xref: /dflybsd-src/lib/libthread_xu/thread/thr_spinlock.c (revision 940be950819fa932cd401a01f1182bf686a2e61e)

/*
 * Copyright (c) 1997 John Birrell <jb@cimlogic.com.au>.
 * All rights reserved.
 *
 * 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 of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL 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 AUTHOR 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.
 *
 */

#include <sys/types.h>
#include <machine/atomic.h>
#include <machine/tls.h>
#include <pthread.h>
#include <libc_private.h>
#include "spinlock.h"

#include "thr_private.h"

#define	MAX_SPINLOCKS	256

/*
 * These data structures are used to trace all spinlocks
 * in libc.
 */
struct spinlock_extra {
	spinlock_t	*owner;
};

static umtx_t			spinlock_static_lock;
static struct spinlock_extra	extra[MAX_SPINLOCKS];
static int			spinlock_count;
static int			initialized;

static void	init_spinlock(spinlock_t *lck);

/*
 * These functions implement temporary spinlocks as used by libc.
 * these are not persistent spinlocks, so we use the API for
 * temporary locks which block all signals for the duration.
 */
void
_spinunlock(spinlock_t *lck)
{
	pthread_t curthread = tls_get_curthread();

	THR_UMTX_UNLOCK(curthread, (volatile umtx_t *)&lck->access_lock);
}

void
_spinlock(spinlock_t *lck)
{
	pthread_t curthread;

	if (!__isthreaded)
		PANIC("Spinlock called when not threaded.");
	if (!initialized)
		PANIC("Spinlocks not initialized.");
	if (lck->fname == NULL)
		init_spinlock(lck);

	curthread = tls_get_curthread();
	THR_UMTX_LOCK(curthread, (volatile umtx_t *)&lck->access_lock);
}

/*
 * Returns 0 on success, else EBUSY
 */
int
_spintrylock(spinlock_t *lck)
{
	pthread_t curthread;

	if (!__isthreaded)
		PANIC("Spinlock called when not threaded.");
	if (!initialized)
		PANIC("Spinlocks not initialized.");
	if (lck->fname == NULL)
		init_spinlock(lck);

	curthread = tls_get_curthread();
	return(THR_UMTX_TRYLOCK(curthread,
				(volatile umtx_t *)&lck->access_lock));
}

void
_spinlock_debug(spinlock_t *lck, char *fname __unused, int lineno __unused)
{
	_spinlock(lck);
}

static void
init_spinlock(spinlock_t *lck)
{
	static int count = 0;
	pthread_t curthread = tls_get_curthread();

	THR_UMTX_LOCK(curthread, &spinlock_static_lock);
	if ((lck->fname == NULL) && (spinlock_count < MAX_SPINLOCKS)) {
		lck->fname = (char *)&extra[spinlock_count];
		extra[spinlock_count].owner = lck;
		spinlock_count++;
	}
	THR_UMTX_UNLOCK(curthread, &spinlock_static_lock);
	if (lck->fname == NULL && ++count < 5)
		stderr_debug("Warning: exceeded max spinlocks");
}

void
_thr_spinlock_init(void)
{
	int i;

	_thr_umtx_init(&spinlock_static_lock);
	if (initialized != 0) {
		/*
		 * called after fork() to reset state of libc spin locks,
		 * it is not quite right since libc may be in inconsistent
		 * state, resetting the locks to allow current thread to be
		 * able to hold them may not help things too much, but
		 * anyway, we do our best.
		 * it is better to do pthread_atfork in libc.
		 */
		for (i = 0; i < spinlock_count; i++)
			_thr_umtx_init((volatile umtx_t *)
				&extra[i].owner->access_lock);
	} else {
		initialized = 1;
	}
}