lkml.org 
[lkml]   [2011]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: patch "TTY: remove tty_locked" added to tty tree
    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


    \
     
     \ /
      Last update: 2011-08-24 13:49    [W:2.760 / U:0.176 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site