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Commit e0097cf5 authored by Adrian Hunter's avatar Adrian Hunter Committed by Ulf Hansson
Browse files

mmc: queue: Fix queue thread wake-up 



The only time the driver sleeps expecting to be woken upon the arrival of
a new request, is when the dispatch queue is empty. The only time that it
is known whether the dispatch queue is empty is after NULL is returned
from blk_fetch_request() while under the queue lock.

Recognizing those facts, simplify the synchronization between the queue
thread and the request function. A couple of flags tell the request
function what to do, and the queue lock and barriers associated with
wake-ups ensure synchronization.

The result is simpler and allows the removal of the context_info lock.

Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Reviewed-by: default avatarHarjani Ritesh <riteshh@codeaurora.org>
Signed-off-by: default avatarUlf Hansson <ulf.hansson@linaro.org>
parent 5be80375

drivers/mmc/card/block.c

+0 −7
Original line number Diff line number Diff line
@@ -1758,8 +1758,6 @@ int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req) 
	int ret;

	struct mmc_blk_data *md = mq->blkdata;

	struct mmc_card *card = md->queue.card;

	struct mmc_host *host = card->host;

	unsigned long flags;

	bool req_is_special = mmc_req_is_special(req);



	if (req && !mq->mqrq_prev->req)
@@ -1792,11 +1790,6 @@ int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req) 
			mmc_blk_issue_rw_rq(mq, NULL);

		ret = mmc_blk_issue_flush(mq, req);

	} else {

		if (!req && host->areq) {

			spin_lock_irqsave(&host->context_info.lock, flags);

			host->context_info.is_waiting_last_req = true;

			spin_unlock_irqrestore(&host->context_info.lock, flags);

		}

		ret = mmc_blk_issue_rw_rq(mq, req);

	}

drivers/mmc/card/queue.c

+21 −14
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ static int mmc_queue_thread(void *d) 
{

	struct mmc_queue *mq = d;

	struct request_queue *q = mq->queue;

	struct mmc_context_info *cntx = &mq->card->host->context_info;



	current->flags |= PF_MEMALLOC;
@@ -63,6 +64,19 @@ static int mmc_queue_thread(void *d) 
		spin_lock_irq(q->queue_lock);

		set_current_state(TASK_INTERRUPTIBLE);

		req = blk_fetch_request(q);

		mq->asleep = false;

		cntx->is_waiting_last_req = false;

		cntx->is_new_req = false;

		if (!req) {

			/*

			 * Dispatch queue is empty so set flags for

			 * mmc_request_fn() to wake us up.

			 */

			if (mq->mqrq_prev->req)

				cntx->is_waiting_last_req = true;

			else

				mq->asleep = true;

		}

		mq->mqrq_cur->req = req;

		spin_unlock_irq(q->queue_lock);
@@ -115,7 +129,6 @@ static void mmc_request_fn(struct request_queue *q) 
{

	struct mmc_queue *mq = q->queuedata;

	struct request *req;

	unsigned long flags;

	struct mmc_context_info *cntx;



	if (!mq) {
@@ -127,19 +140,13 @@ static void mmc_request_fn(struct request_queue *q) 
	}



	cntx = &mq->card->host->context_info;

	if (!mq->mqrq_cur->req && mq->mqrq_prev->req) {

		/*

		 * New MMC request arrived when MMC thread may be

		 * blocked on the previous request to be complete

		 * with no current request fetched

		 */

		spin_lock_irqsave(&cntx->lock, flags);



	if (cntx->is_waiting_last_req) {

		cntx->is_new_req = true;

		wake_up_interruptible(&cntx->wait);

	}

		spin_unlock_irqrestore(&cntx->lock, flags);

	} else if (!mq->mqrq_cur->req && !mq->mqrq_prev->req)



	if (mq->asleep)

		wake_up_process(mq->thread);

}

drivers/mmc/card/queue.h

+1 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ struct mmc_queue { 
	unsigned int		flags;

#define MMC_QUEUE_SUSPENDED	(1 << 0)

#define MMC_QUEUE_NEW_REQUEST	(1 << 1)

	bool			asleep;

	struct mmc_blk_data	*blkdata;

	struct request_queue	*queue;

	struct mmc_queue_req	mqrq[2];

drivers/mmc/core/core.c

+0 −6
Original line number Diff line number Diff line
@@ -504,18 +504,14 @@ static enum mmc_blk_status mmc_wait_for_data_req_done(struct mmc_host *host, 
	struct mmc_command *cmd;

	struct mmc_context_info *context_info = &host->context_info;

	enum mmc_blk_status status;

	unsigned long flags;



	while (1) {

		wait_event_interruptible(context_info->wait,

				(context_info->is_done_rcv ||

				 context_info->is_new_req));

		spin_lock_irqsave(&context_info->lock, flags);

		context_info->is_waiting_last_req = false;

		spin_unlock_irqrestore(&context_info->lock, flags);

		if (context_info->is_done_rcv) {

			context_info->is_done_rcv = false;

			context_info->is_new_req = false;

			cmd = mrq->cmd;



			if (!cmd->error || !cmd->retries ||
@@ -534,7 +530,6 @@ static enum mmc_blk_status mmc_wait_for_data_req_done(struct mmc_host *host, 
				continue; /* wait for done/new event again */

			}

		} else if (context_info->is_new_req) {

			context_info->is_new_req = false;

			if (!next_req)

				return MMC_BLK_NEW_REQUEST;

		}
@@ -3016,7 +3011,6 @@ void mmc_unregister_pm_notifier(struct mmc_host *host) 
 */

void mmc_init_context_info(struct mmc_host *host)

{

	spin_lock_init(&host->context_info.lock);

	host->context_info.is_new_req = false;

	host->context_info.is_done_rcv = false;

	host->context_info.is_waiting_last_req = false;

include/linux/mmc/host.h

+0 −2
Original line number Diff line number Diff line
@@ -197,14 +197,12 @@ struct mmc_slot { 
 * @is_new_req		wake up reason was new request

 * @is_waiting_last_req	mmc context waiting for single running request

 * @wait		wait queue

 * @lock		lock to protect data fields

 */

struct mmc_context_info {

	bool			is_done_rcv;

	bool			is_new_req;

	bool			is_waiting_last_req;

	wait_queue_head_t	wait;

	spinlock_t		lock;

};



struct regulator;