aad93b043a
used a global pthread_mutex_t for synchronization. r179417 replaced that with an implementation that directly used atomic instructions and thr_* syscalls to synchronize callers to pthread_once. However, calling pthread_mutex_lock on the global mutex implicitly ensured that _thr_check_init() had been called but with r179417 this was no longer guaranteed. This meant that if you were unlucky enough to have your first call into libthr be a call to pthread_once(), you would segfault when trying to access the pointer returned by _get_curthread(). The fix is to explicitly call _thr_check_init() from pthread_once(). Reviewed by: davidxu Approved by: emaste (mentor) MFC after: 1 week
100 lines
3.1 KiB
C
100 lines
3.1 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 <pthread.h>
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#include "un-namespace.h"
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#include "thr_private.h"
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__weak_reference(_pthread_once, pthread_once);
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#define ONCE_NEVER_DONE PTHREAD_NEEDS_INIT
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#define ONCE_DONE PTHREAD_DONE_INIT
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#define ONCE_IN_PROGRESS 0x02
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#define ONCE_WAIT 0x03
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/*
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* POSIX:
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* The pthread_once() function is not a cancellation point. However,
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* if init_routine is a cancellation point and is canceled, the effect
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* on once_control shall be as if pthread_once() was never called.
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*/
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static void
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once_cancel_handler(void *arg)
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{
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pthread_once_t *once_control = arg;
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if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_NEVER_DONE))
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return;
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atomic_store_rel_int(&once_control->state, ONCE_NEVER_DONE);
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_thr_umtx_wake(&once_control->state, INT_MAX, 0);
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}
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int
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_pthread_once(pthread_once_t *once_control, void (*init_routine) (void))
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{
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struct pthread *curthread;
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int state;
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_thr_check_init();
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for (;;) {
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state = once_control->state;
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if (state == ONCE_DONE)
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return (0);
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if (state == ONCE_NEVER_DONE) {
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if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_IN_PROGRESS))
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break;
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} else if (state == ONCE_IN_PROGRESS) {
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if (atomic_cmpset_acq_int(&once_control->state, state, ONCE_WAIT))
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_thr_umtx_wait_uint(&once_control->state, ONCE_WAIT, NULL, 0);
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} else if (state == ONCE_WAIT) {
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_thr_umtx_wait_uint(&once_control->state, state, NULL, 0);
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} else
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return (EINVAL);
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}
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curthread = _get_curthread();
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THR_CLEANUP_PUSH(curthread, once_cancel_handler, once_control);
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init_routine();
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THR_CLEANUP_POP(curthread, 0);
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if (atomic_cmpset_rel_int(&once_control->state, ONCE_IN_PROGRESS, ONCE_DONE))
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return (0);
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atomic_store_rel_int(&once_control->state, ONCE_DONE);
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_thr_umtx_wake(&once_control->state, INT_MAX, 0);
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return (0);
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}
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void
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_thr_once_init()
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{
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}
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