Re: [PATCH] tty: serial: fsl_lpuart: fix del_timer_sync() vs timer routine deadlock

[Bhuvanchandra DV]

On 12/03/2016 02:25 PM, Nikita Yushchenko wrote:

> 03.12.2016 10:06, Bhuvanchandra DV ÐÐÑÐÑ:
> > On 12/03/2016 02:58 AM, Nikita Yushchenko wrote:
> >
> > > > > Problem found via lockdep:
> > > > >
> > > > > - lpuart_set_termios() calls del_timer_sync(&sport->lpuart_timer) while
> > > > >     holding sport->port.lock
> > > > >
> > > > > - sport->lpuart_timer routine is lpuart_timer_func() that calls
> > > > >     lpuart_copy_rx_to_tty() that acquires same lock.
> > > > >
> > > > > To fix, move Rx DMA stopping out of lock, as it already is in other
> > > > > places
> > > > > in the same file.
> > > > >
> > > > > While at it, also make Rx DMA start/stop code to look the same is in
> > > > > other places in the same file.
> > > > Yeah I saw that too, never really came around to look closer into it.
> > > >
> > > > Thanks for looking into it.
> > > >
> > > > You removed the check whether there was an old configuration, I think
> > > > the idea of that was that we only resize DMA if it was configured
> > > > differently before...
> > > Per my code reading, checking for sport->lpuart_dma_rx_use should be
> > > enough, this flag will be set only if DMA was previously enabled,
> > The check is to make sure the reconfiguration of DMA is done only when
> > the baudrate is altered.
> Then, ok to use
>
> if (old && sport->lpuart_dma_rx_use) {...}
>
> in both places?

Looks ok to me.

--
Bhuvan