1 #ifndef _DESPINBARRIER_HPP
2 #define _DESPINBARRIER_HPP
3 /*-------------------------------------------------------------------------
4 * drawElements C++ Base Library
5 * -----------------------------
7 * Copyright 2015 The Android Open Source Project
9 * Licensed under the Apache License, Version 2.0 (the "License");
10 * you may not use this file except in compliance with the License.
11 * You may obtain a copy of the License at
13 * http://www.apache.org/licenses/LICENSE-2.0
15 * Unless required by applicable law or agreed to in writing, software
16 * distributed under the License is distributed on an "AS IS" BASIS,
17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
18 * See the License for the specific language governing permissions and
19 * limitations under the License.
23 * \brief Cross-thread barrier.
24 *//*--------------------------------------------------------------------*/
32 /*--------------------------------------------------------------------*//*!
33 * \brief Cross-thread barrier
35 * SpinBarrier provides barrier implementation that uses spin loop for
36 * waiting for other threads. Threads may choose to wait in tight loop
37 * (WAIT_MODE_BUSY) or yield between iterations (WAIT_MODE_YIELD).
39 * It is not recommended to use WAIT_MODE_BUSY when there are more threads
40 * than number of cores participating in the barrier as it will lead to
41 * priority inversion and dramatic slowdown. For that reason WAIT_MODE_AUTO
42 * is provided, which selects between busy and yielding waiting based on
44 *//*--------------------------------------------------------------------*/
50 WAIT_MODE_BUSY = 0, //! Wait in tight spin loop.
51 WAIT_MODE_YIELD, //! Call deYield() between spin loop iterations.
52 WAIT_MODE_AUTO, //! Use WAIT_MODE_BUSY loop if #threads <= #cores, otherwise WAIT_MODE_YIELD.
57 SpinBarrier (deInt32 numThreads);
60 //! Reset barrier. Not thread-safe, e.g. no other thread can
61 //! be calling sync() or removeThread() at the same time.
62 void reset (deUint32 numThreads);
64 //! Wait until all threads (determined by active thread count)
65 //! have entered sync().
66 void sync (WaitMode mode);
68 //! Remove thread from barrier (decrements active thread count).
69 //! Can be called concurrently with sync() or removeThread().
70 void removeThread (WaitMode mode);
73 SpinBarrier (const SpinBarrier&);
74 SpinBarrier operator= (const SpinBarrier&);
76 const deUint32 m_numCores;
78 volatile deInt32 m_numThreads;
79 volatile deInt32 m_numEntered;
80 volatile deInt32 m_numLeaving;
81 volatile deInt32 m_numRemoved;
84 void SpinBarrier_selfTest (void);
88 #endif // _DESPINBARRIER_HPP