/*      $OpenBSD: mutex.c,v 1.17 2019/04/23 13:35:12 visa Exp $ */

/*
 * Copyright (c) 2004 Artur Grabowski <art@openbsd.org>
 * 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. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission. 
 *
 * THIS SOFTWARE IS PROVIDED ``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 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/param.h>
#include <sys/mutex.h>
#include <sys/systm.h>
#include <sys/atomic.h>

#include <machine/intr.h>

#include <ddb/db_output.h>

#ifdef MULTIPROCESSOR
/* Note: lock must be 16-byte aligned. */
#define __mtx_lock(mtx) ((int *)(((vaddr_t)mtx->mtx_lock + 0xf) & ~0xf))
#endif

void
__mtx_init(struct mutex *mtx, int wantipl)
{
#ifdef MULTIPROCESSOR
        mtx->mtx_lock[0] = 1;
        mtx->mtx_lock[1] = 1;
        mtx->mtx_lock[2] = 1;
        mtx->mtx_lock[3] = 1;
#endif
        mtx->mtx_wantipl = wantipl;
        mtx->mtx_oldipl = IPL_NONE;
        mtx->mtx_owner = NULL;
}

#ifdef MULTIPROCESSOR
void
mtx_enter(struct mutex *mtx)
{
        while (mtx_enter_try(mtx) == 0)
                ;
}

int
mtx_enter_try(struct mutex *mtx)
{
        struct cpu_info *ci = curcpu();
        volatile int *lock = __mtx_lock(mtx);
        int ret;
        int s;

        if (mtx->mtx_wantipl != IPL_NONE)
                s = splraise(mtx->mtx_wantipl);

#ifdef DIAGNOSTIC
        if (__predict_false(mtx->mtx_owner == ci))
                panic("mtx %p: locking against myself", mtx);
#endif

        asm volatile (
                "ldcws      0(%2), %0"
                : "=&r" (ret), "+m" (lock)
                : "r" (lock)
        );

        if (ret) {
                membar_enter();
                mtx->mtx_owner = ci;
                if (mtx->mtx_wantipl != IPL_NONE)
                        mtx->mtx_oldipl = s;
#ifdef DIAGNOSTIC
                ci->ci_mutex_level++;
#endif

                return (1);
        }

        if (mtx->mtx_wantipl != IPL_NONE)
                splx(s);

        return (0);
}
#else
void
mtx_enter(struct mutex *mtx)
{
        struct cpu_info *ci = curcpu();

#ifdef DIAGNOSTIC
        if (__predict_false(mtx->mtx_owner == ci))
                panic("mtx %p: locking against myself", mtx);
#endif

        if (mtx->mtx_wantipl != IPL_NONE)
                mtx->mtx_oldipl = splraise(mtx->mtx_wantipl);

        mtx->mtx_owner = ci;

#ifdef DIAGNOSTIC
        ci->ci_mutex_level++;
#endif
}

int
mtx_enter_try(struct mutex *mtx)
{
        mtx_enter(mtx);
        return (1);
}
#endif

void
mtx_leave(struct mutex *mtx)
{
#ifdef MULTIPROCESSOR
        volatile int *lock = __mtx_lock(mtx);
#endif
        int s;

        MUTEX_ASSERT_LOCKED(mtx);

#ifdef DIAGNOSTIC
        curcpu()->ci_mutex_level--;
#endif
        s = mtx->mtx_oldipl;
        mtx->mtx_owner = NULL;
#ifdef MULTIPROCESSOR
        membar_exit();
        *lock = 1;
#endif

        if (mtx->mtx_wantipl != IPL_NONE)
                splx(s);
}