21285 serial driver deadlock(?) fix

[Steve M]

I was worried about the regular UART ops wanting a synced version, so I made
a nonsynced version specifically to be called from the interrupt handler. I
am attaching that patch for reference.

On Mon, Jan 11, 2010 at 12:57 PM, Simon Kagstrom <
simon.kagstrom at netinsight.net> wrote:

> (Added the list to To: as well)
>
> On Tue, 5 Jan 2010 21:37:42 +0300
> Steve M <stevenm86 at gmail.com> wrote:
>
> > I know little of the serial layer, but I am not certain that it is a good
> > idea to put _nosync directly into the stop_tx function, since this is a
> > function whose pointer is given out to the upper layer. We may only want
> the
> > nosync behavior from within the ISR, but waiting for the ISR to complete
> in
> > other cases may be more appropriate.
>
> Well, I think serial21285_stop_tx also needs _nosync since it too is
> called from an interrupt handler:
>
>  static irqreturn_t serial21285_tx_chars(int irq, void *dev_id)
>  {
>        [...]
>        if (uart_circ_empty(xmit))
>                serial21285_stop_tx(port);
>  }
>
> Of course, we could make an unsynced version of the stop_tx/stop_rx
> which is called from the local interrupt handlers, and a synchronous
> one which gets called from the structure.
>
>
> I don't know if the function pointers in uart_ops would run into some
> problem with the _nosync versions? I haven't seen any problems during
> my tests here with them at least.
>
> // Simon
>
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