Re: [PATCH] ata: libata-scsi: Avoid deadlock on rescan after device resume

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

On 6/16/23 12:31, Kai-Heng Feng wrote:
> On Thu, Jun 15, 2023 at 4:33 PM Damien Le Moal <dlemoal@kernel.org> wrote:
>>
>> When an ATA port is resumed from sleep, the port is reset and a power
>> management request issued to libata EH to reset the port and rescanning
>> the device(s) attached to the port. Device rescanning is done by
>> scheduling an ata_scsi_dev_rescan() work, which will execute
>> scsi_rescan_device().
>>
>> However, scsi_rescan_device() takes the generic device lock, which is
>> also taken by dpm_resume() when the SCSI device is resumed as well. If
>> a device rescan execution starts before the completion of the SCSI
>> device resume, the rcu locking used to refresh the cached VPD pages of
>> the device, combined with the generic device locking from
>> scsi_rescan_device() and from dpm_resume() can cause a deadlock.
>>
>> Avoid this situation by changing struct ata_port scsi_rescan_task to be
>> a delayed work instead of a simple work_struct. ata_scsi_dev_rescan() is
>> modified to check if the SCSI device associated with the ATA device that
>> must be rescanned is not suspended. If the SCSI device is still
>> suspended, ata_scsi_dev_rescan() returns early and reschedule itself for
>> execution after an arbitrary delay of 5ms.
>>
>> Reported-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
>> Reported-by: Joe Breuer <linux-kernel@jmbreuer.net>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217530
>> Fixes: a19a93e4c6a9 ("scsi: core: pm: Rely on the device driver core for async power management")
>> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> 
> Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

Thanks !

Joe,

Did you have a chance to test ?

-- 
Damien Le Moal
Western Digital Research