| 1 | /*
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| 2 | * Copyright (C) 2001-2004 Jakub Jermar
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| 3 | * All rights reserved.
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| 4 | *
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| 5 | * Redistribution and use in source and binary forms, with or without
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| 6 | * modification, are permitted provided that the following conditions
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| 7 | * are met:
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| 8 | *
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| 9 | * - Redistributions of source code must retain the above copyright
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| 10 | * notice, this list of conditions and the following disclaimer.
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| 11 | * - Redistributions in binary form must reproduce the above copyright
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| 12 | * notice, this list of conditions and the following disclaimer in the
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| 13 | * documentation and/or other materials provided with the distribution.
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| 14 | * - The name of the author may not be used to endorse or promote products
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| 15 | * derived from this software without specific prior written permission.
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| 16 | *
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| 17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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| 18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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| 19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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| 20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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| 21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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| 22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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| 23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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| 24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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| 26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 27 | */
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| 28 |
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| 29 | /** @addtogroup sync
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| 30 | * @{
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| 31 | */
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| 32 |
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| 33 | /**
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| 34 | * @file
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| 35 | * @brief Spinlocks.
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| 36 | */
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| 37 |
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| 38 | #include <synch/spinlock.h>
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| 39 | #include <atomic.h>
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| 40 | #include <arch/barrier.h>
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| 41 | #include <arch.h>
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| 42 | #include <preemption.h>
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| 43 | #include <print.h>
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| 44 | #include <debug.h>
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| 45 | #include <symtab.h>
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| 46 |
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| 47 | #ifdef CONFIG_FB
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| 48 | #include <genarch/fb/fb.h>
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| 49 | #endif
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| 50 |
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| 51 | #ifdef CONFIG_SMP
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| 52 |
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| 53 | /** Initialize spinlock
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| 54 | *
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| 55 | * Initialize spinlock.
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| 56 | *
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| 57 | * @param sl Pointer to spinlock_t structure.
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| 58 | */
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| 59 | void spinlock_initialize(spinlock_t *sl, char *name)
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| 60 | {
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| 61 | atomic_set(&sl->val, 0);
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| 62 | #ifdef CONFIG_DEBUG_SPINLOCK
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| 63 | sl->name = name;
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| 64 | #endif
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| 65 | }
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| 66 |
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| 67 | /** Lock spinlock
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| 68 | *
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| 69 | * Lock spinlock.
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| 70 | * This version has limitted ability to report
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| 71 | * possible occurence of deadlock.
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| 72 | *
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| 73 | * @param sl Pointer to spinlock_t structure.
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| 74 | */
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| 75 | #ifdef CONFIG_DEBUG_SPINLOCK
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| 76 | #define DEADLOCK_THRESHOLD 100000000
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| 77 | void spinlock_lock_debug(spinlock_t *sl)
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| 78 | {
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| 79 | count_t i = 0;
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| 80 | char *symbol;
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| 81 | bool deadlock_reported = false;
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| 82 |
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| 83 | preemption_disable();
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| 84 | while (test_and_set(&sl->val)) {
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| 85 |
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| 86 | /*
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| 87 | * We need to be careful about printflock and fb_lock.
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| 88 | * Both of them are used to report deadlocks via
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| 89 | * printf() and fb_putchar().
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| 90 | *
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| 91 | * We trust our code that there is no possible deadlock
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| 92 | * caused by these two locks (except when an exception
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| 93 | * is triggered for instance by printf() or fb_putchar()).
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| 94 | * However, we encountered false positives caused by very
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| 95 | * slow VESA framebuffer interaction (especially when
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| 96 | * run in a simulator) that caused problems with both
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| 97 | * printflock and fb_lock.
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| 98 | *
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| 99 | * Possible deadlocks on both printflock and fb_lock
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| 100 | * are therefore not reported as they would cause an
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| 101 | * infinite recursion.
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| 102 | */
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| 103 | if (sl == &printflock)
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| 104 | continue;
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| 105 | #ifdef CONFIG_FB
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| 106 | if (sl == &fb_lock)
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| 107 | continue;
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| 108 | #endif
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| 109 | if (i++ > DEADLOCK_THRESHOLD) {
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| 110 | printf("cpu%d: looping on spinlock %.*p:%s, caller=%.*p",
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| 111 | CPU->id, sizeof(uintptr_t) * 2, sl, sl->name, sizeof(uintptr_t) * 2, CALLER);
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| 112 | symbol = get_symtab_entry(CALLER);
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| 113 | if (symbol)
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| 114 | printf("(%s)", symbol);
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| 115 | printf("\n");
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| 116 | i = 0;
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| 117 | deadlock_reported = true;
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| 118 | }
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| 119 | }
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| 120 |
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| 121 | if (deadlock_reported)
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| 122 | printf("cpu%d: not deadlocked\n", CPU->id);
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| 123 |
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| 124 | /*
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| 125 | * Prevent critical section code from bleeding out this way up.
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| 126 | */
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| 127 | CS_ENTER_BARRIER();
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| 128 | }
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| 129 | #endif
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| 130 |
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| 131 | /** Lock spinlock conditionally
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| 132 | *
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| 133 | * Lock spinlock conditionally.
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| 134 | * If the spinlock is not available at the moment,
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| 135 | * signal failure.
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| 136 | *
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| 137 | * @param sl Pointer to spinlock_t structure.
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| 138 | *
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| 139 | * @return Zero on failure, non-zero otherwise.
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| 140 | */
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| 141 | int spinlock_trylock(spinlock_t *sl)
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| 142 | {
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| 143 | int rc;
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| 144 |
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| 145 | preemption_disable();
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| 146 | rc = !test_and_set(&sl->val);
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| 147 |
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| 148 | /*
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| 149 | * Prevent critical section code from bleeding out this way up.
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| 150 | */
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| 151 | CS_ENTER_BARRIER();
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| 152 |
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| 153 | if (!rc)
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| 154 | preemption_enable();
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| 155 |
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| 156 | return rc;
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| 157 | }
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| 158 |
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| 159 | #endif
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| 160 |
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| 161 | /** @}
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| 162 | */
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