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/block.c b/drivers/mmc/card/block.c
index 3e73be0..646d1a1 100644 (file)
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -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);
        }
 

diff --git a/drivers/mmc/card/queue.c b/drivers/mmc/card/queue.c
index 7dacf27..010888d 100644 (file)
--- 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);
 }
 

diff --git a/drivers/mmc/card/queue.h b/drivers/mmc/card/queue.h
index 47f5532..d09fce6 100644 (file)
--- a/drivers/mmc/card/queue.h
+++ b/drivers/mmc/card/queue.h
@@ -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];

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index f39397f..dc1f27e 100644 (file)
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -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;

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 2ce32fe..8bc8841 100644 (file)
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -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;