linux-kernel - Deadlock in pch_udc_svc_ur

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Date:	Mon, 28 Sep 2015 16:12:33 +0400
From:	Alexey Khoroshilov <khoroshilov@...ras.ru>
To:	Felipe Balbi <balbi@...com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org
Subject: Deadlock in pch_udc_svc_ur_interrupt()

Dear colleagus,

It seems code handling USB_RESET interrupt contains unavoidable deadlock.

pch_udc_isr() locks dev->lock, then calls to pch_udc_dev_isr(dev, dev_intr)
that seems to have a couple of locks dev->lock itself:

pch_udc_isr()
  spin_lock(&dev->lock);
  pch_udc_dev_isr(dev, dev_intr);
    pch_udc_svc_ur_interrupt(dev);
      empty_req_queue(ep);
        complete_req(ep, req, -ESHUTDOWN);
          spin_lock(&dev->lock);                  <--- deadlock
      if (dev->driver) { spin_lock(&dev->lock); } <--- deadlock

Found by Linux Driver Verification project (linuxtesting.org).

--
Alexey Khoroshilov
Linux Verification Center, ISPRAS
web: http://linuxtesting.org

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