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

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On 11/3/2020 8:55 PM, Ulf Hansson wrote:
On Wed, 28 Oct 2020 at 12:20, Veerabhadrarao Badiganti
<vbadigan@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
---

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




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