On 31/07/18 19:25, Ming Lei wrote:
> Hi Peter,
>
> On Tue, Jul 31, 2018 at 08:47:45AM -0400, Peter Geis wrote:
>> Good Morning,
>>
>> On 07/30/2018 09:38 PM, Ming Lei wrote:
>>> Hi Peter,
>>>
>>> Thanks for collecting the log.
>>>
>>> On Mon, Jul 30, 2018 at 02:55:42PM -0400, Peter Geis wrote:
>>>>
>>>>
>>>> On 07/28/2018 09:37 AM, Ming Lei wrote:
>>>
>>> ...
>>>
>>>> [ 10.887209] systemd--112 0.n.1 2411122us : blk_mq_make_request: make
>>>> rq -1
>>>> [ 10.890274] kworker/-98 0...1 2411506us : blk_mq_free_request:
>>>> complete: rq -1
>>>> [ 10.893313] systemd--107 0...1 2412025us : blk_mq_make_request: make
>>>> rq -1
>>>> [ 10.896354] systemd--107 0.... 2412323us : mmc_mq_queue_rq: queue rq
>>>> -1, 0
>>>> [ 10.899388] systemd--107 0.... 2412327us :
>>>> blk_mq_try_issue_list_directly: issue direct: rq -1, ret 0
>>>> [ 10.902463] (direxec-111 1...1 2413829us : blk_mq_make_request: make
>>>> rq -1
>>>> [ 10.905513] systemd--114 1...1 2415159us : blk_mq_make_request: make
>>>> rq -1
>>>
>>> Above is the most interesting part in the log. MMC sets hw queue depth
>>> as 1, and you are using none scheduler, that means the max number of
>>> in-flight requests should be one, but the above log shows that there may
>>> be 3 in-flight requests.
>>
>> That's odd, I have CFQ set as the default, is something changing this during
>> boot?
>> CONFIG_CFQ_GROUP_IOSCHED=y
>> CONFIG_DEFAULT_IOSCHED="cfq"
>
> No, now mmc has been converted to blk-mq, and the default mq io sched
> should have been mq-deadline for mmc, but not sure why it is none in
> your case.
>
>>
>>>
>>> That seems really weird, but it shouldn't be related with my two patches,
>>> which won't change the tag allocation behaviour at all. However, what matters
>>> may be that the patch speeds up the request dispatch. Maybe one bug
>>> in lib/sbitmap.c block/blk-mq-tag.c.
>>>
>>> Unfortunately rq->tag wasn't shown in the log because I forget to dump
>>> it in the debug patch, so could you apply the following new debug patch and
>>> provide us the log again? BTW, please attach the ftrace log in the reply
>>> mail directly, then it may be parsed/looked easily.
>>
>> I have resynced to the latest linux-next and applied your new patch.
>> The log is attached.
>>
>> Of note, it took several boots this time before it would progress to where I
>> could grab the log.
>> Instead it was blocking the moment RW was requested.
>> Also of note, it seems only the emmc is affected, the SD card (mmcblk2) does
>> not trigger any errors.
>
>>From the log you captured, seems there are three requests(33, 34, 60) blocked,
> which should have been inside mmc, but still need to confirm, could you apply the
> following one-line patch against the last debug patch and collect the log again?
>
> diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
> index d35f265cd5e0..ac2ffc5a8ed4 100644
> --- a/drivers/mmc/core/queue.c
> +++ b/drivers/mmc/core/queue.c
> @@ -321,6 +321,8 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
> !host->hold_retune;
> }
>
> + if (blk_queue_debug(q))
> + trace_printk("mmc before issue rq %d %d\n", req->internal_tag, req->tag);
> blk_mq_start_request(req);
>
> issued = mmc_blk_mq_issue_rq(mq, req);
>
>
> Also see comments in mmc_mq_queue_rq():
>
> /*
> * We use BLK_MQ_F_BLOCKING and have only 1 hardware queue, which means requests
> * will not be dispatched in parallel.
> */
>
> which isn't correct, given blk-mq has multiple sw queue and mmc sets the queue depth
> as > 1, and requests may be dispatched to the unique hw queue in parallel.
>
> Adrian, Ulf Hansson and anyone, could you take a look at the warning of WARN_ON(host->cmd)
> in sdhci_send_command()? Seems you only allow to queue one command, but not sure how you
> guarantee that.
We didn't guarantee it, but it didn't happen before "blk-mq: issue directly
if hw queue isn't busy in case of 'none'". We did consider adding a mutex, refer
https://lore.kernel.org/lkml/CAPDyKFr8tiJXSL-weQjGJ3DfRrfv8ZAFY8=ZECLNgSe_43S8Rw@xxxxxxxxxxxxxx/
However the following might do, do you think?
diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 648eb6743ed5..6edffeed9953 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -238,10 +238,6 @@ static void mmc_mq_exit_request(struct blk_mq_tag_set *set, struct request *req,
mmc_exit_request(mq->queue, req);
}
-/*
- * We use BLK_MQ_F_BLOCKING and have only 1 hardware queue, which means requests
- * will not be dispatched in parallel.
- */
static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
const struct blk_mq_queue_data *bd)
{
@@ -264,7 +260,7 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
spin_lock_irq(q->queue_lock);
- if (mq->recovery_needed) {
+ if (mq->recovery_needed || mq->busy) {
spin_unlock_irq(q->queue_lock);
return BLK_STS_RESOURCE;
}
@@ -291,6 +287,9 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
break;
}
+ /* Parallel dispatch of requests is not supported at the moment */
+ mq->busy = true;
+
mq->in_flight[issue_type] += 1;
get_card = (mmc_tot_in_flight(mq) == 1);
cqe_retune_ok = (mmc_cqe_qcnt(mq) == 1);
@@ -333,9 +332,12 @@ static blk_status_t mmc_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
mq->in_flight[issue_type] -= 1;
if (mmc_tot_in_flight(mq) == 0)
put_card = true;
+ mq->busy = false;
spin_unlock_irq(q->queue_lock);
if (put_card)
mmc_put_card(card, &mq->ctx);
+ } else {
+ WRITE_ONCE(mq->busy, false);
}
return ret;
diff --git a/drivers/mmc/core/queue.h b/drivers/mmc/core/queue.h
index 17e59d50b496..9bf3c9245075 100644
--- a/drivers/mmc/core/queue.h
+++ b/drivers/mmc/core/queue.h
@@ -81,6 +81,7 @@ struct mmc_queue {
unsigned int cqe_busy;
#define MMC_CQE_DCMD_BUSY BIT(0)
#define MMC_CQE_QUEUE_FULL BIT(1)
+ bool busy;
bool use_cqe;
bool recovery_needed;
bool in_recovery;
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