linux-kernel - Re: [PATCH v2 2/2] scsi: sd: Rework asynchronous resume support

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Message-ID: <d0a3007a-930f-4ae3-2830-ee35585e01d7@suse.de>
Date:   Thu, 21 Jul 2022 07:40:24 +0200
From:   Hannes Reinecke <hare@...e.de>
To:     Bart Van Assche <bvanassche@....org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     "Martin K . Petersen" <martin.petersen@...cle.com>,
        Jaegeuk Kim <jaegeuk@...nel.org>,
        scsi <linux-scsi@...r.kernel.org>,
        Ming Lei <ming.lei@...hat.com>,
        John Garry <john.garry@...wei.com>, ericspero@...oud.com,
        jason600.groome@...il.com,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] scsi: sd: Rework asynchronous resume support

On 7/20/22 18:51, Bart Van Assche wrote:
> On 7/20/22 00:47, Geert Uytterhoeven wrote:
>> With more debug options enabled, it prints:
>>
>> INFO: task kworker/0:7:283 blocked for more than 120 seconds.
>>        Not tainted 5.19.0-rc7-salvator-x-00794-g6780eb02b605 #1287
>> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
>> task:kworker/0:7     state:D stack:    0 pid:  283 ppid:     2 
>> flags:0x00000008
>> Workqueue: events ata_scsi_dev_rescan
>> Call trace:
>>   __switch_to+0xbc/0x124
>>   __schedule+0x540/0x71c
>>   schedule+0x58/0xa0
>>   io_schedule+0x18/0x34
>>   blk_mq_get_tag+0x138/0x244
>>   __blk_mq_alloc_requests+0x130/0x2f0
>>   blk_mq_alloc_request+0x74/0xa8
>>   scsi_alloc_request+0x10/0x30
>>   __scsi_execute+0x5c/0x18c
>>   scsi_vpd_inquiry+0x7c/0xdc
>>   scsi_get_vpd_size+0x34/0xa8
>>   scsi_get_vpd_buf+0x28/0xf4
>>   scsi_attach_vpd+0x44/0x170
>>   scsi_rescan_device+0x30/0x98
>>   ata_scsi_dev_rescan+0xc8/0xfc
>>   process_one_work+0x2e0/0x474
>>   worker_thread+0x1cc/0x270
>>   kthread+0xd8/0xe8
>>   ret_from_fork+0x10/0x20
>>
>> This doesn't look like it's blocked in the R-Car SATA driver, but on
>> some I/O scheduling event in the block core?
> 
> I'm not familiar with the SATA code but from a quick look it seems like 
> the above code is only triggered from inside the ATA error handler 
> (ata_do_eh() -> ata_eh_recover() -> ata_eh_revalidate_and_attach() -> 
> schedule_work(&(ap->scsi_rescan_task) -> ata_scsi_dev_rescan()). It 
> doesn't seem normal to me that the ATA error handler gets invoked during 
> a resume. How about testing the following two code changes?

Sadly, that _is_ the normal workflow. SATA EH gets invoked regularly, 
and is handling the device resets after resume.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
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