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1 jermar 1 
/*
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 * Copyright (c) 2001-2004 Jakub Jermar
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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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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - 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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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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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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/** @addtogroup sync
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 * @{
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 */
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/**
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 * @file
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 * @brief   Spinlocks.
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 */
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#include <synch/spinlock.h>
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#include <atomic.h>
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#include <arch/barrier.h>
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#include <arch.h>
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#include <preemption.h>
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#include <print.h>
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#include <debug.h>
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#include <symtab.h>
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#ifdef CONFIG_FB
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#include <genarch/fb/fb.h>
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#endif
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#ifdef CONFIG_SMP
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/** Initialize spinlock
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 *
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 * Initialize spinlock.
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 *
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 * @param sl Pointer to spinlock_t structure.
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 */
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void spinlock_initialize(spinlock_t *sl, char *name)
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{
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    atomic_set(&sl->val, 0);
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#ifdef CONFIG_DEBUG_SPINLOCK
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    sl->name = name;
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#endif 
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}
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/** Lock spinlock
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 *
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 * Lock spinlock.
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 * This version has limitted ability to report
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 * possible occurence of deadlock.
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 *
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 * @param sl Pointer to spinlock_t structure.
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 */
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#ifdef CONFIG_DEBUG_SPINLOCK
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void spinlock_lock_debug(spinlock_t *sl)
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{
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    count_t i = 0;
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    char *symbol;
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    bool deadlock_reported = false;
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    preemption_disable();
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    while (test_and_set(&sl->val)) {
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        /*
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         * We need to be careful about printf_lock and fb_lock.
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         * Both of them are used to report deadlocks via
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         * printf() and fb_putchar().
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         *
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         * We trust our code that there is no possible deadlock
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         * caused by these two locks (except when an exception
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         * is triggered for instance by printf() or fb_putchar()).
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         * However, we encountered false positives caused by very
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         * slow VESA framebuffer interaction (especially when
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         * run in a simulator) that caused problems with both
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         * printf_lock and fb_lock.
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         *
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         * Possible deadlocks on both printf_lock and fb_lock
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         * are therefore not reported as they would cause an
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         * infinite recursion.
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         */
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        if (sl == &printf_lock)
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            continue;
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#ifdef CONFIG_FB
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        if (sl == &fb_lock)
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            continue;
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#endif
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        if (i++ > DEADLOCK_THRESHOLD) {
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            printf("cpu%u: looping on spinlock %" PRIp ":%s, caller=%" PRIp,
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                CPU->id, sl, sl->name, CALLER);
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            symbol = get_symtab_entry(CALLER);
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            if (symbol)
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                printf("(%s)", symbol);
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            printf("\n");
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            i = 0;
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            deadlock_reported = true;
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        }
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    }
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    if (deadlock_reported)
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        printf("cpu%u: not deadlocked\n", CPU->id);
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    /*
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     * Prevent critical section code from bleeding out this way up.
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     */
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    CS_ENTER_BARRIER();
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}
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#endif
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/** Lock spinlock conditionally
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 *
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 * Lock spinlock conditionally.
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 * If the spinlock is not available at the moment,
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 * signal failure.
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 *
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 * @param sl Pointer to spinlock_t structure.
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 *
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 * @return Zero on failure, non-zero otherwise.
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 */
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int spinlock_trylock(spinlock_t *sl)
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{
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    int rc;
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    preemption_disable();
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    rc = !test_and_set(&sl->val);
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    /*
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     * Prevent critical section code from bleeding out this way up.
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     */
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    CS_ENTER_BARRIER();
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    if (!rc)
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        preemption_enable();
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    return rc;
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}
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#endif
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/** @}
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 */