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mmc: queue: Fix queue thread wake-up

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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: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Harjani Ritesh <riteshh@codeaurora.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
This commit is contained in:
Adrian Hunter 2016-11-29 12:09:10 +02:00 committed by Ulf Hansson
parent 5be80375f5
commit e0097cf5f2
5 changed files with 22 additions and 29 deletions
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7
drivers/mmc/card/block.c
View file

@ -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);
}

35
drivers/mmc/card/queue.c
View file

@ -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 (cntx->is_waiting_last_req) {
cntx->is_new_req = true;
wake_up_interruptible(&cntx->wait);
}
if (mq->asleep)
wake_up_process(mq->thread);
}

1
drivers/mmc/card/queue.h
View file

@ -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];

6
drivers/mmc/core/core.c
View file

@ -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;

2
include/linux/mmc/host.h
View file

@ -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;