Bug 13078

Summary: Xephyr 1.4 crash in find_mesa_visual when running KDE4
Product: xorg Reporter: Brice Goglin <brice.goglin>
Component: Server/DDX/XephyrAssignee: Dodji Seketeli <dodji>
Status: RESOLVED FIXED QA Contact: Xorg Project Team <xorg-team>
Severity: normal    
Priority: medium    
Version: 7.3 (2007.09)   
Hardware: Other   
OS: All   
URL: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=449238
Whiteboard:
i915 platform: i915 features:
Bug Depends on:    
Bug Blocks: 12560    

Description Brice Goglin 2007-11-04 06:08:28 UTC 
Bug reported by Harri Pitkänen in the Debian BTS today.

He's trying to run a KDE4 development snapshot *within* Xephyr 1.4. It causes a crash with the following backtrace. The bug couldn't be reproduced with a stable KDE or Gnome. It's probably related to some Compositing stuff that KDE4 enables and I guess Xephyr does not support all of them yet...

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x2ba8310e7d30 (LWP 2510)]
0x000000000053080d in find_mesa_visual (screen=0xbf2350, vid=58) at ../../../GL/glx/glxglcore.c:290
290         return (modes != NULL) ? mesaScreen->xm_vis[i] : NULL;
(gdb) bt full
#0  0x000000000053080d in find_mesa_visual (screen=0xbd82e0, vid=58) at ../../../GL/glx/glxglcore.c:290
        mesaScreen = (__GLXMESAscreen *) 0xbd82e0
        modes = (const __GLcontextModes *) 0xd907f0
        i = 0
#1  0x000000000053066a in __glXMesaScreenCreateContext (screen=0xbd82e0, modes=0xd907f0, baseShareContext=0x0) at ../../../GL/glx/glxglcore.c:237
        context = (__GLXMESAcontext *) 0xda0350
        shareContext = (__GLXMESAcontext *) 0x0
        xm_vis = (XMesaVisual) 0x3a00000000
        xm_share = (XMesaContext) 0xd907f0
#2  0x000000000054f883 in DoCreateContext (cl=0xd90730, gcId=12582918, shareList=0, visual=58, screen=0, isDirect=0 '\0') at ../../../GL/glx/glxcmds.c:206
        client = (ClientPtr) 0xd92870
        pVisual = (VisualPtr) 0xbed018
        pScreen = (ScreenPtr) 0xd59f90
        glxc = (__GLXcontext *) 0x8a4f60
        shareglxc = (__GLXcontext *) 0x0
        modes = (__GLcontextModes *) 0xd907f0
        pGlxScreen = (__GLXscreen *) 0xbd82e0
        i = 1
#3  0x000000000054f9c4 in __glXDisp_CreateContext (cl=0xd90730, pc=0xd9ff70 "\225\003\006") at ../../../GL/glx/glxcmds.c:249
        req = (xGLXCreateContextReq *) 0xd9ff70
#4  0x0000000000530276 in __glXDispatch (client=0xd92870) at ../../../GL/glx/glxext.c:561
        rendering = 0 '\0'
        stuff = (xGLXSingleReq *) 0xd9ff70
        opcode = 3 '\003'
        proc = (__GLXdispatchSingleProcPtr) 0x54f96d <__glXDisp_CreateContext>
        cl = (__GLXclientState *) 0xd90730
        retval = 0
#5  0x00000000004fabf5 in XaceCatchExtProc (client=0xd92870) at ../../Xext/xace.c:299
        stuff = (xReq *) 0x0
        major = 149
        ext = (ExtensionEntry *) 0xbf21c0
#6  0x000000000046600f in Dispatch () at ../../dix/dispatch.c:502
        clientReady = (int *) 0x7fff4168a710
        result = 24
        client = (ClientPtr) 0xd92870
        nready = 0
        icheck = (HWEventQueuePtr *) 0xbc1df0
        start_tick = 2140
#7  0x000000000044a09f in main (argc=2, argv=0x7fff4168aca8, envp=0x7fff4168acc0) at ../../dix/main.c:452
        i = 1
        j = 2
        k = 2
        error = 1768139776
        xauthfile = 0x0
        alwaysCheckForInput = {0, 1}


In case it matters, here are the latest KDE messages before the crash:
  kdeinit4: Got EXEC_NEW 'kwin' from launcher.
  kdeinit4: preparing to launch /home/kde/kde/bin/kwin
  klauncher(3750)/kio (KLauncher) KLauncher::processRequestReturn: "kwin" (pid 3764) up and running.
  kwin(3764) KWin::Extensions::init: Extensions: shape: 0x "11"  composite: 0x "4"  render: 0x "a"  fixes: 0x "40"
  kwin(3764) KWin::CompositingPrefs::detect: glx version is  1 . 2
Comment 1 Dodji Seketeli 2007-11-12 12:28:17 UTC 
Okay, this is due to the fact that Xephyr actually does not provide any OpenGL renderer in 1.4.x.
But as it was compiled with --enable-glx, the GLX extension was enabled, accepting GL requests. Those request could not be handled properly by the software GL renderer (mesa) because it was not initiliased. So Xephyr crashes.

A proper possible solution is to disable the GLX extension for now. Xephyr in master will provide an accelerated GL renderer.

So a I have pushed the fix 007e2239cf65535c4df3486e7b2cc42a4e86eb56 to fix the crach.

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