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: 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>
diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index 7dacf27..010888d 100644
--- a/drivers/mmc/card/queue.c
+++ b/drivers/mmc/card/queue.c
@@ -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);
}