635f917a9d
which does not know what is the state of interrupted system call, for example, open() system call opened a file and the thread is still cancelled, result is descriptor leak, there are other problems which can cause resource leak or undeterminable side effect when a thread is cancelled. However, this is no longer true in new implementation. In defering mode, a thread is canceled if cancellation request is pending and later the thread enters a cancellation point, otherwise, a later pthread_cancel() just causes SIGCANCEL to be sent to the target thread, and causes target thread to abort system call, userland code in libthr then checks cancellation state, and cancels the thread if needed. For example, the cancellation point open(), the thread may be canceled at start, but later, if it opened a file descriptor, it is not canceled, this avoids file handle leak. Another example is read(), a thread may be canceled at start of the function, but later, if it read some bytes from a socket, the thread is not canceled, the caller then can decide if it should still enable cancelling or disable it and continue reading data until it thinks it has read all bytes of a packet, and keeps a protocol stream in health state, if user ignores partly reading of a packet without disabling cancellation, then second iteration of read loop cause the thread to be cancelled. An exception is that the close() cancellation point always closes a file handle despite whether the thread is cancelled or not. The old mechanism is still kept, for a functions which is not so easily to fix a cancellation problem, the rough mechanism is used. Reviewed by: kib@
151 lines
4.1 KiB
C
151 lines
4.1 KiB
C
/*
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* Copyright (c) 2005, David Xu <davidxu@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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*/
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#include "namespace.h"
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#include <errno.h>
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#include <pthread.h>
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#include "un-namespace.h"
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#include "thr_private.h"
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int _pthread_timedjoin_np(pthread_t pthread, void **thread_return,
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const struct timespec *abstime);
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static int join_common(pthread_t, void **, const struct timespec *);
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__weak_reference(_pthread_join, pthread_join);
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__weak_reference(_pthread_timedjoin_np, pthread_timedjoin_np);
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static void backout_join(void *arg)
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{
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struct pthread *curthread = _get_curthread();
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struct pthread *pthread = (struct pthread *)arg;
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THREAD_LIST_LOCK(curthread);
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pthread->joiner = NULL;
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THREAD_LIST_UNLOCK(curthread);
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}
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int
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_pthread_join(pthread_t pthread, void **thread_return)
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{
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return (join_common(pthread, thread_return, NULL));
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}
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int
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_pthread_timedjoin_np(pthread_t pthread, void **thread_return,
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const struct timespec *abstime)
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{
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if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
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abstime->tv_nsec >= 1000000000)
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return (EINVAL);
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return (join_common(pthread, thread_return, abstime));
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}
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/*
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* Cancellation behavior:
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* if the thread is canceled, joinee is not recycled.
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*/
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static int
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join_common(pthread_t pthread, void **thread_return,
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const struct timespec *abstime)
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{
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struct pthread *curthread = _get_curthread();
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struct timespec ts, ts2, *tsp;
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void *tmp;
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long tid;
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int ret = 0;
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if (pthread == NULL)
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return (EINVAL);
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if (pthread == curthread)
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return (EDEADLK);
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THREAD_LIST_LOCK(curthread);
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if ((ret = _thr_find_thread(curthread, pthread, 1)) != 0) {
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ret = ESRCH;
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} else if ((pthread->tlflags & TLFLAGS_DETACHED) != 0) {
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ret = EINVAL;
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} else if (pthread->joiner != NULL) {
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/* Multiple joiners are not supported. */
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ret = ENOTSUP;
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}
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if (ret) {
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THREAD_LIST_UNLOCK(curthread);
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return (ret);
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}
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/* Set the running thread to be the joiner: */
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pthread->joiner = curthread;
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THREAD_LIST_UNLOCK(curthread);
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THR_CLEANUP_PUSH(curthread, backout_join, pthread);
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_thr_cancel_enter_defer(curthread, 1);
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tid = pthread->tid;
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while (pthread->tid != TID_TERMINATED) {
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_thr_testcancel(curthread);
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if (abstime != NULL) {
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clock_gettime(CLOCK_REALTIME, &ts);
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TIMESPEC_SUB(&ts2, abstime, &ts);
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if (ts2.tv_sec < 0) {
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ret = ETIMEDOUT;
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break;
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}
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tsp = &ts2;
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} else
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tsp = NULL;
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ret = _thr_umtx_wait(&pthread->tid, tid, tsp);
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if (ret == ETIMEDOUT)
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break;
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}
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_thr_cancel_leave_defer(curthread, 0);
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THR_CLEANUP_POP(curthread, 0);
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if (ret == ETIMEDOUT) {
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THREAD_LIST_LOCK(curthread);
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pthread->joiner = NULL;
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THREAD_LIST_UNLOCK(curthread);
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} else {
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ret = 0;
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tmp = pthread->ret;
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THREAD_LIST_LOCK(curthread);
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pthread->tlflags |= TLFLAGS_DETACHED;
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pthread->joiner = NULL;
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THR_GCLIST_ADD(pthread);
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THREAD_LIST_UNLOCK(curthread);
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if (thread_return != NULL)
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*thread_return = tmp;
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}
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return (ret);
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}
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