On 17.04.2018 10:07, Felipe Balbi wrote:
Hi,
Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx> writes:
On 16.04.2018 15:29, Felipe Balbi wrote:
Instead of allocating urb priv and, maybe, bail out due to xhci being
in DYING state, we can move the check earlier and avoid the memory
allocation altogether.
This also moves checking for DYING outside the lock.
Most cases set DYING with lock held, so if we first get the lock before
checking DYING we have a better chance of not being in the process of dying.
pretty sure that's atomic, though.
That's not what I'm after, your fix is cleaning up code in the case where DYING flag is
set before xhci_urb_enqueue() is called. I'm worried about the case when setting DYING flag races
with xhci_urb_enqueue(). i.e. xhci_urb_enqueue() is spinning on the lock, waiting, while
some other part of the driver is desperately trying to access hw with lock held, failing,
finally setting DYING flag, and then releasing lock.
If the check is done before taking the lock then the URB might be queued on dying device,
at a time when xhci_hc_died already started cancelling and giving back all queued URB
Small thing, but so is this cleanup, so not sure its worth the change
Look at the result. With this change we don't need to take a lock,
allocate memory, search for endpoint index, search for endpoint
state. All of those are needed for proper operation of the function, but
if the controller has already died, there's no point in going any
further.
But we might miss the fact that host died, and go even further, adding URB to list,
writing TRBs to ringbuffers etc.
In code we save one line,
goto: free_priv
-Mathias
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