[Dri-devel] mga lockup because of drmGetLock with flag=0

[FT R. <ma...@mu...>]

Hi
Thanks to all who provided debug info and the XF86 team for the module
debugger. I have looked more into the X lockups on mga DRI (both from
xf86 cvs ond DRI cvs). The lockup can be replicated by repeatedly (not
concurrently) executing very simple code, I have put the code at:
ftp://news.icns.com/pub/lesson2.c
(detailed stack trace for X is at the end of the message, trace for the
application at lockup is at ftp://news.icns.com/pub/lesson2.app.out )


After the lockup I can see that last recognizable thing X
did was:

#0  0x400e5f24 in __ioctl ()
#1  0xbffff5cc in ?? ()
#2  0x864758c in drmGetLock (fd=6, context=1, flags=0) at xf86drm.c:714


I dont see the value of drmLockFlags as 0 defined in xf86drm.h. Plus
shouldnt the next thing in the stack be something like:? 

#1  xf86ioctl (fd=6, request=??, argp=??) at 
libc_wrapper.c:43  

which it sure isnt. I dont know why it ends up at:

#1  0xbffff5cc in ?? ()

Does that qualify for a bug, if it is is it known?,
should I debug more, what should I do?. I will try looking more into it
though. 

Another thing I noticed that drmGetLock(??,??, flags=10) is being called
everytime on mouse clicks. Is it necessary to get DRM_HALT_ALL_QUEUES.

Thanks
FT

The stack trace of the Xserver


#0  0x400e5f24 in __ioctl ()
#1  0xbffff5cc in ?? ()
#2  0x864758c in drmGetLock (fd=6, context=1, flags=0) at xf86drm.c:714
#3  0x85e155e in DRILock (pScreen=0x8709db0, flags=0) at dri.c:1589
#4  0x854b4ec in MGAWakeupHandler (screenNum=0, wakeupData=0x0, 
    result=4294967295, pReadmask=0x81b94c0) at mga_wrap.c:75
#5  0x85e0c5d in DRIWakeupHandler (wakeupData=0x0, result=-1, 
    pReadmask=0x81b94c0) at dri.c:1081
#6  0x80ab17c in WakeupHandler (result=-1, pReadmask=0x81b94c0)
    at dixutils.c:459
#7  0x80c380f in WaitForSomething (pClientsReady=0xbffff8e0) at WaitFor.c:354
#8  0x80a51c4 in Dispatch () at dispatch.c:382
#9  0x80b49e8 in main (argc=4, argv=0xbffffd64) at main.c:429
#10 0x400531eb in __libc_start_main (main=0x80b4530 <main>, argc=4, 
    argv=0xbffffd64, init=0x806a99c <_init>, fini=0x815ff6c <_fini>, 
    rtld_fini=0x4000a610 <_dl_fini>, stack_end=0xbffffd5c)
    at ../sysdeps/generic/libc-start.c:90