Re: [Regression] Linux-Next Merge 25Jul2018 breaks mmc on Tegra.

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:

quoted

On 07/28/2018 09:37 AM, Ming Lei wrote:

...

quoted

[   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"

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.