Re: [PATCH] mpx5200_uart: drop port lock across tty_flip_buffer() call

["Grant Likely" <grant.likely@secretlab.ca>]

On 7/25/07, Thomas Gleixner <tglx@linutronix.de> wrote:
> On Wed, 2007-07-25 at 13:42 -0600, Grant Likely wrote:
> > On 7/25/07, Thomas Gleixner <tglx@linutronix.de> wrote:
> > > The port lock needs to be dropped across the tty_flip_buffer call, as it
> > > would lead to a deadlock with the spin_lock(&port->lock) in uart_start()
> > >
> > > Uncovered by lockdep / preempt-rt
> > >
> > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> >
> > Instead of dropping the lock and reclaiming it, would it be better for
> > me to rework the driver to only grab the lock in the 'meat' of
> > mpc52xx_uart_int_rx_chars() and mpc52xx_uart_int_tx_chars()?   (As
> > opposed to holding the lock for the entirety of mpc52xx_uart_int())
>
> No, it's not worth the trouble. You need to protect the hardware access.
>
> > What convention is used in other drivers?
>
> The same.

Okay, thanks.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

Kumar, this is a bug fix, can you pick it up please?

-- 
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
grant.likely@secretlab.ca
(403) 399-0195