Re: Hang in uart_block_til_ready()

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Sun, Apr 02, 2006 at 05:17:39PM +0200, Michael Hanselmann wrote:
> Hello Russell
> 
> On Sun, Apr 02, 2006 at 03:38:27PM +0100, Russell King wrote:
> > On Sun, Apr 02, 2006 at 03:51:38PM +0200, Michael Hanselmann wrote:
> > > I've discovered a problem where I'm not sure wether it's an error in the
> > > kernel or in the hardware.
> 
> > It's neither - it's a bug in your test program.  If you want "callout"
> > semantics, open the port using O_NONBLOCK mode.
> 
> I've now patched screen(1) and it works, but one thing is amazing me.
> The other computer I wrote about has the serial console on ttyS0 and
> starting screen(1) on the serial console works. Here's the relevant
> strace part:

Have you checked the state of the DCD line in both cases?  Look in
/proc/tty/driver/serial.

> Am I going correct that this is a bug in screen(1) and it only works on
> the first box by some mysterious reason? Mabye some timing issue?

Probably "works" on the first box because it happens to have DCD asserted
on the real serial port.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core