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

Ed Schouten ed at
Mon Aug 25 14:19:52 UTC 2008

* 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.

 Ed Schouten <ed at>
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