[linux-dvb] [BUG] changeset 9029 (http://linuxtv.org/hg/v4l-dvb/rev/aa3e5cc1d833)

Oliver Endriss o.endriss at gmx.de
Wed Feb 18 17:47:07 CET 2009


Trent Piepho wrote:
> On Wed, 18 Feb 2009, Oliver Endriss wrote:
> > [1] If you want to lock a process against an interrupt handler,
> > - the process must use spin_lock_irq()
> > - the interrupt can use spin_lock()
> >
> > A routine has to use spin_lock_irqsave if (and only if) process and irq
> > call the routine concurrently. I do not see yet how this might happen.
> 
> Some code calls the swfilter functions from process context and some
> drivers call them from interrupt context.

There would be a problem if (and only if) it could happen concurrently
within a given driver. A driver may call the functions either from
process context or from a tasklet/irq.

User space access will occur only if demux_source == DMX_MEMORY_FE.
In this case the driver must not call the routine.

If demux_source == DMX_FRONTEND, the driver may call the routine,
but userspace won't.

Sorry, I need more information to identify the problem.

CU
Oliver

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