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Commit 3dfe8aaa authored by Bryan O'Donoghue's avatar Bryan O'Donoghue Committed by Greg Kroah-Hartman
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greybus: loopback: convert loopback wake/sleep to a waitqueue 



Current code will incrementally poll for gb->type == 0 and sleep.
This type of polling strategy wastes cycles.

This patch changes the sleep strategy by introducing a wait-queue which
waits for gb->type != 0 or kthread_should_stop() to wake-up and work or
to wake-up and terminate.

Signed-off-by: default avatarBryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@google.com>
parent c2939f41

drivers/staging/greybus/loopback.c

+17 −13
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ struct gb_loopback { 
	u8 version_minor;



	struct task_struct *task;

	wait_queue_head_t wq;



	int type;

	u32 size;
@@ -113,22 +114,24 @@ static DEVICE_ATTR_RW(field) 
static void gb_loopback_reset_stats(struct gb_loopback *gb);

static void gb_loopback_check_attr(struct gb_loopback *gb)

{

	if (gb->ms_wait > GB_LOOPBACK_MS_WAIT_MAX)

		gb->ms_wait = GB_LOOPBACK_MS_WAIT_MAX;

	if (gb->size > gb->size_max)

		gb->size = gb->size_max;

	gb->error = 0;

	gb->iteration_count = 0;

	gb_loopback_reset_stats(gb);



	switch (gb->type) {

	case GB_LOOPBACK_TYPE_PING:

	case GB_LOOPBACK_TYPE_TRANSFER:

	case GB_LOOPBACK_TYPE_SINK:

		wake_up(&gb->wq);

		break;

	default:

		gb->type = 0;

		break;

	}

	if (gb->ms_wait > GB_LOOPBACK_MS_WAIT_MAX)

		gb->ms_wait = GB_LOOPBACK_MS_WAIT_MAX;

	if (gb->size > gb->size_max)

		gb->size = gb->size_max;

	gb->error = 0;

	gb->iteration_count = 0;

	gb_loopback_reset_stats(gb);

}



/* Time to send and receive one message */
@@ -397,11 +400,12 @@ static int gb_loopback_fn(void *data) 
	struct timeval tlat = {0, 0};

	struct gb_loopback *gb = (struct gb_loopback *)data;



	while (!kthread_should_stop()) {

		if (!gb->type) {

			msleep(1000);

			continue;

		}

	while (1) {

		if (!gb->type)

			wait_event_interruptible(gb->wq, gb->type ||

						 kthread_should_stop());

		if (kthread_should_stop())

			break;

		if (gb->iteration_max) {

			if (gb->iteration_count < gb->iteration_max) {

				gb->iteration_count++;
@@ -429,7 +433,6 @@ static int gb_loopback_fn(void *data) 
		gb->ts = gb->te;

		if (gb->ms_wait)

			msleep(gb->ms_wait);



	}

	return 0;

}
@@ -463,6 +466,7 @@ static int gb_loopback_connection_init(struct gb_connection *connection) 
	gb->size_max -= sizeof(struct gb_loopback_transfer_request);



	gb_loopback_reset_stats(gb);

	init_waitqueue_head(&gb->wq);

	gb->task = kthread_run(gb_loopback_fn, gb, "gb_loopback");

	if (IS_ERR(gb->task)) {

		retval = PTR_ERR(gb->task);