linux-kernel - Re: [PATCH] mmc: block: Prevent new req entering queue while freeing up the queue

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Date:   Wed, 11 Nov 2020 21:52:35 +0530
From:   Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Adrian Hunter <adrian.hunter@...el.com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>,
        Baolin Wang <baolin.wang@...aro.org>,
        Chaotian Jing <chaotian.jing@...iatek.com>,
        Peng Hao <richard.peng@...o.com>
Subject: Re: [PATCH] mmc: block: Prevent new req entering queue while freeing
 up the queue


On 11/3/2020 8:55 PM, Ulf Hansson wrote:
> On Wed, 28 Oct 2020 at 12:20, Veerabhadrarao Badiganti
> <vbadigan@...eaurora.org> wrote:
>> The commit bbdc74dc19e0 ("mmc: block: Prevent new req entering queue
>> after its cleanup") has introduced this change but it got moved after
>> del_gendisk() with commit 57678e5a3d51 ("mmc: block: Delete gendisk
>> before cleaning up the request queue").
> This isn't the first time we have spotted errors in this path. Seems
> like a difficult path to get correct. :-)
>
>> It is blocking reboot with below Call stack().
>>
>> INFO: task reboot:3086 blocked for more than 122 seconds.
>>       __schedule
>>       schedule
>>       schedule_timeout
>>       io_schedule_timeout
>>       do_wait_for_common
>>       wait_for_completion_io
>>       submit_bio_wait
>>       blkdev_issue_flush
>>       ext4_sync_fs
>>       __sync_filesystem
>>       sync_filesystem
>>       fsync_bdev
>>       invalidate_partition
>>       del_gendisk
>>       mmc_blk_remove_req
>>       mmc_blk_remove
>>       mmc_bus_remove
>>       device_release_driver_internal
>>       device_release_driver
>>       bus_remove_device
>>       device_del
>>       mmc_remove_card
>>       mmc_remove
>>       mmc_stop_host
>>       mmc_remove_host
>>       sdhci_remove_host
>>       sdhci_msm_remove
> Why do you call sdhci_msm_remove() from the shutdown callback? What
> specific operations do you need to run in the shutdown path for sdhci
> msm?
I was suggested to add shutdown callback by memory team to gracefully 
de-register with smmu driver
during reboot/shutdown. So tried adding it. Since SMMU team.

I just need to ensure that controller is not active anymore and not 
accessing memory related to any
requests and de-register with smmu driver during shutdown.
>
> The important part should be to do a graceful shutdown of the card
> (and the block device) - is there anything else?
>
> Or you are just using the shutdown callback as a simple way to trigger
> this problem? Could unbinding the driver trigger the same issue?
>
>>       sdhci_msm_shutdown
>>       platform_drv_shutdown
>>       device_shutdown
>>       kernel_restart_prepare
>>       kernel_restart
>>
>> So bringing this change back.
>>
>> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@...eaurora.org>
>> ---
>>
>> I'm observing this issue 100% of the time with shutdown callback added to sdhci-msm driver.
>> I'm trying on 5.4 kernel with ChromeOS.
>>
>> Please let me know if this can be fixed in a better way.
> I don't know yet, but I will have a closer look. Let's also see if
> Adrian has some thoughts.
>
> Kind regards
> Uffe
>
>> ---
>>
>>   drivers/mmc/core/block.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
>> index 8d3df0be0355..76dbb2b8a13b 100644
>> --- a/drivers/mmc/core/block.c
>> +++ b/drivers/mmc/core/block.c
>> @@ -2627,6 +2627,7 @@ static void mmc_blk_remove_req(struct mmc_blk_data *md)
>>                   * from being accepted.
>>                   */
>>                  card = md->queue.card;
>> +               blk_set_queue_dying(md->queue.queue);
>>                  if (md->disk->flags & GENHD_FL_UP) {
>>                          device_remove_file(disk_to_dev(md->disk), &md->force_ro);
>>                          if ((md->area_type & MMC_BLK_DATA_AREA_BOOT) &&
>> --
>> Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc., is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
>>