6.5-stable review patch. If anyone has any objections, please let me know.
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From: Damien Le Moal dlemoal@kernel.org
[ Upstream commit 8b4d9469d0b0e553208ee6f62f2807111fde18b9 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/ata/libata-core.c | 16 ++++++++++++++++ drivers/ata/libata-scsi.c | 33 +++++++++++++++------------------ 2 files changed, 31 insertions(+), 18 deletions(-)
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 76bf185a73c65..6ae9cff6b50c5 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -5245,11 +5245,27 @@ 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); }
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c index 22d7c26297889..ed3146c460910 100644 --- a/drivers/ata/libata-scsi.c +++ b/drivers/ata/libata-scsi.c @@ -4900,7 +4900,7 @@ 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); @@ -4909,37 +4909,34 @@ 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)); }