[PATCH] scsi: libsas: Fix SMP IO deadlock during HA resume

[Xingui Yang]

During sas_resume_ha() -> sas_drain_work(), ATA EH will trigger SMP IOs via
sas_phy_reset() -> sas_smp_phy_control() for expander-attached ATA devices.
Since ha->dev is RPM_RESUMING at that point, pm_runtime_get_sync() blocks
waiting for the resume to finish, but the resume is blocked in
sas_drain_work() waiting for the SMP IO — a deadlock.

Skip the PM get/put when SAS_HA_RESUMING is set. The hardware is already
initialized by the LLDD resume callback before sas_resume_ha() runs, so no
explicit resume is needed.

Only hisi_sas enables runtime PM among libsas LLDDs, so other drivers
(pm8001, isci, aic94xx, mvsas) are unaffected.

Fixes: 0da7ca4c4fd9 ("scsi: libsas: Resume host while sending SMP I/Os")
Signed-off-by: Xingui Yang <yangxingui@xxxxxxxxxx>
---
 drivers/scsi/libsas/sas_expander.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
index 811c9eb4fef1..77ae2ae7b2c4 100644
--- a/drivers/scsi/libsas/sas_expander.c
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -61,8 +61,17 @@ static int smp_execute_task_sg(struct domain_device *dev,
 	struct sas_internal *i =
 		to_sas_internal(dev->port->ha->shost->transportt);
 	struct sas_ha_struct *ha = dev->port->ha;
-
-	pm_runtime_get_sync(ha->dev);
+	bool skip_pm = test_bit(SAS_HA_RESUMING, &ha->state);
+
+	/*
+	 * Skip PM get/put during HA resume to avoid deadlock: the host is
+	 * RPM_RESUMING and the drain waits for this SMP IO to finish, but
+	 * pm_runtime_get_sync() would block on RPM_RESUMING. Safe because
+	 * hardware is already initialized by the LLDD before call
+	 * sas_resume_ha().
+	 */
+	if (!skip_pm)
+		pm_runtime_get_sync(ha->dev);
 	mutex_lock(&dev->ex_dev.cmd_mutex);
 	for (retry = 0; retry < 3; retry++) {
 		if (test_bit(SAS_DEV_GONE, &dev->state)) {
@@ -135,7 +144,8 @@ static int smp_execute_task_sg(struct domain_device *dev,
 		}
 	}
 	mutex_unlock(&dev->ex_dev.cmd_mutex);
-	pm_runtime_put_sync(ha->dev);
+	if (!skip_pm)
+		pm_runtime_put_sync(ha->dev);
 
 	BUG_ON(retry == 3 && task != NULL);
 	sas_free_task(task);
-- 
2.43.0