usb: gadget: pch_udc: reorder spin_[un]lock to avoid deadlock

The above commit reordered spin_lock/unlock and now `&dev->lock' is acquired
(rather than released) before calling `dev->driver->disconnect',
`dev->driver->setup', `dev->driver->suspend', `usb_gadget_giveback_request', and
`usb_gadget_udc_reset'.

But this *may* not be the right way to fix the problem pointed by d3cb25a12138.

Note that the other usb/gadget/udc drivers do release the lock before calling
these functions. There are also inconsistencies within pch_udc.c, where
`dev->driver->disconnect' is called while holding `&dev->lock' in lines 613 and
1184, but not in line 2739.

Finally, commit d3cb25a12138 may have introduced several potential deadlocks.

For instance, EBA (https://github.com/models-team/eba) reports:

    Double lock in drivers/usb/gadget/udc/pch_udc.c
    first at 2791: spin_lock(& dev->lock); [pch_udc_isr]
    second at 2694: spin_lock(& dev->lock); [pch_udc_svc_cfg_interrupt]
        after calling from 2793: pch_udc_dev_isr(dev, dev_intr);
        after calling from 2724: pch_udc_svc_cfg_interrupt(dev);

Similarly, other potential deadlocks are 2791 -> 2793 -> 2721 -> 2657; and
2791 -> 2793 -> 2711 -> 2573 -> 1499 -> 1480.

Fixes: d3cb25a12138 ("usb: gadget: udc: fix spin_lock in pch_udc")
Signed-off-by: Iago Abal <mail@iagoabal.eu>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

diff --git a/drivers/usb/gadget/udc/pch_udc.c b/drivers/usb/gadget/udc/pch_udc.c
index 8ad847a..a97da64 100644 (file)
--- a/drivers/usb/gadget/udc/pch_udc.c
+++ b/drivers/usb/gadget/udc/pch_udc.c
@@ -1477,11 +1477,11 @@ static void complete_req(struct pch_udc_ep *ep, struct pch_udc_request *req,
                req->dma_mapped = 0;
        }
        ep->halted = 1;
-       spin_lock(&dev->lock);
+       spin_unlock(&dev->lock);
        if (!ep->in)
                pch_udc_ep_clear_rrdy(ep);
        usb_gadget_giveback_request(&ep->ep, &req->req);
-       spin_unlock(&dev->lock);
+       spin_lock(&dev->lock);
        ep->halted = halted;
 }
 
@@ -2567,9 +2567,9 @@ static void pch_udc_svc_ur_interrupt(struct pch_udc_dev *dev)
                empty_req_queue(ep);
        }
        if (dev->driver) {
-               spin_lock(&dev->lock);
-               usb_gadget_udc_reset(&dev->gadget, dev->driver);
                spin_unlock(&dev->lock);
+               usb_gadget_udc_reset(&dev->gadget, dev->driver);
+               spin_lock(&dev->lock);
        }
 }
 
@@ -2648,9 +2648,9 @@ static void pch_udc_svc_intf_interrupt(struct pch_udc_dev *dev)
                dev->ep[i].halted = 0;
        }
        dev->stall = 0;
-       spin_lock(&dev->lock);
-       dev->driver->setup(&dev->gadget, &dev->setup_data);
        spin_unlock(&dev->lock);
+       dev->driver->setup(&dev->gadget, &dev->setup_data);
+       spin_lock(&dev->lock);
 }
 
 /**
@@ -2685,9 +2685,9 @@ static void pch_udc_svc_cfg_interrupt(struct pch_udc_dev *dev)
        dev->stall = 0;
 
        /* call gadget zero with setup data received */
-       spin_lock(&dev->lock);
-       dev->driver->setup(&dev->gadget, &dev->setup_data);
        spin_unlock(&dev->lock);
+       dev->driver->setup(&dev->gadget, &dev->setup_data);
+       spin_lock(&dev->lock);
 }
 
 /**