Re: [PATCH v4 09/23] scsi: sd: Do not issue commands to suspended disks on shutdown

[Damien Le Moal <dlemoal@kernel.org>]

On 2023/09/21 14:36, Bart Van Assche wrote:
> On 9/20/23 06:54, Damien Le Moal wrote:
>> If an error occurs when resuming a host adapter before the devices
>> attached to the adapter are resumed, the adapter low level driver may
>> remove the scsi host, resulting in a call to sd_remove() for the
>> disks of the host. This in turn results in a call to sd_shutdown() which
>> will issue a synchronize cache command and a start stop unit command to
>> spindown the disk. sd_shutdown() issues the commands only if the device
>> is not already suspended but does not check the power state for
>> system-wide suspend/resume. That is, the commands may be issued with the
>> device in a suspended state, which causes PM resume to hang, forcing a
>> reset of the machine to recover.
>>
>> Fix this by not calling sd_shutdown() in sd_remove() if the device
>> is not running.
> 
> Hi Damien,
> 
> I'd like to look into an alternative fix (after this patch series went 
> in) but I couldn't identify the call chain in the ATA resume code that 
> results in removal of the SCSI host. Can you please show me the call 
> chain that results in SCSI host removal if resuming fails?

See the pm80xx driver for which I recently fixed a resume issue. That is how I
found this problem with device removal: resuming the pm800xx HBA was failing and
the driver then called scsi_remove_host() to drop the ports and that led to
trying to removed sd devices that were still suspended.

> 
> Thanks,
> 
> Bart.
> 

-- 
Damien Le Moal
Western Digital Research