Re: Serial driver hangs
From: Paul Fulghum (paulkf_at_microgate.com)
Date: 09/30/04
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To: Alan Cox <alan@lxorguk.ukuu.org.uk> Date: Thu, 30 Sep 2004 16:25:04 -0500
On Thu, 2004-09-30 at 15:10, Alan Cox wrote:
> On Iau, 2004-09-30 at 21:30, Paul Fulghum wrote:
> > tty->flip.work.func and tty->flip.tqueue.routine
> > are set to flush_to_ldisc()
>
> flush_to_ldisc was ok, then someone added the low latency
> flag. In the current 2.6.9rc3 patch flush_to_ldisc honours
> TTY_DONT_FLIP also
In the cases I described the low latency flag
does not come into play because flush_to_ldisc()
is called directly instead of
through tty_flip_buffer_push().
TTY_DONT_FLIP is only set in read_chan().
If read_chan() is not running, TTY_DONT_FLIP is not
set and does not prevent buffers from flipping
if the ISR calls flush_to_ldisc() directly
while ldisc->receive_buf() is running.
The answer seems to be: don't call
flush_to_ldisc directly like the current
serial driver does.
-- Paul Fulghum paulkf@microgate.com - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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