Subversion Repositories HelenOS

Rev

Rev 4247 | Details | Compare with Previous | Last modification | View Log | RSS feed

Rev Author Line No. Line
1 jermar 1 
/*
2071 jermar 2 
 * Copyright (c) 2001-2004 Jakub Jermar
1 jermar 3 
 * All rights reserved.
4 
 *
5 
 * Redistribution and use in source and binary forms, with or without
6 
 * modification, are permitted provided that the following conditions
7 
 * are met:
8 
 *
9 
 * - Redistributions of source code must retain the above copyright
10 
 *   notice, this list of conditions and the following disclaimer.
11 
 * - Redistributions in binary form must reproduce the above copyright
12 
 *   notice, this list of conditions and the following disclaimer in the
13 
 *   documentation and/or other materials provided with the distribution.
14 
 * - The name of the author may not be used to endorse or promote products
15 
 *   derived from this software without specific prior written permission.
16 
 *
17 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 
 */
28 
 
1757 jermar 29 
/** @addtogroup sync
1702 cejka 30 
 * @{
31 
 */
32 
 
1264 jermar 33 
/**
1702 cejka 34 
 * @file
4220 decky 35 
 * @brief Spinlocks.
1264 jermar 36 
 */
4220 decky 37 
 
383 jermar 38 
#include <synch/spinlock.h>
1104 jermar 39 
#include <atomic.h>
153 jermar 40 
#include <arch/barrier.h>
383 jermar 41 
#include <arch.h>
223 jermar 42 
#include <preemption.h>
195 vana 43 
#include <print.h>
383 jermar 44 
#include <debug.h>
552 palkovsky 45 
#include <symtab.h>
1 jermar 46 
 
1313 jermar 47 
#ifdef CONFIG_FB
48 
#include <genarch/fb/fb.h>
49 
#endif
50 
 
458 decky 51 
#ifdef CONFIG_SMP
1 jermar 52 
 
383 jermar 53 
/** Initialize spinlock
54 
 *
55 
 * Initialize spinlock.
56 
 *
57 
 * @param sl Pointer to spinlock_t structure.
58 
 */
552 palkovsky 59 
void spinlock_initialize(spinlock_t *sl, char *name)
1 jermar 60 
{
625 palkovsky 61 
    atomic_set(&sl->val, 0);
552 palkovsky 62 
#ifdef CONFIG_DEBUG_SPINLOCK
63 
    sl->name = name;
64 
#endif 
1 jermar 65 
}
66 
 
383 jermar 67 
/** Lock spinlock
68 
 *
69 
 * Lock spinlock.
70 
 * This version has limitted ability to report
71 
 * possible occurence of deadlock.
72 
 *
73 
 * @param sl Pointer to spinlock_t structure.
74 
 */
1100 palkovsky 75 
#ifdef CONFIG_DEBUG_SPINLOCK
76 
void spinlock_lock_debug(spinlock_t *sl)
1 jermar 77 
{
4490 decky 78 
    size_t i = 0;
4132 svoboda 79 
    bool deadlock_reported = false;
1 jermar 80 
 
223 jermar 81 
    preemption_disable();
1 jermar 82 
    while (test_and_set(&sl->val)) {
1313 jermar 83 
 
84 
        /*
2211 decky 85 
         * We need to be careful about printf_lock and fb_lock.
1313 jermar 86 
         * Both of them are used to report deadlocks via
87 
         * printf() and fb_putchar().
88 
         *
89 
         * We trust our code that there is no possible deadlock
90 
         * caused by these two locks (except when an exception
91 
         * is triggered for instance by printf() or fb_putchar()).
92 
         * However, we encountered false positives caused by very
93 
         * slow VESA framebuffer interaction (especially when
94 
         * run in a simulator) that caused problems with both
2211 decky 95 
         * printf_lock and fb_lock.
1313 jermar 96 
         *
2211 decky 97 
         * Possible deadlocks on both printf_lock and fb_lock
1313 jermar 98 
         * are therefore not reported as they would cause an
99 
         * infinite recursion.
100 
         */
2211 decky 101 
        if (sl == &printf_lock)
1313 jermar 102 
            continue;
103 
#ifdef CONFIG_FB
104 
        if (sl == &fb_lock)
105 
            continue;
106 
#endif
1667 jermar 107 
        if (i++ > DEADLOCK_THRESHOLD) {
4137 svoboda 108 
            printf("cpu%u: looping on spinlock %" PRIp ":%s, "
4247 decky 109 
                "caller=%" PRIp "(%s)\n", CPU->id, sl, sl->name,
4137 svoboda 110 
                CALLER, symtab_fmt_name_lookup(CALLER));
4247 decky 111 
 
1 jermar 112 
            i = 0;
557 jermar 113 
            deadlock_reported = true;
1 jermar 114 
        }
115 
    }
383 jermar 116 
 
557 jermar 117 
    if (deadlock_reported)
3059 decky 118 
        printf("cpu%u: not deadlocked\n", CPU->id);
557 jermar 119 
 
383 jermar 120 
    /*
121 
     * Prevent critical section code from bleeding out this way up.
122 
     */
153 jermar 123 
    CS_ENTER_BARRIER();
1 jermar 124 
}
125 
#endif
126 
 
383 jermar 127 
/** Lock spinlock conditionally
128 
 *
129 
 * Lock spinlock conditionally.
130 
 * If the spinlock is not available at the moment,
131 
 * signal failure.
132 
 *
133 
 * @param sl Pointer to spinlock_t structure.
134 
 *
135 
 * @return Zero on failure, non-zero otherwise.
136 
 */
1 jermar 137 
int spinlock_trylock(spinlock_t *sl)
138 
{
153 jermar 139 
    int rc;
140 
 
223 jermar 141 
    preemption_disable();
153 jermar 142 
    rc = !test_and_set(&sl->val);
383 jermar 143 
 
144 
    /*
145 
     * Prevent critical section code from bleeding out this way up.
146 
     */
153 jermar 147 
    CS_ENTER_BARRIER();
223 jermar 148 
 
149 
    if (!rc)
150 
        preemption_enable();
153 jermar 151 
 
152 
    return rc;
1 jermar 153 
}
154 
 
155 
#endif
1702 cejka 156 
 
1757 jermar 157 
/** @}
1702 cejka 158 
 */