mouse interactivity (Re: svn commit: r182109 - head/sys/dev/syscons)

Kris Kennaway kris at
Tue Aug 26 13:20:39 UTC 2008

Marius Nünnerich wrote:
> On Mon, Aug 25, 2008 at 4:19 PM, Ed Schouten <ed at> wrote:
>> * Kris Kennaway <kris at> wrote:
>>> Ed Schouten wrote:
>>>> Author: ed
>>>> Date: Sun Aug 24 15:20:44 2008
>>>> New Revision: 182109
>>>> URL:
>>>> Log:
>>>>   Make sysmouse(4) use its own locks, instead of using Giant.
>>>>     When I changed syscons(4) to work with the MPSAFE TTY code, I just
>>>>   locked all device nodes down using the compatibility feature that allows
>>>>   you to override the TTY's lock (Giant in this case). Upon closer
>>>>   inspection, it seems sysmouse(4) only has two internal variables that
>>>>   need locking: mouse_level and mouse_status.
>>>>     I haven't done any performance benchmarks on this, though I think
>>>> it
>>>>   won't have any dramatic improvements on the system. It is good to get
>>>>   rid of Giant here, because the third argument of tty_alloc() has only
>>>>   been added to ease migration to MPSAFE TTY. It should not be used when
>>>>   not needed.
>>>>     While there, remove SC_MOUSE, which is a leftover from the MPSAFE
>>>> TTY
>>>>   import.
>>> This might help mouse interactivity for desktop users that have legacy
>>> Giant-locked systems in use (e.g. busy MSDOS filesystems, giant-locked
>>> disk drivers), etc.
>> Yes, but only a very very little bit. moused still delivers the input to
>> /dev/consolectl, which is still Giant locked. The part where the Xorg
>> server reads from /dev/sysmouse is now Giant-free.
> Are you going to lock that one too? I have some problems with a sluggish PS/2
> mouse when Firefox runs a heavily javascripted site (though it is way better
> now that I can use nvidia(4) again without crashing).

Unless you fit into a situation like the one I described, it doesn't 
sound like the giant locking is the problem for you.  You can check by 
enabling lock profiling.


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