| /****************************************************************************** |
| * |
| * Copyright (C) 2014 Google, Inc. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at: |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| ******************************************************************************/ |
| |
| #define LOG_TAG "bt_osi_alarm" |
| |
| #include <assert.h> |
| #include <errno.h> |
| #include <hardware/bluetooth.h> |
| #include <inttypes.h> |
| #include <malloc.h> |
| #include <string.h> |
| #include <signal.h> |
| #include <time.h> |
| #include <pthread.h> |
| |
| #include "osi/include/alarm.h" |
| #include "osi/include/allocator.h" |
| #include "osi/include/list.h" |
| #include "osi/include/log.h" |
| #include "osi/include/osi.h" |
| #include "osi/include/semaphore.h" |
| #include "osi/include/thread.h" |
| |
| struct alarm_t { |
| // The lock is held while the callback for this alarm is being executed. |
| // It allows us to release the coarse-grained monitor lock while a potentially |
| // long-running callback is executing. |alarm_cancel| uses this lock to provide |
| // a guarantee to its caller that the callback will not be in progress when it |
| // returns. |
| pthread_mutex_t callback_lock; |
| period_ms_t created; |
| period_ms_t period; |
| period_ms_t deadline; |
| bool is_periodic; |
| alarm_callback_t callback; |
| void *data; |
| }; |
| |
| extern bt_os_callouts_t *bt_os_callouts; |
| |
| // If the next wakeup time is less than this threshold, we should acquire |
| // a wakelock instead of setting a wake alarm so we're not bouncing in |
| // and out of suspend frequently. This value is externally visible to allow |
| // unit tests to run faster. It should not be modified by production code. |
| int64_t TIMER_INTERVAL_FOR_WAKELOCK_IN_MS = 3000; |
| static const clockid_t CLOCK_ID = CLOCK_BOOTTIME; |
| static const char *WAKE_LOCK_ID = "bluedroid_timer"; |
| |
| // This mutex ensures that the |alarm_set|, |alarm_cancel|, and alarm callback |
| // functions execute serially and not concurrently. As a result, this mutex also |
| // protects the |alarms| list. |
| static pthread_mutex_t monitor; |
| static list_t *alarms; |
| static timer_t timer; |
| static bool timer_set; |
| |
| // All alarm callbacks are dispatched from |callback_thread| |
| static thread_t *callback_thread; |
| static bool callback_thread_active; |
| static semaphore_t *alarm_expired; |
| |
| static bool lazy_initialize(void); |
| static period_ms_t now(void); |
| static void alarm_set_internal(alarm_t *alarm, period_ms_t deadline, alarm_callback_t cb, void *data, bool is_periodic); |
| static void schedule_next_instance(alarm_t *alarm, bool force_reschedule); |
| static void reschedule_root_alarm(void); |
| static void timer_callback(void *data); |
| static void callback_dispatch(void *context); |
| |
| alarm_t *alarm_new(void) { |
| // Make sure we have a list we can insert alarms into. |
| if (!alarms && !lazy_initialize()) |
| return NULL; |
| |
| pthread_mutexattr_t attr; |
| pthread_mutexattr_init(&attr); |
| |
| alarm_t *ret = osi_calloc(sizeof(alarm_t)); |
| if (!ret) { |
| LOG_ERROR("%s unable to allocate memory for alarm.", __func__); |
| goto error; |
| } |
| |
| // Make this a recursive mutex to make it safe to call |alarm_cancel| from |
| // within the callback function of the alarm. |
| int error = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE); |
| if (error) { |
| LOG_ERROR("%s unable to create a recursive mutex: %s", __func__, strerror(error)); |
| goto error; |
| } |
| |
| error = pthread_mutex_init(&ret->callback_lock, &attr); |
| if (error) { |
| LOG_ERROR("%s unable to initialize mutex: %s", __func__, strerror(error)); |
| goto error; |
| } |
| |
| pthread_mutexattr_destroy(&attr); |
| return ret; |
| |
| error:; |
| pthread_mutexattr_destroy(&attr); |
| osi_free(ret); |
| return NULL; |
| } |
| |
| void alarm_free(alarm_t *alarm) { |
| if (!alarm) |
| return; |
| |
| alarm_cancel(alarm); |
| pthread_mutex_destroy(&alarm->callback_lock); |
| osi_free(alarm); |
| } |
| |
| void alarm_set(alarm_t *alarm, period_ms_t deadline, alarm_callback_t cb, void *data) { |
| alarm_set_internal(alarm, deadline, cb, data, false); |
| } |
| |
| void alarm_set_periodic(alarm_t *alarm, period_ms_t period, alarm_callback_t cb, void *data) { |
| alarm_set_internal(alarm, period, cb, data, true); |
| } |
| |
| // Runs in exclusion with alarm_cancel and timer_callback. |
| static void alarm_set_internal(alarm_t *alarm, period_ms_t period, alarm_callback_t cb, void *data, bool is_periodic) { |
| assert(alarms != NULL); |
| assert(alarm != NULL); |
| assert(cb != NULL); |
| |
| pthread_mutex_lock(&monitor); |
| |
| alarm->created = now(); |
| alarm->is_periodic = is_periodic; |
| alarm->period = period; |
| alarm->callback = cb; |
| alarm->data = data; |
| |
| schedule_next_instance(alarm, false); |
| |
| pthread_mutex_unlock(&monitor); |
| } |
| |
| void alarm_cancel(alarm_t *alarm) { |
| assert(alarms != NULL); |
| assert(alarm != NULL); |
| |
| pthread_mutex_lock(&monitor); |
| |
| bool needs_reschedule = (!list_is_empty(alarms) && list_front(alarms) == alarm); |
| |
| list_remove(alarms, alarm); |
| alarm->deadline = 0; |
| alarm->callback = NULL; |
| alarm->data = NULL; |
| |
| if (needs_reschedule) |
| reschedule_root_alarm(); |
| |
| pthread_mutex_unlock(&monitor); |
| |
| // If the callback for |alarm| is in progress, wait here until it completes. |
| pthread_mutex_lock(&alarm->callback_lock); |
| pthread_mutex_unlock(&alarm->callback_lock); |
| } |
| |
| void alarm_shutdown(void) { |
| // If lazy_initialize never ran there is nothing to do |
| if (!alarms) |
| return; |
| |
| callback_thread_active = false; |
| semaphore_post(alarm_expired); |
| thread_free(callback_thread); |
| callback_thread = NULL; |
| |
| semaphore_free(alarm_expired); |
| alarm_expired = NULL; |
| timer_delete(&timer); |
| } |
| |
| void alarm_cleanup(void) { |
| // If lazy_initialize never ran there is nothing to do |
| if (!alarms) |
| return; |
| |
| list_free(alarms); |
| alarms = NULL; |
| |
| pthread_mutex_destroy(&monitor); |
| } |
| |
| static bool lazy_initialize(void) { |
| assert(alarms == NULL); |
| |
| pthread_mutex_init(&monitor, NULL); |
| |
| alarms = list_new(NULL); |
| if (!alarms) { |
| LOG_ERROR("%s unable to allocate alarm list.", __func__); |
| return false; |
| } |
| |
| struct sigevent sigevent; |
| memset(&sigevent, 0, sizeof(sigevent)); |
| sigevent.sigev_notify = SIGEV_THREAD; |
| sigevent.sigev_notify_function = (void (*)(union sigval))timer_callback; |
| if (timer_create(CLOCK_ID, &sigevent, &timer) == -1) { |
| LOG_ERROR("%s unable to create timer: %s", __func__, strerror(errno)); |
| return false; |
| } |
| |
| alarm_expired = semaphore_new(0); |
| if (!alarm_expired) { |
| LOG_ERROR("%s unable to create alarm expired semaphore", __func__); |
| return false; |
| } |
| |
| callback_thread_active = true; |
| callback_thread = thread_new("alarm_callbacks"); |
| if (!callback_thread) { |
| LOG_ERROR("%s unable to create alarm callback thread.", __func__); |
| return false; |
| } |
| |
| thread_post(callback_thread, callback_dispatch, NULL); |
| return true; |
| } |
| |
| static period_ms_t now(void) { |
| assert(alarms != NULL); |
| |
| struct timespec ts; |
| if (clock_gettime(CLOCK_ID, &ts) == -1) { |
| LOG_ERROR("%s unable to get current time: %s", __func__, strerror(errno)); |
| return 0; |
| } |
| |
| return (ts.tv_sec * 1000LL) + (ts.tv_nsec / 1000000LL); |
| } |
| |
| // Must be called with monitor held |
| static void schedule_next_instance(alarm_t *alarm, bool force_reschedule) { |
| // If the alarm is currently set and it's at the start of the list, |
| // we'll need to re-schedule since we've adjusted the earliest deadline. |
| bool needs_reschedule = (!list_is_empty(alarms) && list_front(alarms) == alarm); |
| if (alarm->callback) |
| list_remove(alarms, alarm); |
| |
| // Calculate the next deadline for this alarm |
| period_ms_t just_now = now(); |
| period_ms_t ms_into_period = alarm->is_periodic ? ((just_now - alarm->created) % alarm->period) : 0; |
| alarm->deadline = just_now + (alarm->period - ms_into_period); |
| |
| // Add it into the timer list sorted by deadline (earliest deadline first). |
| if (list_is_empty(alarms) || ((alarm_t *)list_front(alarms))->deadline >= alarm->deadline) |
| list_prepend(alarms, alarm); |
| else |
| for (list_node_t *node = list_begin(alarms); node != list_end(alarms); node = list_next(node)) { |
| list_node_t *next = list_next(node); |
| if (next == list_end(alarms) || ((alarm_t *)list_node(next))->deadline >= alarm->deadline) { |
| list_insert_after(alarms, node, alarm); |
| break; |
| } |
| } |
| |
| // If the new alarm has the earliest deadline, we need to re-evaluate our schedule. |
| if (force_reschedule || needs_reschedule || (!list_is_empty(alarms) && list_front(alarms) == alarm)) |
| reschedule_root_alarm(); |
| } |
| |
| // NOTE: must be called with monitor lock. |
| static void reschedule_root_alarm(void) { |
| bool timer_was_set = timer_set; |
| assert(alarms != NULL); |
| |
| // If used in a zeroed state, disarms the timer |
| struct itimerspec wakeup_time; |
| memset(&wakeup_time, 0, sizeof(wakeup_time)); |
| |
| if (list_is_empty(alarms)) |
| goto done; |
| |
| alarm_t *next = list_front(alarms); |
| int64_t next_expiration = next->deadline - now(); |
| if (next_expiration < TIMER_INTERVAL_FOR_WAKELOCK_IN_MS) { |
| if (!timer_set) { |
| int status = bt_os_callouts->acquire_wake_lock(WAKE_LOCK_ID); |
| if (status != BT_STATUS_SUCCESS) { |
| LOG_ERROR("%s unable to acquire wake lock: %d", __func__, status); |
| goto done; |
| } |
| } |
| |
| wakeup_time.it_value.tv_sec = (next->deadline / 1000); |
| wakeup_time.it_value.tv_nsec = (next->deadline % 1000) * 1000000LL; |
| } else { |
| if (!bt_os_callouts->set_wake_alarm(next_expiration, true, timer_callback, NULL)) |
| LOG_ERROR("%s unable to set wake alarm for %" PRId64 "ms.", __func__, next_expiration); |
| } |
| |
| done: |
| timer_set = wakeup_time.it_value.tv_sec != 0 || wakeup_time.it_value.tv_nsec != 0; |
| if (timer_was_set && !timer_set) { |
| bt_os_callouts->release_wake_lock(WAKE_LOCK_ID); |
| } |
| |
| if (timer_settime(timer, TIMER_ABSTIME, &wakeup_time, NULL) == -1) |
| LOG_ERROR("%s unable to set timer: %s", __func__, strerror(errno)); |
| |
| // If next expiration was in the past (e.g. short timer that got context switched) |
| // then the timer might have diarmed itself. Detect this case and work around it |
| // by manually signalling the |alarm_expired| semaphore. |
| // |
| // It is possible that the timer was actually super short (a few milliseconds) |
| // and the timer expired normally before we called |timer_gettime|. Worst case, |
| // |alarm_expired| is signaled twice for that alarm. Nothing bad should happen in |
| // that case though since the callback dispatch function checks to make sure the |
| // timer at the head of the list actually expired. |
| if (timer_set) { |
| struct itimerspec time_to_expire; |
| timer_gettime(timer, &time_to_expire); |
| if (time_to_expire.it_value.tv_sec == 0 && time_to_expire.it_value.tv_nsec == 0) { |
| LOG_ERROR("%s alarm expiration too close for posix timers, switching to guns", __func__); |
| semaphore_post(alarm_expired); |
| } |
| } |
| } |
| |
| // Callback function for wake alarms and our posix timer |
| static void timer_callback(UNUSED_ATTR void *ptr) { |
| semaphore_post(alarm_expired); |
| } |
| |
| // Function running on |callback_thread| that dispatches alarm callbacks upon |
| // alarm expiration, which is signaled using |alarm_expired|. |
| static void callback_dispatch(UNUSED_ATTR void *context) { |
| while (true) { |
| semaphore_wait(alarm_expired); |
| if (!callback_thread_active) |
| break; |
| |
| pthread_mutex_lock(&monitor); |
| alarm_t *alarm; |
| |
| // Take into account that the alarm may get cancelled before we get to it. |
| // We're done here if there are no alarms or the alarm at the front is in |
| // the future. Release the monitor lock and exit right away since there's |
| // nothing left to do. |
| if (list_is_empty(alarms) || (alarm = list_front(alarms))->deadline > now()) { |
| reschedule_root_alarm(); |
| pthread_mutex_unlock(&monitor); |
| continue; |
| } |
| |
| list_remove(alarms, alarm); |
| |
| alarm_callback_t callback = alarm->callback; |
| void *data = alarm->data; |
| |
| if (alarm->is_periodic) { |
| schedule_next_instance(alarm, true); |
| } else { |
| reschedule_root_alarm(); |
| |
| alarm->deadline = 0; |
| alarm->callback = NULL; |
| alarm->data = NULL; |
| } |
| |
| // Downgrade lock. |
| pthread_mutex_lock(&alarm->callback_lock); |
| pthread_mutex_unlock(&monitor); |
| |
| callback(data); |
| |
| pthread_mutex_unlock(&alarm->callback_lock); |
| } |
| |
| LOG_DEBUG("%s Callback thread exited", __func__); |
| } |