@@ -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);
}
@@ -4760,7 +4760,7 @@ 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);
@@ -4769,37 +4769,34 @@ 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));
}
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> --- drivers/ata/libata-core.c | 16 ++++++++++++++++ drivers/ata/libata-scsi.c | 33 +++++++++++++++------------------ 2 files changed, 31 insertions(+), 18 deletions(-)