Dali 3D User Interface Engine
conditional-wait.cpp
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1 /*
2  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  *
16  */
17 
18 // CLASS HEADER
20 
21 // EXTERNAL INCLUDES
22 #include <pthread.h>
23 
24 // INTERNAL INCLUDES
27 
28 namespace Dali
29 {
30 
32 {
33  pthread_mutex_t mutex;
34  pthread_cond_t condition;
35  volatile unsigned int count;
36 };
37 
38 
40 {
42 }
43 
45 {
46  ConditionalWait& wait = mWait;
48 }
49 
52 {
53  if( pthread_mutex_init( &mImpl->mutex, NULL ) )
54  {
55  DALI_LOG_ERROR( "Unable to initialise mutex in ConditionalWait" );
56  }
57  if( pthread_cond_init( &mImpl->condition, NULL ) )
58  {
59  DALI_LOG_ERROR( "Unable to initialise conditional" );
60  }
61  mImpl->count = 0;
62 }
63 
65 {
66  if( pthread_cond_destroy( &mImpl->condition ) )
67  {
68  DALI_LOG_ERROR( "Unable to destroy conditional" );
69  }
70  if( pthread_mutex_destroy( &mImpl->mutex ) )
71  {
72  DALI_LOG_ERROR( "Unable to destroy mutex in ConditionalWait" );
73  }
74  delete mImpl;
75 }
76 
78 {
79  // pthread_cond_wait requires a lock to be held
81  volatile unsigned int previousCount = mImpl->count;
82  mImpl->count = 0; // change state before broadcast as that may wake clients immediately
83  // broadcast does nothing if the thread is not waiting but still has a system call overhead
84  // broadcast all threads to continue
85  if( 0 != previousCount )
86  {
87  if( pthread_cond_broadcast( &mImpl->condition ) )
88  {
89  DALI_LOG_ERROR( "Error calling pthread_cond_broadcast" );
90  }
91  }
93 }
94 
95 void ConditionalWait::Notify( const ScopedLock& scope )
96 {
97  // Scope must be locked:
98  DALI_ASSERT_DEBUG( &scope.GetLockedWait() == this );
99 
100  volatile unsigned int previousCount = mImpl->count;
101  mImpl->count = 0; // change state before broadcast as that may wake clients immediately
102  // broadcast does nothing if the thread is not waiting but still has a system call overhead
103  // broadcast all threads to continue
104  if( 0 != previousCount )
105  {
106  if( pthread_cond_broadcast( &mImpl->condition ) )
107  {
108  DALI_LOG_ERROR( "Error calling pthread_cond_broadcast" );
109  }
110  }
111 }
112 
114 {
115  // pthread_cond_wait requires a lock to be held
117  ++(mImpl->count);
118  // pthread_cond_wait may wake up without anyone calling Notify
119  do
120  {
121  // wait while condition changes
122  if( pthread_cond_wait( &mImpl->condition, &mImpl->mutex ) ) // releases the lock whilst waiting
123  {
124  DALI_LOG_ERROR( "Error calling pthread_cond_wait" );
125  break;
126  }
127  }
128  while( 0 != mImpl->count );
129  // when condition returns the mutex is locked so release the lock
131 }
132 
133 void ConditionalWait::Wait( const ScopedLock& scope )
134 {
135  // Scope must be locked:
136  DALI_ASSERT_DEBUG( &scope.GetLockedWait() == this );
137 
138  ++(mImpl->count);
139 
140  // pthread_cond_wait may wake up without anyone calling Notify so loop until
141  // count has been reset in a notify:
142  do
143  {
144  // wait while condition changes
145  if( pthread_cond_wait( &mImpl->condition, &mImpl->mutex ) ) // releases the lock whilst waiting
146  {
147  DALI_LOG_ERROR( "Error calling pthread_cond_wait" );
148  break;
149  }
150  }
151  while( 0 != mImpl->count );
152 
153  // We return with our mutex locked safe in the knowledge that the ScopedLock
154  // passed in will unlock it in the caller.
155 }
156 
157 unsigned int ConditionalWait::GetWaitCount() const
158 {
159  return mImpl->count;
160 }
161 
162 } // namespace Dali
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