On Tue, 17 May 2005, Lorenzo Colitti wrote:
Dave Airlie wrote:I reapplied Vladimir's fix and the machine doesn't lock up any more. Maybe the
fix should be checked in to CVS again?
http://cvs.freedesktop.org/xorg/xc/programs/Xserver/hw/xfree86/drivers/ati/radeon_mergedfb.c?rev=1.9&view=log
v 1.7 backs it out because it is buggy...
I know, I read the checkin comment.
However, is "buggy" better than "locked up hard"?
This "buggy" part was due to the fix breaking down completely when used on SMP machines.
The "correct" fix is to turn off "SilkenMouse".
What happens is that by default the Xserver is two-threaded - there is a main thread that processes graphics requests via X11 connection and a second thread that responds to mouse movements.
Now, this is not not quite right either, as (AFAIK) there are no actual threads used - rather the mouse movement is triggerred by a signal generated when more data becomes available.
Regardless, it is possible for mouse code to execute bypassing the usual Xserver entry functions. This makes for smoother mouse movement and lets you observe "windows are frozen but mouse moves" lockups.
Of course, in your case it is necessary to synchronize mouse update with Mesa driver and bypassing those is bad.
Again, a correction: "necessary" is not due to requirement of the software
(mouse does not care what 3d windows are drawing) nor any known features of the hardware, except that it looks like reading registers while some 3d
operations are in progress causes a lockup.
We do not have good evidence that this is what happens, and whatever documentation we have (and valuable input from Michael Danzer) point out that something else is wrong as hardware should allow reading cursor registers at arbitrary times.
So, if you do not have SMP machine, put the "fix" back, or just disable SilkenMouse.
best
Vladimir Dergachev
PS If anyone has more current knowledge on this issue - please correct me !
Cheers, Lorenzo
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