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 726fa072c3fe3ddc1566f7b8ef0a3d4fa32714bc..5f43c22ba787971e07ac9fe7ef09b91ea5e95ed5 100644 (file)
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1276,12 +1276,22 @@ static void hub_quiesce(struct usb_hub *hub, enum hub_quiescing_type type)
                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 @@ static int hub_post_reset(struct usb_interface *intf)
 {
        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;
 }

diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 33bcb2c6f90a025214afe072bf82c632ac6d4e8e..f9b521e601282afbe6091b49178547757e47c727 100644 (file)
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -66,6 +66,7 @@ struct usb_hub {
        unsigned                limited_power:1;
        unsigned                quiescing:1;
        unsigned                disconnected:1;
+       unsigned                in_reset:1;
 
        unsigned                quirk_check_port_auto_suspend:1;
 

diff --git a/drivers/usb/core/port.c b/drivers/usb/core/port.c
index 51542f852393b0cca35844daafc3cb5f8283c9ba..37647e080599b951c9c29bb141a9eae33fd56e70 100644 (file)
--- a/drivers/usb/core/port.c
+++ b/drivers/usb/core/port.c
@@ -81,6 +81,10 @@ static int usb_port_runtime_resume(struct device *dev)
 
        if (!hub)
                return -EINVAL;
+       if (hub->in_reset) {
+               port_dev->power_is_on = 1;
+               return 0;
+       }
 
        usb_autopm_get_interface(intf);
        set_bit(port1, hub->busy_bits);
@@ -117,6 +121,8 @@ static int usb_port_runtime_suspend(struct device *dev)
 
        if (!hub)
                return -EINVAL;
+       if (hub->in_reset)
+               return -EBUSY;
 
        if (dev_pm_qos_flags(&port_dev->dev, PM_QOS_FLAG_NO_POWER_OFF)
                        == PM_QOS_FLAGS_ALL)