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author | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2012-09-17 18:18:44 +0000 |
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committer | patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3> | 2012-09-17 18:18:44 +0000 |
commit | 57623d42ebb04f0a0b9e6eb7c0847a3ece2aa0ff (patch) | |
tree | 25d07d14e920d31c0b1947c9ca586f2a01fc32d8 /nuttx/sched/pthread_barrierwait.c | |
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Resync new repository with old repo r5166
git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5153 42af7a65-404d-4744-a932-0658087f49c3
Diffstat (limited to 'nuttx/sched/pthread_barrierwait.c')
-rw-r--r-- | nuttx/sched/pthread_barrierwait.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/nuttx/sched/pthread_barrierwait.c b/nuttx/sched/pthread_barrierwait.c new file mode 100644 index 000000000..8ca8d1754 --- /dev/null +++ b/nuttx/sched/pthread_barrierwait.c @@ -0,0 +1,182 @@ +/******************************************************************************** + * sched/pthread_barrierwait.c + * + * Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ********************************************************************************/ + +/******************************************************************************** + * Included Files + ********************************************************************************/ + +#include <nuttx/config.h> + +#include <pthread.h> +#include <semaphore.h> +#include <sched.h> +#include <errno.h> +#include <debug.h> + +/******************************************************************************** + * Definitions + ********************************************************************************/ + +/******************************************************************************** + * Private Type Declarations + ********************************************************************************/ + +/******************************************************************************** + * Global Variables + ********************************************************************************/ + +/******************************************************************************** + * Private Variables + ********************************************************************************/ + +/******************************************************************************** + * Private Function Prototypes + ********************************************************************************/ + +/******************************************************************************** + * Public Functions + ********************************************************************************/ + +/******************************************************************************** + * Name: pthread_barrier_wait + * + * Description: + * The pthread_barrier_wait() function synchronizse participating threads at + * the barrier referenced by 'barrier'. The calling thread is blocked until + * the required number of threads have called pthread_barrier_wait() specifying + * the same 'barrier'. When the required number of threads have called + * pthread_barrier_wait() specifying the 'barrier', the constant + * PTHREAD_BARRIER_SERIAL_THREAD will be returned to one unspecified thread + * and zero will be returned to each of the remaining threads. At this point, + * the barrier will be reset to the state it had as a result of the most recent + * pthread_barrier_init() function that referenced it. + * + * The constant PTHREAD_BARRIER_SERIAL_THREAD is defined in pthread.h and its + * value must be distinct from any other value returned by pthread_barrier_wait(). + * + * The results are undefined if this function is called with an uninitialized + * barrier. + * + * If a signal is delivered to a thread blocked on a barrier, upon return from + * the signal handler the thread will resume waiting at the barrier if the barrier + * wait has not completed; otherwise, the thread will continue as normal from + * the completed barrier wait. Until the thread in the signal handler returns + * from it, it is unspecified whether other threads may proceed past the barrier + * once they have all reached it. + * + * A thread that has blocked on a barrier will not prevent any unblocked thread + * that is eligible to use the same processing resources from eventually making + * forward progress in its execution. Eligibility for processing resources will + * be determined by the scheduling policy. + * + * Parameters: + * barrier - the barrier to wait on + * + * Return Value: + * 0 (OK) on success or EINVAL if the barrier is not valid. + * + * Assumptions: + * + ********************************************************************************/ + +int pthread_barrier_wait(FAR pthread_barrier_t *barrier) +{ + int semcount; + int ret = OK; + + if (!barrier) + { + return EINVAL; + } + + /* Disable pre-emption throughout the following */ + + sched_lock(); + + /* Find out how many threads are already waiting at the barrier */ + + ret = sem_getvalue(&barrier->sem, &semcount); + if (ret != OK) + { + sched_unlock(); + return EINVAL; + } + + /* If the number of waiters would be equal to the count, then we are done */ + + if (1 - semcount >= barrier->count) + { + /* Free all of the waiting threads */ + + while (semcount < 0) + { + (void)sem_post(&barrier->sem); + (void)sem_getvalue(&barrier->sem, &semcount); + } + + /* Then return PTHREAD_BARRIER_SERIAL_THREAD to the final thread */ + + sched_unlock(); + return PTHREAD_BARRIER_SERIAL_THREAD; + } + else + { + /* Otherwise, this thread must wait as well */ + + while (sem_wait(&barrier->sem) != OK) + { + /* If the thread is awakened by a signal, just continue to wait */ + + int errornumber = get_errno(); + if (errornumber != EINTR) + { + /* If it is awakened by some other error, then there is a + * problem + */ + + sched_unlock(); + return errornumber; + } + } + + /* We will only get here when we are one of the N-1 threads that were + * waiting for the final thread at the barrier. We just need to return + * zero. + */ + + sched_unlock(); + return 0; + } +} |