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      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
    243