The patch below does not apply to the 6.5-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.5.y
git checkout FETCH_HEAD
git cherry-pick -x 8b4d9469d0b0e553208ee6f62f2807111fde18b9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2023100443-freewill-shanty-0f05@gregkh' --subject-prefix 'PATCH 6.5.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 8b4d9469d0b0e553208ee6f62f2807111fde18b9 Mon Sep 17 00:00:00 2001
From: Damien Le Moal <dlemoal(a)kernel.org>
Date: Tue, 5 Sep 2023 09:06:23 +0900
Subject: [PATCH] ata: libata-scsi: Fix delayed scsi_rescan_device() execution
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(a)vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal(a)kernel.org>
Reviewed-by: Hannes Reinecke <hare(a)suse.de>
Reviewed-by: Niklas Cassel <niklas.cassel(a)wdc.com>
Tested-by: Geert Uytterhoeven <geert+renesas(a)glider.be>
Reviewed-by: Martin K. Petersen <martin.petersen(a)oracle.com>
diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
index a0bc01606b30..092372334e92 100644
--- a/drivers/ata/libata-core.c
+++ b/drivers/ata/libata-core.c
@@ -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);
}
diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
index a0e58d22d222..6850cac803c1 100644
--- a/drivers/ata/libata-scsi.c
+++ b/drivers/ata/libata-scsi.c
@@ -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));
}
The patch below does not apply to the 6.5-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.5.y
git checkout FETCH_HEAD
git cherry-pick -x ff48b37802e5c134e2dfc4d091f10b2eb5065a72
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2023100454-hamper-falsify-595d@gregkh' --subject-prefix 'PATCH 6.5.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From ff48b37802e5c134e2dfc4d091f10b2eb5065a72 Mon Sep 17 00:00:00 2001
From: Damien Le Moal <dlemoal(a)kernel.org>
Date: Fri, 15 Sep 2023 15:00:13 +0900
Subject: [PATCH] scsi: Do not attempt to rescan suspended devices
scsi_rescan_device() takes a scsi device lock before executing a device
handler and device driver rescan methods. Waiting for the completion of
any command issued to the device by these methods will thus be done with
the device lock held. As a result, there is a risk of deadlocking within
the power management code if scsi_rescan_device() is called to handle a
device resume with the associated scsi device not yet resumed.
Avoid such situation by checking that the target scsi device is in the
running state, that is, fully capable of executing commands, before
proceeding with the rescan and bailout returning -EWOULDBLOCK otherwise.
With this error return, the caller can retry rescaning the device after
a delay.
The state check is done with the device lock held and is thus safe
against incoming suspend power management operations.
Fixes: 6aa0365a3c85 ("ata: libata-scsi: Avoid deadlock on rescan after device resume")
Cc: stable(a)vger.kernel.org
Signed-off-by: Damien Le Moal <dlemoal(a)kernel.org>
Reviewed-by: Hannes Reinecke <hare(a)suse.de>
Reviewed-by: Niklas Cassel <niklas.cassel(a)wdc.com>
Tested-by: Geert Uytterhoeven <geert+renesas(a)glider.be>
Reviewed-by: Martin K. Petersen <martin.petersen(a)oracle.com>
Reviewed-by: Bart Van Assche <bvanassche(a)acm.org>
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 52014b2d39e1..3db4d31a03a1 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -1619,12 +1619,24 @@ int scsi_add_device(struct Scsi_Host *host, uint channel,
}
EXPORT_SYMBOL(scsi_add_device);
-void scsi_rescan_device(struct scsi_device *sdev)
+int scsi_rescan_device(struct scsi_device *sdev)
{
struct device *dev = &sdev->sdev_gendev;
+ int ret = 0;
device_lock(dev);
+ /*
+ * Bail out if the device is not running. Otherwise, the rescan may
+ * block waiting for commands to be executed, with us holding the
+ * device lock. This can result in a potential deadlock in the power
+ * management core code when system resume is on-going.
+ */
+ if (sdev->sdev_state != SDEV_RUNNING) {
+ ret = -EWOULDBLOCK;
+ goto unlock;
+ }
+
scsi_attach_vpd(sdev);
scsi_cdl_check(sdev);
@@ -1638,7 +1650,11 @@ void scsi_rescan_device(struct scsi_device *sdev)
drv->rescan(dev);
module_put(dev->driver->owner);
}
+
+unlock:
device_unlock(dev);
+
+ return ret;
}
EXPORT_SYMBOL(scsi_rescan_device);
diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h
index 49f768d0ff37..4c2dc8150c6d 100644
--- a/include/scsi/scsi_host.h
+++ b/include/scsi/scsi_host.h
@@ -764,7 +764,7 @@ scsi_template_proc_dir(const struct scsi_host_template *sht);
#define scsi_template_proc_dir(sht) NULL
#endif
extern void scsi_scan_host(struct Scsi_Host *);
-extern void scsi_rescan_device(struct scsi_device *);
+extern int scsi_rescan_device(struct scsi_device *sdev);
extern void scsi_remove_host(struct Scsi_Host *);
extern struct Scsi_Host *scsi_host_get(struct Scsi_Host *);
extern int scsi_host_busy(struct Scsi_Host *shost);