On Thu, 10 Apr 2014, David Laight wrote:

> You also definitely don't want to cancel an isoc urb.
> Doing so is likely to corrupt the kernel heap.
> 
> If an isoc urb generates multiple TRB the code allocates a little
> structure 'per TRB' and links it to the urb.
> This seems to be done so that it can tell when all the TRB have
> finished so that it can complete the urb.
> However if a transfer is aborted they get freed individually, but
> they were allocated as a single item.
> I actually suspect the driver doesn't care about the early TRB,
> so shouldn't need the list at all.

You've got it backward: We _do_ want to cancel isochronous URBs 
sometimes.  If doing so will corrupt the kernel heap then the driver 
needs to be fixed.

Alan Stern

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