On Mon, Apr 15, 2024 at 10:47 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > Actually, I've got a completely different patch which I think will fix > the problem you encountered. Instead of using mutual exclusion to > avoid the race, it prevents the two routines from being called at the > same time so the race can't occur in the first place. It also should > guarantee the usb_hub_to_struct_hub() doesn't return NULL when > disable_store() calls it. > > Can you try the patch below, instead of (not along with) the first > patch? Thanks. > > Alan Stern > > > > Index: usb-devel/drivers/usb/core/hub.c > =================================================================== > --- usb-devel.orig/drivers/usb/core/hub.c > +++ usb-devel/drivers/usb/core/hub.c > @@ -1788,16 +1788,15 @@ static void hub_disconnect(struct usb_in > > mutex_lock(&usb_port_peer_mutex); > > + for (port1 = hdev->maxchild; port1 > 0; --port1) > + usb_hub_remove_port_device(hub, port1); > + > /* Avoid races with recursively_mark_NOTATTACHED() */ > spin_lock_irq(&device_state_lock); > - port1 = hdev->maxchild; > hdev->maxchild = 0; > usb_set_intfdata(intf, NULL); > spin_unlock_irq(&device_state_lock); > > - for (; port1 > 0; --port1) > - usb_hub_remove_port_device(hub, port1); > - > mutex_unlock(&usb_port_peer_mutex); > > if (hub->hdev->speed == USB_SPEED_HIGH) > I tried this patch and it worked. I agree this patch is better and it avoids introducing new locks. Best, Yue
