| /**************************************************************************** |
| * pthread_join.c |
| * |
| * Copyright (C) 2007, 2008, 2011, 2013 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 "group_internal.h" |
| #include "pthread_internal.h" |
| |
| /**************************************************************************** |
| * Pre-processor 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. |
| * |
| * The caller's task/thread must belong to the same "task group" as the |
| * pthread is (or was) a member of. The thread may or may not still |
| * be running. |
| * |
| * 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 joinable |
| * thread. |
| * ESRCH No thread could be found corresponding to that specified 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 struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head; |
| FAR struct task_group_s *group = rtcb->group; |
| FAR struct join_s *pjoin; |
| int ret; |
| |
| sdbg("thread=%d group=%p\n", thread, group); |
| DEBUGASSERT(group); |
| |
| /* 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(&group->tg_joinsem); |
| |
| /* 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 exited. |
| */ |
| |
| pjoin = pthread_findjoininfo(group, (pid_t)thread); |
| if (!pjoin) |
| { |
| /* Determine what kind of error to return */ |
| |
| FAR struct tcb_s *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(&group->tg_joinsem); |
| } |
| 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(&group->tg_joinsem); |
| |
| /* 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 exiting 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(&group->tg_joinsem); |
| } |
| |
| /* 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(group, pjoin); |
| } |
| |
| (void)pthread_givesemaphore(&group->tg_joinsem); |
| ret = OK; |
| } |
| |
| sdbg("Returning %d\n", ret); |
| return ret; |
| } |
