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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 | /* * Copyright (c) 2016 Wind River Systems, Inc. * * SPDX-License-Identifier: Apache-2.0 */ /** * @file @brief mutex kernel services * * This module contains routines for handling mutex locking and unlocking. * * Mutexes implement a priority inheritance algorithm that boosts the priority * level of the owning thread to match the priority level of the highest * priority thread waiting on the mutex. * * Each mutex that contributes to priority inheritance must be released in the * reverse order in which is was acquired. Furthermore each subsequent mutex * that contributes to raising the owning thread's priority level must be * acquired at a point after the most recent "bumping" of the priority level. * * For example, if thread A has two mutexes contributing to the raising of its * priority level, the second mutex M2 must be acquired by thread A after * thread A's priority level was bumped due to owning the first mutex M1. * When releasing the mutex, thread A must release M2 before it releases M1. * Failure to follow this nested model may result in threads running at * unexpected priority levels (too high, or too low). */ #include <kernel.h> #include <kernel_structs.h> #include <toolchain.h> #include <linker/sections.h> #include <wait_q.h> #include <misc/dlist.h> #include <debug/object_tracing_common.h> #include <errno.h> #include <init.h> #define RECORD_STATE_CHANGE(mutex) do { } while ((0)) #define RECORD_CONFLICT(mutex) do { } while ((0)) extern struct k_mutex _k_mutex_list_start[]; extern struct k_mutex _k_mutex_list_end[]; #ifdef CONFIG_OBJECT_TRACING struct k_mutex *_trace_list_k_mutex; /* * Complete initialization of statically defined mutexes. */ static int init_mutex_module(struct device *dev) { ARG_UNUSED(dev); struct k_mutex *mutex; for (mutex = _k_mutex_list_start; mutex < _k_mutex_list_end; mutex++) { SYS_TRACING_OBJ_INIT(k_mutex, mutex); } return 0; } SYS_INIT(init_mutex_module, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_OBJECTS); #endif /* CONFIG_OBJECT_TRACING */ void k_mutex_init(struct k_mutex *mutex) { mutex->owner = NULL; mutex->lock_count = 0; /* initialized upon first use */ /* mutex->owner_orig_prio = 0; */ sys_dlist_init(&mutex->wait_q); SYS_TRACING_OBJ_INIT(k_mutex, mutex); } static int new_prio_for_inheritance(int target, int limit) { int new_prio = _is_prio_higher(target, limit) ? target : limit; new_prio = _get_new_prio_with_ceiling(new_prio); return new_prio; } static void adjust_owner_prio(struct k_mutex *mutex, int new_prio) { if (mutex->owner->base.prio != new_prio) { K_DEBUG("%p (ready (y/n): %c) prio changed to %d (was %d)\n", mutex->owner, _is_thread_ready(mutex->owner) ? 'y' : 'n', new_prio, mutex->owner->base.prio); _thread_priority_set(mutex->owner, new_prio); } } int k_mutex_lock(struct k_mutex *mutex, s32_t timeout) { int new_prio, key; _sched_lock(); if (likely(mutex->lock_count == 0 || mutex->owner == _current)) { RECORD_STATE_CHANGE(); mutex->owner_orig_prio = mutex->lock_count == 0 ? _current->base.prio : mutex->owner_orig_prio; mutex->lock_count++; mutex->owner = _current; K_DEBUG("%p took mutex %p, count: %d, orig prio: %d\n", _current, mutex, mutex->lock_count, mutex->owner_orig_prio); k_sched_unlock(); return 0; } RECORD_CONFLICT(); if (unlikely(timeout == K_NO_WAIT)) { k_sched_unlock(); return -EBUSY; } #if 0 if (_is_prio_higher(_current->prio, mutex->owner->prio)) { new_prio = _current->prio; } new_prio = _get_new_prio_with_ceiling(new_prio); #endif new_prio = new_prio_for_inheritance(_current->base.prio, mutex->owner->base.prio); key = irq_lock(); K_DEBUG("adjusting prio up on mutex %p\n", mutex); if (_is_prio_higher(new_prio, mutex->owner->base.prio)) { adjust_owner_prio(mutex, new_prio); } _pend_current_thread(&mutex->wait_q, timeout); int got_mutex = _Swap(key); K_DEBUG("on mutex %p got_mutex value: %d\n", mutex, got_mutex); K_DEBUG("%p got mutex %p (y/n): %c\n", _current, mutex, got_mutex ? 'y' : 'n'); if (got_mutex == 0) { k_sched_unlock(); return 0; } /* timed out */ K_DEBUG("%p timeout on mutex %p\n", _current, mutex); struct k_thread *waiter = (struct k_thread *)sys_dlist_peek_head(&mutex->wait_q); new_prio = mutex->owner_orig_prio; new_prio = waiter ? new_prio_for_inheritance(waiter->base.prio, new_prio) : new_prio; K_DEBUG("adjusting prio down on mutex %p\n", mutex); key = irq_lock(); adjust_owner_prio(mutex, new_prio); irq_unlock(key); k_sched_unlock(); return -EAGAIN; } void k_mutex_unlock(struct k_mutex *mutex) { int key; __ASSERT(mutex->lock_count > 0, ""); __ASSERT(mutex->owner == _current, ""); _sched_lock(); RECORD_STATE_CHANGE(); mutex->lock_count--; K_DEBUG("mutex %p lock_count: %d\n", mutex, mutex->lock_count); if (mutex->lock_count != 0) { k_sched_unlock(); return; } key = irq_lock(); adjust_owner_prio(mutex, mutex->owner_orig_prio); struct k_thread *new_owner = _unpend_first_thread(&mutex->wait_q); K_DEBUG("new owner of mutex %p: %p (prio: %d)\n", mutex, new_owner, new_owner ? new_owner->base.prio : -1000); if (new_owner) { _abort_thread_timeout(new_owner); _ready_thread(new_owner); irq_unlock(key); _set_thread_return_value(new_owner, 0); /* * new owner is already of higher or equal prio than first * waiter since the wait queue is priority-based: no need to * ajust its priority */ mutex->owner = new_owner; mutex->lock_count++; mutex->owner_orig_prio = new_owner->base.prio; } else { irq_unlock(key); mutex->owner = NULL; } k_sched_unlock(); } |