208 lines
7.4 KiB
C
208 lines
7.4 KiB
C
// Copyright 2015-2016 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include <sys/lock.h>
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#include <stdlib.h>
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#include <sys/reent.h>
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#include "esp_attr.h"
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#include "soc/cpu.h"
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#include "freertos/FreeRTOS.h"
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#include "freertos/semphr.h"
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#include "freertos/portmacro.h"
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#include "freertos/task.h"
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#include "freertos/portable.h"
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/* Notes on our newlib lock implementation:
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*
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* - Use FreeRTOS mutex semaphores as locks.
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* - lock_t is int, but we store an xSemaphoreHandle there.
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* - Locks are no-ops until the FreeRTOS scheduler is running.
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* - Due to this, locks need to be lazily initialised the first time
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* they are acquired. Initialisation/deinitialisation of locks is
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* protected by lock_init_spinlock.
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* - Race conditions around lazy initialisation (via lock_acquire) are
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* protected against.
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* - Anyone calling lock_close is reponsible for ensuring noone else
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* is holding the lock at this time.
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* - Race conditions between lock_close & lock_init (for the same lock)
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* are the responsibility of the caller.
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*/
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static portMUX_TYPE lock_init_spinlock = portMUX_INITIALIZER_UNLOCKED;
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/* Initialise the given lock by allocating a new mutex semaphore
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as the _lock_t value.
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*/
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static void IRAM_ATTR lock_init_generic(_lock_t *lock, uint8_t mutex_type) {
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portENTER_CRITICAL(&lock_init_spinlock);
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if (xTaskGetSchedulerState() == taskSCHEDULER_NOT_STARTED) {
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/* nothing to do until the scheduler is running */
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*lock = 0; /* ensure lock is zeroed out, in case it's an automatic variable */
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portEXIT_CRITICAL(&lock_init_spinlock);
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return;
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}
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if (*lock) {
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/* Lock already initialised (either we didn't check earlier,
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or it got initialised while we were waiting for the
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spinlock.) */
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}
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else
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{
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/* Create a new semaphore
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this is a bit of an API violation, as we're calling the
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private function xQueueCreateMutex(x) directly instead of
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the xSemaphoreCreateMutex / xSemaphoreCreateRecursiveMutex
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wrapper functions...
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The better alternative would be to pass pointers to one of
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the two xSemaphoreCreate___Mutex functions, but as FreeRTOS
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implements these as macros instead of inline functions
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(*party like it's 1998!*) it's not possible to do this
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without writing wrappers. Doing it this way seems much less
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spaghetti-like.
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*/
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xSemaphoreHandle new_sem = xQueueCreateMutex(mutex_type);
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if (!new_sem) {
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abort(); /* No more semaphores available or OOM */
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}
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*lock = (_lock_t)new_sem;
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}
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portEXIT_CRITICAL(&lock_init_spinlock);
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}
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void IRAM_ATTR _lock_init(_lock_t *lock) {
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lock_init_generic(lock, queueQUEUE_TYPE_MUTEX);
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}
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void IRAM_ATTR _lock_init_recursive(_lock_t *lock) {
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lock_init_generic(lock, queueQUEUE_TYPE_RECURSIVE_MUTEX);
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}
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/* Free the mutex semaphore pointed to by *lock, and zero it out.
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Note that FreeRTOS doesn't account for deleting mutexes while they
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are held, and neither do we... so take care not to delete newlib
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locks while they may be held by other tasks!
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*/
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void IRAM_ATTR _lock_close(_lock_t *lock) {
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portENTER_CRITICAL(&lock_init_spinlock);
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if (*lock) {
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xSemaphoreHandle h = (xSemaphoreHandle)(*lock);
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#if (INCLUDE_xSemaphoreGetMutexHolder == 1)
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configASSERT(xSemaphoreGetMutexHolder(h) == NULL); /* mutex should not be held */
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#endif
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vSemaphoreDelete(h);
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*lock = 0;
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}
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portEXIT_CRITICAL(&lock_init_spinlock);
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}
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/* Acquire the mutex semaphore for lock. wait up to delay ticks.
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mutex_type is queueQUEUE_TYPE_RECURSIVE_MUTEX or queueQUEUE_TYPE_MUTEX
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*/
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static int IRAM_ATTR lock_acquire_generic(_lock_t *lock, uint32_t delay, uint8_t mutex_type) {
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xSemaphoreHandle h = (xSemaphoreHandle)(*lock);
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if (!h) {
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if (xTaskGetSchedulerState() == taskSCHEDULER_NOT_STARTED) {
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return 0; /* locking is a no-op before scheduler is up, so this "succeeds" */
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}
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/* lazy initialise lock - might have had a static initializer in newlib (that we don't use),
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or _lock_init might have been called before the scheduler was running... */
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lock_init_generic(lock, mutex_type);
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h = (xSemaphoreHandle)(*lock);
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configASSERT(h != NULL);
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}
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BaseType_t success;
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if (xPortInIsrContext()) {
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/* In ISR Context */
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if (mutex_type == queueQUEUE_TYPE_RECURSIVE_MUTEX) {
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abort(); /* recursive mutexes make no sense in ISR context */
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}
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BaseType_t higher_task_woken = false;
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success = xSemaphoreTakeFromISR(h, &higher_task_woken);
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if (!success && delay > 0) {
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abort(); /* Tried to block on mutex from ISR, couldn't... rewrite your program to avoid libc interactions in ISRs! */
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}
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if (higher_task_woken) {
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portYIELD_FROM_ISR();
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}
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}
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else {
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/* In task context */
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if (mutex_type == queueQUEUE_TYPE_RECURSIVE_MUTEX) {
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success = xSemaphoreTakeRecursive(h, delay);
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} else {
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success = xSemaphoreTake(h, delay);
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}
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}
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return (success == pdTRUE) ? 0 : -1;
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}
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void IRAM_ATTR _lock_acquire(_lock_t *lock) {
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lock_acquire_generic(lock, portMAX_DELAY, queueQUEUE_TYPE_MUTEX);
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}
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void IRAM_ATTR _lock_acquire_recursive(_lock_t *lock) {
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lock_acquire_generic(lock, portMAX_DELAY, queueQUEUE_TYPE_RECURSIVE_MUTEX);
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}
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int IRAM_ATTR _lock_try_acquire(_lock_t *lock) {
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return lock_acquire_generic(lock, 0, queueQUEUE_TYPE_MUTEX);
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}
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int IRAM_ATTR _lock_try_acquire_recursive(_lock_t *lock) {
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return lock_acquire_generic(lock, 0, queueQUEUE_TYPE_RECURSIVE_MUTEX);
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}
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/* Release the mutex semaphore for lock.
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mutex_type is queueQUEUE_TYPE_RECURSIVE_MUTEX or queueQUEUE_TYPE_MUTEX
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*/
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static void IRAM_ATTR lock_release_generic(_lock_t *lock, uint8_t mutex_type) {
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xSemaphoreHandle h = (xSemaphoreHandle)(*lock);
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if (h == NULL) {
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/* This is probably because the scheduler isn't running yet,
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or the scheduler just started running and some code was
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"holding" a not-yet-initialised lock... */
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return;
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}
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if (xPortInIsrContext()) {
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if (mutex_type == queueQUEUE_TYPE_RECURSIVE_MUTEX) {
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abort(); /* indicates logic bug, it shouldn't be possible to lock recursively in ISR */
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}
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BaseType_t higher_task_woken = false;
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xSemaphoreGiveFromISR(h, &higher_task_woken);
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if (higher_task_woken) {
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portYIELD_FROM_ISR();
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}
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} else {
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if (mutex_type == queueQUEUE_TYPE_RECURSIVE_MUTEX) {
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xSemaphoreGiveRecursive(h);
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} else {
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xSemaphoreGive(h);
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}
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}
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}
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void IRAM_ATTR _lock_release(_lock_t *lock) {
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lock_release_generic(lock, queueQUEUE_TYPE_MUTEX);
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}
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void IRAM_ATTR _lock_release_recursive(_lock_t *lock) {
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lock_release_generic(lock, queueQUEUE_TYPE_RECURSIVE_MUTEX);
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}
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