Enable kernel wakelocks and timers (0b807371) · Commits · e / os / android_packages_modules_Bluetooth

system/osi/src/alarm.c

+172 −29

Original line number	Diff line number	Diff line
		@@ -22,6 +22,7 @@

		#include <assert.h>
		#include <errno.h>
		#include <fcntl.h>
		#include <inttypes.h>
		#include <malloc.h>
		#include <pthread.h>
		@@ -53,7 +54,6 @@ struct alarm_t {
		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
		@@ -61,7 +61,14 @@ extern bt_os_callouts_t *bt_os_callouts;
		// 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 clockid_t CLOCK_ID_ALARM = CLOCK_BOOTTIME_ALARM;
		static const char *WAKE_LOCK_ID = "bluedroid_timer";
		static const char *WAKE_LOCK_PATH = "/sys/power/wake_lock";
		static const char *WAKE_UNLOCK_PATH = "/sys/power/wake_unlock";
		static ssize_t locked_id_len = -1;
		static pthread_once_t wake_fds_initialized = PTHREAD_ONCE_INIT;
		static int wake_lock_fd = INVALID_FD;
		static int wake_unlock_fd = INVALID_FD;

		// This mutex ensures that the \|alarm_set\|, \|alarm_cancel\|, and alarm callback
		// functions execute serially and not concurrently. As a result, this mutex also
		@@ -69,6 +76,7 @@ static const char *WAKE_LOCK_ID = "bluedroid_timer";
		static pthread_mutex_t monitor;
		static list_t *alarms;
		static timer_t timer;
		static timer_t wakeup_timer;
		static bool timer_set;

		// All alarm callbacks are dispatched from \|callback_thread\|
		@@ -83,11 +91,17 @@ 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);
		static bool timer_create_internal(const clockid_t clock_id, timer_t *timer);
		static void initialize_wake_fds(void);
		static bool acquire_wake_lock(void);
		static bool release_wake_lock(void);

		alarm_t *alarm_new(void) {
		// Make sure we have a list we can insert alarms into.
		if (!alarms && !lazy_initialize())
		if (!alarms && !lazy_initialize()) {
		assert(false); // if initialization failed, we should not continue
		return NULL;
		}

		pthread_mutexattr_t attr;
		pthread_mutexattr_init(&attr);
		@@ -214,39 +228,64 @@ void alarm_cleanup(void) {
		static bool lazy_initialize(void) {
		assert(alarms == NULL);

		// timer_t doesn't have an invalid value so we must track whether
		// the \|timer\| variable is valid ourselves.
		bool timer_initialized = false;
		bool wakeup_timer_initialized = false;

		pthread_mutex_init(&monitor, NULL);

		alarms = list_new(NULL);
		if (!alarms) {
		LOG_ERROR(LOG_TAG, "%s unable to allocate alarm list.", __func__);
		return false;
		goto error;
		}

		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(LOG_TAG, "%s unable to create timer: %s", __func__,
		strerror(errno));
		return false;
		}
		if (!timer_create_internal(CLOCK_ID, &timer))
		goto error;
		timer_initialized = true;

		if (!timer_create_internal(CLOCK_ID_ALARM, &wakeup_timer))
		goto error;
		wakeup_timer_initialized = true;

		alarm_expired = semaphore_new(0);
		if (!alarm_expired) {
		LOG_ERROR(LOG_TAG, "%s unable to create alarm expired semaphore", __func__);
		return false;
		goto error;
		}

		callback_thread_active = true;
		callback_thread = thread_new("alarm_callbacks");
		if (!callback_thread) {
		LOG_ERROR(LOG_TAG, "%s unable to create alarm callback thread.", __func__);
		return false;
		goto error;
		}

		thread_post(callback_thread, callback_dispatch, NULL);
		return true;

		error:
		thread_free(callback_thread);
		callback_thread = NULL;

		callback_thread_active = false;

		semaphore_free(alarm_expired);
		alarm_expired = NULL;

		if (wakeup_timer_initialized)
		timer_delete(wakeup_timer);

		if (timer_initialized)
		timer_delete(timer);

		list_free(alarms);
		alarms = NULL;

		pthread_mutex_destroy(&monitor);

		return false;
		}

		static period_ms_t now(void) {
		@@ -293,41 +332,67 @@ static void schedule_next_instance(alarm_t *alarm, bool force_reschedule) {

		// 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));
		const bool timer_was_set = timer_set;

		// If used in a zeroed state, disarms the timer.
		struct itimerspec timer_time;
		memset(&timer_time, 0, sizeof(timer_time));

		if (list_is_empty(alarms))
		goto done;

		alarm_t *next = list_front(alarms);
		int64_t next_expiration = next->deadline - now();
		const alarm_t *next = list_front(alarms);
		const 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(LOG_TAG, "%s unable to acquire wake lock: %d", __func__, status);
		if (!acquire_wake_lock()) {
		LOG_ERROR(LOG_TAG, "%s unable to acquire wake lock", __func__);
		goto done;
		}
		}

		timer_time.it_value.tv_sec = (next->deadline / 1000);
		timer_time.it_value.tv_nsec = (next->deadline % 1000) * 1000000LL;

		// It is entirely unsafe to call timer_settime(2) with a zeroed timerspec for
		// timers with *_ALARM clock IDs. Although the man page states that the timer
		// would be canceled, the current behavior (as of Linux kernel 3.17) is that
		// the callback is issued immediately. The only way to cancel an *_ALARM timer
		// is to delete the timer. But unfortunately, deleting and re-creating a timer
		// is rather expensive; every timer_create(2) spawns a new thread. So we simply
		// set the timer to fire at the largest possible time.
		//
		// If we've reached this code path, we're going to grab a wake lock and wait for
		// the next timer to fire. In that case, there's no reason to have a pending wakeup
		// timer so we simply cancel it.
		struct itimerspec end_of_time;
		memset(&end_of_time, 0, sizeof(end_of_time));
		end_of_time.it_value.tv_sec = (time_t)(1LL << (sizeof(time_t) * 8 - 2));
		timer_settime(wakeup_timer, TIMER_ABSTIME, &end_of_time, NULL);
		} else {
		// WARNING: do not attempt to use relative timers with *_ALARM clock IDs
		// in kernels before 3.17 unless you have the following patch:
		// https://lkml.org/lkml/2014/7/7/576
		struct itimerspec wakeup_time;
		memset(&wakeup_time, 0, sizeof(wakeup_time));


		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(LOG_TAG, "%s unable to set wake alarm for %" PRId64 "ms.", __func__, next_expiration);
		if (timer_settime(wakeup_timer, TIMER_ABSTIME, &wakeup_time, NULL) == -1)
		LOG_ERROR(LOG_TAG, "%s unable to set wakeup timer: %s",
		__func__, strerror(errno));
		}

		done:
		timer_set = wakeup_time.it_value.tv_sec != 0 \|\| wakeup_time.it_value.tv_nsec != 0;
		timer_set = timer_time.it_value.tv_sec != 0 \|\| timer_time.it_value.tv_nsec != 0;
		if (timer_was_set && !timer_set) {
		bt_os_callouts->release_wake_lock(WAKE_LOCK_ID);
		release_wake_lock();
		}

		if (timer_settime(timer, TIMER_ABSTIME, &wakeup_time, NULL) == -1)
		if (timer_settime(timer, TIMER_ABSTIME, &timer_time, NULL) == -1)
		LOG_ERROR(LOG_TAG, "%s unable to set timer: %s", __func__, strerror(errno));

		// If next expiration was in the past (e.g. short timer that got context switched)
		@@ -401,3 +466,81 @@ static void callback_dispatch(UNUSED_ATTR void *context) {

		LOG_DEBUG(LOG_TAG, "%s Callback thread exited", __func__);
		}

		static void initialize_wake_fds(void) {
		LOG_DEBUG(LOG_TAG, "%s opening wake locks", __func__);

		wake_lock_fd = open(WAKE_LOCK_PATH, O_RDWR \| O_CLOEXEC);
		if (wake_lock_fd == INVALID_FD) {
		LOG_ERROR(LOG_TAG, "%s can't open wake lock %s: %s",
		__func__, WAKE_LOCK_PATH, strerror(errno));
		}

		wake_unlock_fd = open(WAKE_UNLOCK_PATH, O_RDWR \| O_CLOEXEC);
		if (wake_unlock_fd == INVALID_FD) {
		LOG_ERROR(LOG_TAG, "%s can't open wake unlock %s: %s",
		__func__, WAKE_UNLOCK_PATH, strerror(errno));
		}
		}

		static bool acquire_wake_lock(void) {
		pthread_once(&wake_fds_initialized, initialize_wake_fds);

		if (wake_lock_fd == INVALID_FD) {
		LOG_ERROR(LOG_TAG, "%s lock not acquired, invalid fd", __func__);
		return false;
		}

		if (wake_unlock_fd == INVALID_FD) {
		LOG_ERROR(LOG_TAG, "%s not acquiring lock: can't release lock", __func__);
		return false;
		}

		long lock_name_len = strlen(WAKE_LOCK_ID);
		locked_id_len = write(wake_lock_fd, WAKE_LOCK_ID, lock_name_len);
		if (locked_id_len == -1) {
		LOG_ERROR(LOG_TAG, "%s wake lock not acquired: %s",
		__func__, strerror(errno));
		return false;
		} else if (locked_id_len < lock_name_len) {
		// TODO (jamuraa): this is weird. maybe we should release and retry.
		LOG_WARN(LOG_TAG, "%s wake lock truncated to %zd chars",
		__func__, locked_id_len);
		}
		return true;
		}

		static bool release_wake_lock(void) {
		pthread_once(&wake_fds_initialized, initialize_wake_fds);

		if (wake_unlock_fd == INVALID_FD) {
		LOG_ERROR(LOG_TAG, "%s lock not released, invalid fd", __func__);
		return false;
		}

		ssize_t wrote_name_len = write(wake_unlock_fd, WAKE_LOCK_ID, locked_id_len);
		if (wrote_name_len == -1) {
		LOG_ERROR(LOG_TAG, "%s can't release wake lock: %s",
		__func__, strerror(errno));
		} else if (wrote_name_len < locked_id_len) {
		LOG_ERROR(LOG_TAG, "%s lock release only wrote %zd, assuming released",
		__func__, wrote_name_len);
		}
		return true;
		}

		static bool timer_create_internal(const clockid_t clock_id, timer_t *timer) {
		assert(timer != NULL);

		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(LOG_TAG, "%s unable to create timer with clock %d: %s",
		__func__, clock_id, strerror(errno));
		return false;
		}

		return true;
		}