Please consider som rewrite:
On 17/11/2021 02:45, chenxiang wrote:
"scsi: libsas: Keep sas host active until finished some work" -> "scsi:
libsas: Keep host active while processing events"
From: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
For those works from event queue, if executing them such as
PORTE_BROADCAST_RCVD when sas host is suspended, it will resume sas host
firstly as SMP IOs are sent in the process. So phyup will occur and it
will call work PORTE_BYTES_DMAED. But the original work (such as
PORTE_BROADCAST_RCVD) and the work PORTE_BYTES_DMAED are in the same
singlethread workqueue, so the complete of original work waits for
the complete of work PORTE_BYTES_DMAED while the complete of work
PORTE_BYTES_DMAED wait for the complete of original and it is blocked.
So call pm_runtime_get_noresume() to keep sas host active until
finished those works.
Processing events such as PORTE_BROADCAST_RCVD may cause dependency
issues for runtime power management support.
Such a problem would be that handling a PORTE_BROADCAST_RCVD event
requires that the host is resumed to send SMP commands. However, in
resuming the host, the phyup events generated from re-enabling the phys
are processed in the same workqueue as the original PORTE_BROADCAST_RCVD
event. As such, the host will never finish resuming (as it waits for the
phyup event processing), and then the PORTE_BROADCAST_RCVD event cannot
be processed as the SMP commands are blocked, and so we have a deadlock.
Solve this problem by ensuring that libsas keeps the host active until
completely finished processing phy or port events, such as
PORTE_BYTES_DMAED. As such, we don't have to worry about resuming the
host for processing individual SMP commands in this example.
Signed-off-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
Reviewed-by: John Garry <john.garry@xxxxxxxxxx>
---
drivers/scsi/libsas/sas_event.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/drivers/scsi/libsas/sas_event.c b/drivers/scsi/libsas/sas_event.c
index 626ef96b9348..3613b9b315bc 100644
--- a/drivers/scsi/libsas/sas_event.c
+++ b/drivers/scsi/libsas/sas_event.c
@@ -50,8 +50,10 @@ void sas_queue_deferred_work(struct sas_ha_struct *ha)
list_for_each_entry_safe(sw, _sw, &ha->defer_q, drain_node) {
list_del_init(&sw->drain_node);
ret = sas_queue_work(ha, sw);
- if (ret != 1)
+ if (ret != 1) {
+ pm_runtime_put(ha->dev);
sas_free_event(to_asd_sas_event(&sw->work));
+ }
}
spin_unlock_irq(&ha->lock);
}
@@ -126,16 +128,22 @@ void sas_enable_revalidation(struct sas_ha_struct *ha)
static void sas_port_event_worker(struct work_struct *work)
{
struct asd_sas_event *ev = to_asd_sas_event(work);
+ struct asd_sas_phy *phy = ev->phy;
+ struct sas_ha_struct *ha = phy->ha;
sas_port_event_fns[ev->event](work);
+ pm_runtime_put(ha->dev);
sas_free_event(ev);
}
static void sas_phy_event_worker(struct work_struct *work)
{
struct asd_sas_event *ev = to_asd_sas_event(work);
+ struct asd_sas_phy *phy = ev->phy;
+ struct sas_ha_struct *ha = phy->ha;
sas_phy_event_fns[ev->event](work);
+ pm_runtime_put(ha->dev);
sas_free_event(ev);
}
@@ -170,14 +178,19 @@ int sas_notify_port_event(struct asd_sas_phy *phy, enum port_event event,
if (!ev)
return -ENOMEM;
+ /* Call pm_runtime_put() with pairs in sas_port_event_worker() */
+ pm_runtime_get_noresume(ha->dev);
+
INIT_SAS_EVENT(ev, sas_port_event_worker, phy, event);
if (sas_defer_event(phy, ev))
return 0;
ret = sas_queue_event(event, &ev->work, ha);
- if (ret != 1)
+ if (ret != 1) {
+ pm_runtime_put(ha->dev);
sas_free_event(ev);
+ }
return ret;
}
@@ -196,14 +209,19 @@ int sas_notify_phy_event(struct asd_sas_phy *phy, enum phy_event event,
if (!ev)
return -ENOMEM;
+ /* Call pm_runtime_put() with pairs in sas_phy_event_worker() */
+ pm_runtime_get_noresume(ha->dev);
+
INIT_SAS_EVENT(ev, sas_phy_event_worker, phy, event);
if (sas_defer_event(phy, ev))
return 0;
ret = sas_queue_event(event, &ev->work, ha);
- if (ret != 1)
+ if (ret != 1) {
+ pm_runtime_put(ha->dev);
sas_free_event(ev);
+ }
return ret;
}
