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ata: libata-scsi: Fix delayed scsi_rescan_device() execution

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Commit 6aa0365a3c85 ("ata: libata-scsi: Avoid deadlock on rescan after
device resume") modified ata_scsi_dev_rescan() to check the scsi device
"is_suspended" power field to ensure that the scsi device associated
with an ATA device is fully resumed when scsi_rescan_device() is
executed. However, this fix is problematic as:
1) It relies on a PM internal field that should not be used without PM
   device locking protection.
2) The check for is_suspended and the call to scsi_rescan_device() are
   not atomic and a suspend PM event may be triggered between them,
   casuing scsi_rescan_device() to be called on a suspended device and
   in that function blocking while holding the scsi device lock. This
   would deadlock a following resume operation.
These problems can trigger PM deadlocks on resume, especially with
resume operations triggered quickly after or during suspend operations.
E.g., a simple bash script like:

for (( i=0; i<10; i++ )); do
	echo "+2 > /sys/class/rtc/rtc0/wakealarm
	echo mem > /sys/power/state
done

that triggers a resume 2 seconds after starting suspending a system can
quickly lead to a PM deadlock preventing the system from correctly
resuming.

Fix this by replacing the check on is_suspended with a check on the
return value given by scsi_rescan_device() as that function will fail if
called against a suspended device. Also make sure rescan tasks already
scheduled are first cancelled before suspending an ata port.

Fixes: 6aa0365a3c85 ("ata: libata-scsi: Avoid deadlock on rescan after device resume")
Cc: stable@vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Niklas Cassel <niklas.cassel@wdc.com>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Damien Le Moal 2023-09-05 09:06:23 +09:00
parent ff48b37802
commit 8b4d9469d0
2 changed files with 31 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/ata/libata-core.c
View File

@ -5168,11 +5168,27 @@ static const unsigned int ata_port_suspend_ehi = ATA_EHI_QUIET
static void ata_port_suspend(struct ata_port *ap, pm_message_t mesg)
{
/*
* We are about to suspend the port, so we do not care about
* scsi_rescan_device() calls scheduled by previous resume operations.
* The next resume will schedule the rescan again. So cancel any rescan
* that is not done yet.
*/
cancel_delayed_work_sync(&ap->scsi_rescan_task);
ata_port_request_pm(ap, mesg, 0, ata_port_suspend_ehi, false);
}
static void ata_port_suspend_async(struct ata_port *ap, pm_message_t mesg)
{
/*
* We are about to suspend the port, so we do not care about
* scsi_rescan_device() calls scheduled by previous resume operations.
* The next resume will schedule the rescan again. So cancel any rescan
* that is not done yet.
*/
cancel_delayed_work_sync(&ap->scsi_rescan_task);
ata_port_request_pm(ap, mesg, 0, ata_port_suspend_ehi, true);
}

33
drivers/ata/libata-scsi.c
View File

@ -4756,7 +4756,7 @@ void ata_scsi_dev_rescan(struct work_struct *work)
struct ata_link *link;
struct ata_device *dev;
unsigned long flags;
bool delay_rescan = false;
int ret = 0;
mutex_lock(&ap->scsi_scan_mutex);
spin_lock_irqsave(ap->lock, flags);
@ -4765,37 +4765,34 @@ void ata_scsi_dev_rescan(struct work_struct *work)
ata_for_each_dev(dev, link, ENABLED) {
struct scsi_device *sdev = dev->sdev;
/*
* If the port was suspended before this was scheduled,
* bail out.
*/
if (ap->pflags & ATA_PFLAG_SUSPENDED)
goto unlock;
if (!sdev)
continue;
if (scsi_device_get(sdev))
continue;
/*
* If the rescan work was scheduled because of a resume
* event, the port is already fully resumed, but the
* SCSI device may not yet be fully resumed. In such
* case, executing scsi_rescan_device() may cause a
* deadlock with the PM code on device_lock(). Prevent
* this by giving up and retrying rescan after a short
* delay.
*/
delay_rescan = sdev->sdev_gendev.power.is_suspended;
if (delay_rescan) {
scsi_device_put(sdev);
break;
}
spin_unlock_irqrestore(ap->lock, flags);
scsi_rescan_device(sdev);
ret = scsi_rescan_device(sdev);
scsi_device_put(sdev);
spin_lock_irqsave(ap->lock, flags);
if (ret)
goto unlock;
}
}
unlock:
spin_unlock_irqrestore(ap->lock, flags);
mutex_unlock(&ap->scsi_scan_mutex);
if (delay_rescan)
/* Reschedule with a delay if scsi_rescan_device() returned an error */
if (ret)
schedule_delayed_work(&ap->scsi_rescan_task,
msecs_to_jiffies(5));
}