Messages in this thread | | | Date | Wed, 24 Aug 2011 13:47:37 +0200 | From | Jiri Slaby <> | Subject | Re: patch "TTY: remove tty_locked" added to tty tree |
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On 08/24/2011 01:20 PM, Arnd Bergmann wrote: > It's not clear to me what state->mutex protects in the serial_core, but > it has been around forever (used to be called state->sem)
It was actually moved in uart_close back in 2003. Formerly (when there was only a coarse grained port_sem) it was right before uart_shutdown. But there were some flags to handle some races. I'm not sure whether the flags protected any race here though.
> and is held in > all uart functions, which is at least consistent. IIRC what Alan's plan > for this was, uart_close should eventually get changed to use > tty_port_close_start or even tty_port_close. Maybe the time for that has > come now, lacking better alternatives?
Yes, I have such a patch in my queue. But it's not easy to get there. You may take a look at: http://decibel.fi.muni.cz/gitweb/?p=linux.git;a=shortlog;h=refs/heads/devel
But it's still far from ready. And yet, in the queue, I still have port->mutex locked before tty_port_close_start like it is now.
> A lot of other drivers call tty_port_close_start() before taking port->mutex.
Yes, that's true. That's why I wrote that before. But most of the drivers doesn't have so complex locking dependencies like uart.
thanks, -- js suse labs
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