source: mainline/generic/src/synch/spinlock.c@ 169c408

/*
 * Copyright (C) 2001-2004 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - 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 BY THE AUTHOR ``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 <synch/spinlock.h>
#include <arch/atomic.h>
#include <arch/barrier.h>
#include <arch.h>
#include <preemption.h>
#include <print.h>
#include <debug.h>

#ifdef __SMP__

/** Initialize spinlock
 *
 * Initialize spinlock.
 *
 * @param sl Pointer to spinlock_t structure.
 */
void spinlock_initialize(spinlock_t *sl)
{
        sl->val = 0;
}

#ifdef DEBUG_SPINLOCK
/** Lock spinlock
 *
 * Lock spinlock.
 * This version has limitted ability to report 
 * possible occurence of deadlock.
 *
 * @param sl Pointer to spinlock_t structure.
 */
void spinlock_lock(spinlock_t *sl)
{
        int i = 0;
        __address caller = ((__u32 *) &sl)[-1];

        preemption_disable();
        while (test_and_set(&sl->val)) {
                if (i++ > 300000) {
                        printf("cpu%d: looping on spinlock %X, caller=%X\n", CPU->id, sl, caller);
                        i = 0;
                }
        }

        /*
         * Prevent critical section code from bleeding out this way up.
         */
        CS_ENTER_BARRIER();

}

#else

/** Lock spinlock
 *
 * Lock spinlock.
 *
 * @param sl Pointer to spinlock_t structure.
 */
void spinlock_lock(spinlock_t *sl)
{
        preemption_disable();

        /*
         * Each architecture has its own efficient/recommended
         * implementation of spinlock.
         */
        spinlock_arch(&sl->val);

        /*
         * Prevent critical section code from bleeding out this way up.
         */
        CS_ENTER_BARRIER();
}
#endif

/** Lock spinlock conditionally
 *
 * Lock spinlock conditionally.
 * If the spinlock is not available at the moment,
 * signal failure.
 *
 * @param sl Pointer to spinlock_t structure.
 *
 * @return Zero on failure, non-zero otherwise.
 */
int spinlock_trylock(spinlock_t *sl)
{
        int rc;
        
        preemption_disable();
        rc = !test_and_set(&sl->val);

        /*
         * Prevent critical section code from bleeding out this way up.
         */
        CS_ENTER_BARRIER();

        if (!rc)
                preemption_enable();
        
        return rc;
}

/** Unlock spinlock
 *
 * Unlock spinlock.
 *
 * @param sl Pointer to spinlock_t structure.
 */
void spinlock_unlock(spinlock_t *sl)
{
        ASSERT(sl->val != 0);

        /*
         * Prevent critical section code from bleeding out this way down.
         */
        CS_LEAVE_BARRIER();
        
        sl->val = 0;
        preemption_enable();
}

#endif