() { SetIOAllowed(previous_value_); }
 125    private:
 126     // Whether IO is allowed when the ScopedAllowIO was constructed.
 127     bool previous_value_;
 128
 129     DISALLOW_COPY_AND_ASSIGN(ScopedAllowIO);
 130   };
 131
 132   // Constructing a ScopedAllowSingleton temporarily allows accessing for the
 133   // current thread.  Doing this is almost always incorrect.
 134   class BASE_EXPORT ScopedAllowSingleton {
 135    public:
 136     ScopedAllowSingleton() { previous_value_ = SetSingletonAllowed(true); }
 137     ~ScopedAllowSingleton() { SetSingletonAllowed(previous_value_); }
 138    private:
 139     // Whether singleton use is allowed when the ScopedAllowSingleton was
 140     // constructed.
 141     bool previous_value_;
 142
 143     DISALLOW_COPY_AND_ASSIGN(ScopedAllowSingleton);
 144   };
 145
 146 #if ENABLE_THREAD_RESTRICTIONS
 147   // Set whether the current thread to make IO calls.
 148   // Threads start out in the *allowed* state.
 149   // Returns the previous value.
 150   static bool SetIOAllowed(bool allowed);
 151
 152   // Check whether the current thread is allowed to make IO calls,
 153   // and DCHECK if not.  See the block comment above the class for
 154   // a discussion of where to add these checks.
 155   static void AssertIOAllowed();
 156
 157   // Set whether the current thread can use singletons.  Returns the previous
 158   // value.
 159   static bool SetSingletonAllowed(bool allowed);
 160
 161   // Check whether the current thread is allowed to use singletons (Singleton /
 162   // LazyInstance).  DCHECKs if not.
 163   static void AssertSingletonAllowed();
 164
 165   // Disable waiting on the current thread. Threads start out in the *allowed*
 166   // state. Returns the previous value.
 167   static void DisallowWaiting();
 168
 169   // Check whether the current thread is allowed to wait, and DCHECK if not.
 170   static void AssertWaitAllowed();
 171 #else
 172   // Inline the empty definitions of these functions so that they can be
 173   // compiled out.
 174   static bool SetIOAllowed(bool allowed) { return true; }
 175   static void AssertIOAllowed() {}
 176   static bool SetSingletonAllowed(bool allowed) { return true; }
 177   static void AssertSingletonAllowed() {}
 178   static void DisallowWaiting() {}
 179   static void AssertWaitAllowed() {}
 180 #endif
 181
 182  private:
 183   // DO NOT ADD ANY OTHER FRIEND STATEMENTS, talk to jam or brettw first.
 184   // BEGIN ALLOWED USAGE.
 185   friend class content::BrowserShutdownProfileDumper;
 186   friend class content::BrowserTestBase;
 187   friend class content::NestedMessagePumpAndroid;
 188   friend class content::RenderWidgetResizeHelper;
 189   friend class content::ScopedAllowWaitForAndroidLayoutTests;
 190   friend class ::HistogramSynchronizer;
 191   friend class ::ScopedAllowWaitForLegacyWebViewApi;
 192   friend class ::TestingAutomationProvider;
 193   friend class cc::CompletionEvent;
 194   friend class mojo::common::WatcherThreadManager;
 195   friend class remoting::AutoThread;
 196   friend class MessagePumpDefault;
 197   friend class SequencedWorkerPool;
 198   friend class SimpleThread;
 199   friend class Thread;
 200   friend class ThreadTestHelper;
 201   friend class PlatformThread;
 202   friend class android::JavaHandlerThread;
 203
 204   // END ALLOWED USAGE.
 205   // BEGIN USAGE THAT NEEDS TO BE FIXED.
 206   friend class ::chromeos::AudioMixerAlsa;        // http://crbug.com/125206
 207   friend class ::chromeos::BlockingMethodCaller;  // http://crbug.com/125360
 208   friend class ::chromeos::system::StatisticsProviderImpl;  // http://crbug.com/125385
 209   friend class browser_sync::NonFrontendDataTypeController;  // http://crbug.com/19757
 210   friend class browser_sync::UIModelWorker;       // http://crbug.com/19757
 211   friend class chrome_browser_net::Predictor;     // http://crbug.com/78451
 212   friend class
 213       content::BrowserGpuChannelHostFactory;      // http://crbug.com/125248
 214   friend class content::GLHelper;                 // http://crbug.com/125415
 215   friend class content::GpuChannelHost;           // http://crbug.com/125264
 216   friend class content::TextInputClientMac;       // http://crbug.com/121917
 217   friend class dbus::Bus;                         // http://crbug.com/125222
 218   friend class disk_cache::BackendImpl;           // http://crbug.com/74623
 219   friend class disk_cache::InFlightIO;            // http://crbug.com/74623
 220   friend class media::AudioOutputController;      // http://crbug.com/120973
 221   friend class net::FileStreamPosix;              // http://crbug.com/115067
 222   friend class net::FileStreamWin;                // http://crbug.com/115067
 223   friend class net::internal::AddressTrackerLinux;  // http://crbug.com/125097
 224   friend class ::AcceleratedPresenter;            // http://crbug.com/125391
 225   friend class ::BrowserProcessImpl;              // http://crbug.com/125207
 226   friend class ::MetricsService;                  // http://crbug.com/124954
 227   friend class ::NativeBackendKWallet;            // http://crbug.com/125331
 228   // END USAGE THAT NEEDS TO BE FIXED.
 229
 230 #if ENABLE_THREAD_RESTRICTIONS
 231   static bool SetWaitAllowed(bool allowed);
 232 #else
 233   static bool SetWaitAllowed(bool allowed) { return true; }
 234 #endif
 235
 236   // Constructing a ScopedAllowWait temporarily allows waiting on the current
 237   // thread.  Doing this is almost always incorrect, which is why we limit who
 238   // can use this through friend. If you find yourself needing to use this, find
 239   // another way. Talk to jam or brettw.
 240   class BASE_EXPORT ScopedAllowWait {
 241    public:
 242     ScopedAllowWait() { previous_value_ = SetWaitAllowed(true); }
 243     ~ScopedAllowWait() { SetWaitAllowed(previous_value_); }
 244    private:
 245     // Whether singleton use is allowed when the ScopedAllowWait was
 246     // constructed.
 247     bool previous_value_;
 248
 249     DISALLOW_COPY_AND_ASSIGN(ScopedAllowWait);
 250   };
 251
 252   DISALLOW_IMPLICIT_CONSTRUCTORS(ThreadRestrictions);
 253 };
 254
 255 }  // namespace base
 256
 257 #endif  // BASE_THREADING_THREAD_RESTRICTIONS_H_