ppapi/shared_impl/tracked_callback.cc

   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 #include "ppapi/shared_impl/tracked_callback.h"
   6
   7 #include "base/bind.h"
   8 #include "base/compiler_specific.h"
   9 #include "base/logging.h"
  10 #include "base/message_loop/message_loop.h"
  11 #include "base/synchronization/lock.h"
  12 #include "ppapi/c/pp_completion_callback.h"
  13 #include "ppapi/c/pp_errors.h"
  14 #include "ppapi/c/ppb_message_loop.h"
  15 #include "ppapi/shared_impl/callback_tracker.h"
  16 #include "ppapi/shared_impl/ppapi_globals.h"
  17 #include "ppapi/shared_impl/ppb_message_loop_shared.h"
  18 #include "ppapi/shared_impl/proxy_lock.h"
  19 #include "ppapi/shared_impl/resource.h"
  20
  21 namespace ppapi {
  22
  23 namespace {
  24
  25 bool IsMainThread() {
  26   return PpapiGlobals::Get()
  27       ->GetMainThreadMessageLoop()
  28       ->BelongsToCurrentThread();
  29 }
  30
  31 int32_t RunCompletionTask(TrackedCallback::CompletionTask completion_task,
  32                           int32_t result) {
  33   int32_t task_result = completion_task.Run(result);
  34   if (result != PP_ERROR_ABORTED)
  35     result = task_result;
  36   return result;
  37 }
  38
  39 }  // namespace
  40
  41 // TrackedCallback -------------------------------------------------------------
  42
  43 // Note: don't keep a Resource* since it may go out of scope before us.
  44 TrackedCallback::TrackedCallback(Resource* resource,
  45                                  const PP_CompletionCallback& callback)
  46     : is_scheduled_(false),
  47       resource_id_(resource ? resource->pp_resource() : 0),
  48       completed_(false),
  49       aborted_(false),
  50       callback_(callback),
  51       target_loop_(PpapiGlobals::Get()->GetCurrentMessageLoop()),
  52       result_for_blocked_callback_(PP_OK) {
  53   // Note that target_loop_ may be NULL at this point, if the plugin has not
  54   // attached a loop to this thread, or if this is an in-process plugin.
  55   // The Enter class should handle checking this for us.
  56
  57   // TODO(dmichael): Add tracking at the instance level, for callbacks that only
  58   // have an instance (e.g. for MouseLock).
  59   if (resource) {
  60     tracker_ = PpapiGlobals::Get()->GetCallbackTrackerForInstance(
  61         resource->pp_instance());
  62     tracker_->Add(make_scoped_refptr(this));
  63   }
  64
  65   base::Lock* proxy_lock = ProxyLock::Get();
  66   if (proxy_lock) {
  67     // If the proxy_lock is valid, we're running out-of-process, and locking
  68     // is enabled.
  69     if (is_blocking()) {
  70       // This is a blocking completion callback, so we will need a condition
  71       // variable for blocking & signalling the calling thread.
  72       operation_completed_condvar_.reset(
  73           new base::ConditionVariable(proxy_lock));
  74     } else {
  75       // It's a non-blocking callback, so we should have a MessageLoopResource
  76       // to dispatch to. Note that we don't error check here, though. Later,
  77       // EnterResource::SetResult will check to make sure the callback is valid
  78       // and take appropriate action.
  79     }
  80   }
  81 }
  82
  83 TrackedCallback::~TrackedCallback() {}
  84
  85 void TrackedCallback::Abort() { Run(PP_ERROR_ABORTED); }
  86
  87 void TrackedCallback::PostAbort() { PostRun(PP_ERROR_ABORTED); }
  88
  89 void TrackedCallback::Run(int32_t result) {
  90   // Only allow the callback to be run once. Note that this also covers the case
  91   // where the callback was previously Aborted because its associated Resource
  92   // went away. The callback may live on for a while because of a reference from
  93   // a Closure. But when the Closure runs, Run() quietly does nothing, and the
  94   // callback will go away when all referring Closures go away.
  95   if (completed())
  96     return;
  97   if (result == PP_ERROR_ABORTED)
  98     aborted_ = true;
  99
 100   // Note that this call of Run() may have been scheduled prior to Abort() or
 101   // PostAbort() being called. If we have been told to Abort, that always
 102   // trumps a result that was scheduled before, so we should make sure to pass
 103   // PP_ERROR_ABORTED.
 104   if (aborted())
 105     result = PP_ERROR_ABORTED;
 106
 107   if (is_blocking()) {
 108     // If the condition variable is invalid, there are two possibilities. One,
 109     // we're running in-process, in which case the call should have come in on
 110     // the main thread and we should have returned PP_ERROR_BLOCKS_MAIN_THREAD
 111     // well before this. Otherwise, this callback was not created as a
 112     // blocking callback. Either way, there's some internal error.
 113     if (!operation_completed_condvar_.get()) {
 114       NOTREACHED();
 115       return;
 116     }
 117     result_for_blocked_callback_ = result;
 118     // Retain ourselves, since MarkAsCompleted will remove us from the
 119     // tracker. Then MarkAsCompleted before waking up the blocked thread,
 120     // which could potentially re-enter.
 121     scoped_refptr<TrackedCallback> thiz(this);
 122     MarkAsCompleted();
 123     // Wake up the blocked thread. See BlockUntilComplete for where the thread
 124     // Wait()s.
 125     operation_completed_condvar_->Signal();
 126   } else {
 127     // If there's a target_loop_, and we're not on the right thread, we need to
 128     // post to target_loop_.
 129     if (target_loop_.get() &&
 130         target_loop_.get() != PpapiGlobals::Get()->GetCurrentMessageLoop()) {
 131       PostRun(result);
 132       return;
 133     }
 134
 135     // Copy callback fields now, since |MarkAsCompleted()| may delete us.
 136     PP_CompletionCallback callback = callback_;
 137     CompletionTask completion_task = completion_task_;
 138     completion_task_.Reset();
 139     // Do this before running the callback in case of reentrancy from running
 140     // the completion task.
 141     MarkAsCompleted();
 142
 143     if (!completion_task.is_null())
 144       result = RunCompletionTask(completion_task, result);
 145
 146     // TODO(dmichael): Associate a message loop with the callback; if it's not
 147     // the same as the current thread's loop, then post it to the right loop.
 148     CallWhileUnlocked(PP_RunCompletionCallback, &callback, result);
 149   }
 150 }
 151
 152 void TrackedCallback::PostRun(int32_t result) {
 153   if (completed()) {
 154     NOTREACHED();
 155     return;
 156   }
 157   if (result == PP_ERROR_ABORTED)
 158     aborted_ = true;
 159   // We might abort when there's already a scheduled callback, but callers
 160   // should never try to PostRun more than once otherwise.
 161   DCHECK(result == PP_ERROR_ABORTED || !is_scheduled_);
 162
 163   if (is_blocking()) {
 164     // We might not have a MessageLoop to post to, so we must call Run()
 165     // directly.
 166     Run(result);
 167   } else {
 168     base::Closure callback_closure(
 169         RunWhileLocked(base::Bind(&TrackedCallback::Run, this, result)));
 170     if (target_loop_) {
 171       target_loop_->PostClosure(FROM_HERE, callback_closure, 0);
 172     } else {
 173       // We must be running in-process and on the main thread (the Enter
 174       // classes protect against having a null target_loop_ otherwise).
 175       DCHECK(IsMainThread());
 176       DCHECK(PpapiGlobals::Get()->IsHostGlobals());
 177       base::MessageLoop::current()->PostTask(FROM_HERE, callback_closure);
 178     }
 179   }
 180   is_scheduled_ = true;
 181 }
 182
 183 void TrackedCallback::set_completion_task(
 184     const CompletionTask& completion_task) {
 185   DCHECK(completion_task_.is_null());
 186   completion_task_ = completion_task;
 187 }
 188
 189 // static
 190 bool TrackedCallback::IsPending(
 191     const scoped_refptr<TrackedCallback>& callback) {
 192   if (!callback.get())
 193     return false;
 194   if (callback->aborted())
 195     return false;
 196   return !callback->completed();
 197 }
 198
 199 // static
 200 bool TrackedCallback::IsScheduledToRun(
 201     const scoped_refptr<TrackedCallback>& callback) {
 202   return IsPending(callback) && callback->is_scheduled_;
 203 }
 204
 205 int32_t TrackedCallback::BlockUntilComplete() {
 206   // Note, we are already holding the proxy lock in all these methods, including
 207   // this one (see ppapi/thunk/enter.cc for where it gets acquired).
 208
 209   // It doesn't make sense to wait on a non-blocking callback. Furthermore,
 210   // BlockUntilComplete should never be called for in-process plugins, where
 211   // blocking callbacks are not supported.
 212   CHECK(operation_completed_condvar_.get());
 213   if (!is_blocking() || !operation_completed_condvar_.get()) {
 214     NOTREACHED();
 215     return PP_ERROR_FAILED;
 216   }
 217
 218   while (!completed())
 219     operation_completed_condvar_->Wait();
 220
 221   if (!completion_task_.is_null()) {
 222     result_for_blocked_callback_ =
 223         RunCompletionTask(completion_task_, result_for_blocked_callback_);
 224     completion_task_.Reset();
 225   }
 226   return result_for_blocked_callback_;
 227 }
 228
 229 void TrackedCallback::MarkAsCompleted() {
 230   DCHECK(!completed());
 231
 232   // We will be removed; maintain a reference to ensure we won't be deleted
 233   // until we're done.
 234   scoped_refptr<TrackedCallback> thiz = this;
 235   completed_ = true;
 236   // We may not have a valid resource, in which case we're not in the tracker.
 237   if (resource_id_)
 238     tracker_->Remove(thiz);
 239   tracker_ = NULL;
 240 }
 241
 242 }  // namespace ppapi