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

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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 d3cb25a121.

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 d3cb25a121 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: d3cb25a121 ("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>
This commit is contained in:
Iago Abal 2016-06-21 12:01:11 +02:00 committed by Felipe Balbi
parent 4320280001
commit 1d23d16a88
1 changed files with 8 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/usb/gadget/udc/pch_udc.c
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@ -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);
}
/**