For completing any block request, MMC block driver is calling:
spin_lock_irq(queue)
__blk_end_request()
spin_unlock_irq(queue)
But if we analyze the sources of latency in kernel using ftrace,
__blk_end_request() function at times may take up to 6.5ms with
spinlock held and irq disabled.
__blk_end_request() calls couple of functions and ftrace output
shows that blk_update_bidi_request() function is almost taking 6ms.
There are 2 function to end the current request: ___blk_end_request()
and blk_end_request(). Both these functions do same thing except
that blk_end_request() function doesn't take up the spinlock
while calling the blk_update_bidi_request().
This patch replaces all __blk_end_request() calls with
blk_end_request() and __blk_end_request_all() calls with
blk_end_request_all().
Testing done: 20 process concurrent read/write on sd card
and eMMC. Ran this test for almost a day on multicore system
and no errors observed.
Signed-off-by: Subhash Jadavani <subhashj@xxxxxxxxxxxxxx>
---
drivers/mmc/card/block.c | 36 +++++++++---------------------------
1 files changed, 9 insertions(+), 27 deletions(-)
diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index b180965..437471a 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -861,9 +861,7 @@ out:
goto retry;
if (!err)
mmc_blk_reset_success(md, type);
- spin_lock_irq(&md->lock);
- __blk_end_request(req, err, blk_rq_bytes(req));
- spin_unlock_irq(&md->lock);
+ blk_end_request(req, err, blk_rq_bytes(req));
return err ? 0 : 1;
}
@@ -923,9 +921,7 @@ out:
goto retry;
if (!err)
mmc_blk_reset_success(md, type);
- spin_lock_irq(&md->lock);
- __blk_end_request(req, err, blk_rq_bytes(req));
- spin_unlock_irq(&md->lock);
+ blk_end_request(req, err, blk_rq_bytes(req));
return err ? 0 : 1;
}
@@ -940,9 +936,7 @@ static int mmc_blk_issue_flush(struct mmc_queue *mq, struct request *req)
if (ret)
ret = -EIO;
- spin_lock_irq(&md->lock);
- __blk_end_request_all(req, ret);
- spin_unlock_irq(&md->lock);
+ blk_end_request_all(req, ret);
return ret ? 0 : 1;
}
@@ -1241,14 +1235,10 @@ static int mmc_blk_cmd_err(struct mmc_blk_data *md, struct mmc_card *card,
blocks = mmc_sd_num_wr_blocks(card);
if (blocks != (u32)-1) {
- spin_lock_irq(&md->lock);
- ret = __blk_end_request(req, 0, blocks << 9);
- spin_unlock_irq(&md->lock);
+ ret = blk_end_request(req, 0, blocks << 9);
}
} else {
- spin_lock_irq(&md->lock);
- ret = __blk_end_request(req, 0, brq->data.bytes_xfered);
- spin_unlock_irq(&md->lock);
+ ret = blk_end_request(req, 0, brq->data.bytes_xfered);
}
return ret;
}
@@ -1290,10 +1280,8 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
* A block was successfully transferred.
*/
mmc_blk_reset_success(md, type);
- spin_lock_irq(&md->lock);
- ret = __blk_end_request(req, 0,
+ ret = blk_end_request(req, 0,
brq->data.bytes_xfered);
- spin_unlock_irq(&md->lock);
/*
* If the blk_end_request function returns non-zero even
* though all data has been transferred and no errors
@@ -1343,10 +1331,8 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
* time, so we only reach here after trying to
* read a single sector.
*/
- spin_lock_irq(&md->lock);
- ret = __blk_end_request(req, -EIO,
+ ret = blk_end_request(req, -EIO,
brq->data.blksz);
- spin_unlock_irq(&md->lock);
if (!ret)
goto start_new_req;
break;
@@ -1367,12 +1353,10 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq, struct request *rqc)
return 1;
cmd_abort:
- spin_lock_irq(&md->lock);
if (mmc_card_removed(card))
req->cmd_flags |= REQ_QUIET;
while (ret)
- ret = __blk_end_request(req, -EIO, blk_rq_cur_bytes(req));
- spin_unlock_irq(&md->lock);
+ ret = blk_end_request(req, -EIO, blk_rq_cur_bytes(req));
start_new_req:
if (rqc) {
@@ -1396,9 +1380,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
ret = mmc_blk_part_switch(card, md);
if (ret) {
if (req) {
- spin_lock_irq(&md->lock);
- __blk_end_request_all(req, -EIO);
- spin_unlock_irq(&md->lock);
+ blk_end_request_all(req, -EIO);
}
ret = 0;
goto out;
--
1.7.1.1
--
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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