USB: keep count of unsuspended children

This patch (as818b) simplifies autosuspend processing by keeping track
of the number of unsuspended children of each USB hub.  This will
permit us to avoid a good deal of unnecessary work all the time; we
will no longer have to create a bunch of workqueue entries to carry
out autosuspend requests, only to have them fail because one of the
hub's children isn't suspended.

The basic idea is simple.  There already is a usage counter in the
usb_device structure for preventing autosuspends.  The patch just
increments that counter for every unsuspended child.  There's only one
tricky part: When a device disconnects we need to remember whether it
was suspended at the time (leave the counter alone) or not (decrement
the counter).

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

2 files changed, 37 insertions, 11 deletions

diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
index 40c1bf09b2b7..0fa15bd62c48 100644
--- a/drivers/usb/core/driver.c
+++ b/drivers/usb/core/driver.c
@@ -1048,7 +1048,7 @@ int usb_suspend_both(struct usb_device *udev, pm_message_t msg)
 
         /* If the suspend succeeded, propagate it up the tree */
         } else if (parent)
-                usb_autosuspend_device(parent, 0);
+                usb_autosuspend_device(parent, 1);
 
         // dev_dbg(&udev->dev, "%s: status %d\n", __FUNCTION__, status);
         return status;
@@ -1096,9 +1096,25 @@ int usb_resume_both(struct usb_device *udev)
         /* Propagate the resume up the tree, if necessary */
         if (udev->state == USB_STATE_SUSPENDED) {
                 if (parent) {
-                        usb_pm_lock(parent);
-                        parent->auto_pm = 1;
-                        status = usb_resume_both(parent);
+                        status = usb_autoresume_device(parent, 1);
+                        if (status == 0) {
+                                status = usb_resume_device(udev);
+                                if (status) {
+                                        usb_autosuspend_device(parent, 1);
+
+                                        /* It's possible usb_resume_device()
+                                         * failed after the port was
+                                         * unsuspended, causing udev to be
+                                         * logically disconnected.  We don't
+                                         * want usb_disconnect() to autosuspend
+                                         * the parent again, so tell it that
+                                         * udev disconnected while still
+                                         * suspended. */
+                                        if (udev->state ==
+                                                        USB_STATE_NOTATTACHED)
+                                                udev->discon_suspended = 1;
+                                }
+                        }
                 } else {
 
                         /* We can't progagate beyond the USB subsystem,
@@ -1107,11 +1123,9 @@ int usb_resume_both(struct usb_device *udev)
                         if (udev->dev.parent->power.power_state.event !=
                                         PM_EVENT_ON)
                                 status = -EHOSTUNREACH;
-                }
-                if (status == 0)
-                        status = usb_resume_device(udev);
-                if (parent)
-                        usb_pm_unlock(parent);
+                        else
+                                status = usb_resume_device(udev);
+                }
         } else {
 
                 /* Needed only for setting udev->dev.power.power_state.event
@@ -1119,8 +1133,6 @@ int usb_resume_both(struct usb_device *udev)
                 status = usb_resume_device(udev);
         }
 
-        /* Now the parent won't suspend until we are finished */
-
         if (status == 0 && udev->actconfig) {
                 for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
                         intf = udev->actconfig->interface[i];
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 46df5e60764b..e46d38b18249 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1039,6 +1039,8 @@ static void recursively_mark_NOTATTACHED(struct usb_device *udev)
                 if (udev->children[i])
                         recursively_mark_NOTATTACHED(udev->children[i]);
         }
+        if (udev->state == USB_STATE_SUSPENDED)
+                udev->discon_suspended = 1;
         udev->state = USB_STATE_NOTATTACHED;
 }
 
@@ -1228,6 +1230,14 @@ void usb_disconnect(struct usb_device **pdev)
         *pdev = NULL;
         spin_unlock_irq(&device_state_lock);
 
+        /* Decrement the parent's count of unsuspended children */
+        if (udev->parent) {
+                usb_pm_lock(udev);
+                if (!udev->discon_suspended)
+                        usb_autosuspend_device(udev->parent, 1);
+                usb_pm_unlock(udev);
+        }
+
         put_device(&udev->dev);
 }
 
@@ -1356,6 +1366,10 @@ static int __usb_new_device(void *void_data)
                 goto fail;
         }
 
+        /* Increment the parent's count of unsuspended children */
+        if (udev->parent)
+                usb_autoresume_device(udev->parent, 1);
+
 exit:
         module_put(THIS_MODULE);
         return err;