USB: mutual exclusion for resetting a hub and power-managing a port
The USB core doesn't properly handle mutual exclusion between
resetting a hub and changing the power states of the hub's ports. We
need to avoid sending port-power requests to the hub while it is being
reset, because such requests cannot succeed.
This patch fixes the problem by keeping track of when a reset is in
progress. At such times, attempts to suspend (power-off) a port will
fail immediately with -EBUSY, and calls to usb_port_runtime_resume()
will update the power_is_on flag and return immediately. When the
reset is complete, hub_activate() will automatically restore each port
to the proper power state.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 726fa07..5f43c22 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1276,12 +1276,22 @@
flush_work(&hub->tt.clear_work);
}
+static void hub_pm_barrier_for_all_ports(struct usb_hub *hub)
+{
+ int i;
+
+ for (i = 0; i < hub->hdev->maxchild; ++i)
+ pm_runtime_barrier(&hub->ports[i]->dev);
+}
+
/* caller has locked the hub device */
static int hub_pre_reset(struct usb_interface *intf)
{
struct usb_hub *hub = usb_get_intfdata(intf);
hub_quiesce(hub, HUB_PRE_RESET);
+ hub->in_reset = 1;
+ hub_pm_barrier_for_all_ports(hub);
return 0;
}
@@ -1290,6 +1300,8 @@
{
struct usb_hub *hub = usb_get_intfdata(intf);
+ hub->in_reset = 0;
+ hub_pm_barrier_for_all_ports(hub);
hub_activate(hub, HUB_POST_RESET);
return 0;
}