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Diffstat (limited to 'nuttx/sched/pthread_join.c')
-rw-r--r-- | nuttx/sched/pthread_join.c | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/nuttx/sched/pthread_join.c b/nuttx/sched/pthread_join.c new file mode 100644 index 000000000..6a02af352 --- /dev/null +++ b/nuttx/sched/pthread_join.c @@ -0,0 +1,248 @@ +/**************************************************************************** + * pthread_join.c + * + * Copyright (C) 2007, 2008, 2011 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 <sys/types.h> +#include <unistd.h> +#include <pthread.h> +#include <errno.h> +#include <debug.h> + +#include "os_internal.h" +#include "pthread_internal.h" + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Type Declarations + ****************************************************************************/ + +/**************************************************************************** + * Global Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: pthread_join + * + * Description: + * A thread can await termination of another thread and retrieve the + * return value of the thread. + * + * Parameters: + * thread + * pexit_value + * + * Return Value: + * 0 if successful. Otherwise, one of the following error codes: + * + * EINVAL The value specified by thread does not refer to ajoinable + * thread. + * ESRCH No thread could be found corresponding to thatspecified by the + * given thread ID. + * EDEADLK A deadlock was detected or the value of thread specifies the + * calling thread. + * + * Assumptions: + * + ****************************************************************************/ + +int pthread_join(pthread_t thread, FAR pthread_addr_t *pexit_value) +{ + FAR join_t *pjoin; + int ret; + + sdbg("thread=%d\n", thread); + + /* First make sure that this is not an attempt to join to + * ourself. + */ + + if ((pid_t)thread == getpid()) + { + return EDEADLK; + } + + /* Make sure no other task is mucking with the data structures + * while we are performing the following operations. NOTE: + * we can be also sure that pthread_exit() will not execute + * because it will also attempt to get this semaphore. + */ + + (void)pthread_takesemaphore(&g_join_semaphore); + + /* Find the join information associated with this thread. + * This can fail for one of three reasons: (1) There is no + * thread associated with 'thread,' (2) the thread is a task + * and does not have join information, or (3) the thread + * was detached and has exitted. + */ + + pjoin = pthread_findjoininfo((pid_t)thread); + if (!pjoin) + { + /* Determine what kind of error to return */ + + FAR _TCB *tcb = sched_gettcb((pthread_t)thread); + + sdbg("Could not find thread data\n"); + + /* Case (1) or (3) -- we can't tell which. Assume (3) */ + + if (!tcb) + { + ret = ESRCH; + } + + /* The thread is still active but has no join info. In that + * case, it must be a task and not a pthread. + */ + + else + { + ret = EINVAL; + } + + (void)pthread_givesemaphore(&g_join_semaphore); + } + else + { + /* We found the join info structure. Increment for the reference + * to the join structure that we have. This will keep things + * stable for we have to do + */ + + sched_lock(); + pjoin->crefs++; + + /* Check if the thread is still running. If not, then things are + * simpler. There are still race conditions to be concerned with. + * For example, there could be multiple threads executing in the + * 'else' block below when we enter! + */ + + if (pjoin->terminated) + { + sdbg("Thread has terminated\n"); + + /* Get the thread exit value from the terminated thread. */ + + if (pexit_value) + { + sdbg("exit_value=0x%p\n", pjoin->exit_value); + *pexit_value = pjoin->exit_value; + } + } + else + { + sdbg("Thread is still running\n"); + + /* Relinquish the data set semaphore. Since pre-emption is + * disabled, we can be certain that no task has the + * opportunity to run between the time we relinquish the + * join semaphore and the time that we wait on the thread exit + * semaphore. + */ + + (void)pthread_givesemaphore(&g_join_semaphore); + + /* Take the thread's thread exit semaphore. We will sleep here + * until the thread exits. We need to exercise caution because + * there could be multiple threads waiting here for the same + * pthread to exit. + */ + + (void)pthread_takesemaphore(&pjoin->exit_sem); + + /* The thread has exited! Get the thread exit value */ + + if (pexit_value) + { + *pexit_value = pjoin->exit_value; + sdbg("exit_value=0x%p\n", pjoin->exit_value); + } + + /* Post the thread's data semaphore so that the exitting thread + * will know that we have received the data. + */ + + (void)pthread_givesemaphore(&pjoin->data_sem); + + /* Retake the join semaphore, we need to hold this when + * pthread_destroyjoin is called. + */ + + (void)pthread_takesemaphore(&g_join_semaphore); + } + + /* Pre-emption is okay now. The logic still cannot be re-entered + * because we hold the join semaphore + */ + + sched_unlock(); + + /* Release our reference to the join structure and, if the reference + * count decrements to zero, deallocate the join structure. + */ + + if (--pjoin->crefs <= 0) + { + (void)pthread_destroyjoin(pjoin); + } + + (void)pthread_givesemaphore(&g_join_semaphore); + ret = OK; + } + + sdbg("Returning %d\n", ret); + return ret; +} + |