Xorg-1.20.1 crashes when using glamor on top of llvmpipe

[Ray Strode]

hi,

what version of mesa?

might be


https://cgit.freedesktop.org/mesa/mesa/commit/?id=9baff597ce021f7691187b0d1d1bbc16d07b13e1

Ray

On Thu, Aug 30, 2018, 5:00 PM Hans de Goede <hdegoede at redhat.com> wrote:

> Hi,
>
> On 30-08-18 22:48, Hans de Goede wrote:
> > HI all,
> >
> > I've been debugging some strange crashes with Xorg-1.20.1 inside
> > a virtualbox guest and I can use some help with this.
> >
> > At first Xorg completely failed to start, running it under
> > gdbserver showed a backtrace pointing to a lazy symbol lookup
> > failure triggered by:
> >
> > drmmode_display.c:905:
> >          return gbm_bo_get_stride(bo->gbm);
> >
> > Which is part of:
> >
> >
> > uint32_t
> > drmmode_bo_get_pitch(drmmode_bo *bo)
> > {
> > #ifdef GLAMOR_HAS_GBM
> >      if (bo->gbm)
> >          return gbm_bo_get_stride(bo->gbm);
> > #endif
> >
> >      return bo->dumb->pitch;
> > }
> >
> > Strange enough a LD_PRELOAD of libgbm does not
> > fix this and libgbm already gets dragged in by
> > libglamor_egl.so so this should not be a problem.
> >
> > Still I tried this change:
> >
> > --- a/hw/xfree86/drivers/modesetting/Makefile.am
> > +++ b/hw/xfree86/drivers/modesetting/Makefile.am
> > @@ -39,7 +39,7 @@ AM_CPPFLAGS = \
> >
> >   modesetting_drv_la_LTLIBRARIES = modesetting_drv.la
> >   modesetting_drv_la_LDFLAGS = -module -avoid-version
> > -modesetting_drv_la_LIBADD = $(UDEV_LIBS) $(DRM_LIBS)
> > +modesetting_drv_la_LIBADD = $(UDEV_LIBS) $(DRM_LIBS) $(GBM_LIBS)
> >   modesetting_drv_ladir = @moduledir@/drivers
> >
> >   modesetting_drv_la_SOURCES = \
> >
> > And now Xorg will start, still very weird since the
> > exact same Xorg binaries work fine on Intel integrated
> > gfx where the gbm_bo_get_stride() call also happens ...
> >
> >
> > So with this "fix" it starts, but it crashes as soon as I resize the
> > vm-window and thus the screen gets resized:
> >
> > bt
> > #0  OsSigHandler (signo=11, sip=0x7ffc160ad2f0, unused=0x7ffc160ad1c0)
> >      at osinit.c:114
> > #1  <signal handler called>
> > #2  miModifyPixmapHeader (pPixmap=0x28c4460, width=1920, height=992,
> depth=-1,
> >      bitsPerPixel=-1, devKind=7680, pPixData=0x0) at miscrinit.c:64
> > #3  0x00007fdc13d64471 in drmmode_xf86crtc_resize (scrn=0x21751f0,
> width=1920,
> >      height=992) at drmmode_display.c:3166
> > #4  0x00000000004bb9d8 in xf86RandR12ScreenSetSize (pScreen=0x23dc9b0,
> >      width=1920, height=992, mmWidth=508, mmHeight=262) at
> xf86RandR12.c:698
> > #5  0x00000000005092f0 in ProcRRSetScreenSize (client=0x29c6af0)
> >      at rrscreen.c:289
> > #6  0x000000000043fcee in Dispatch () at dispatch.c:478
> >
> > And miscrinit.c:64 is hte "{" of:
> >
> > Bool
> > miModifyPixmapHeader(PixmapPtr pPixmap, int width, int height, int depth,
> >                       int bitsPerPixel, int devKind, void *pPixData)
> > {
> >      if (!pPixmap)
> >          return FALSE;
> >
> > Which is a strange place to crash. Even more weird after adding a
> > breakpoint a bit before drmmode_display.c:3166, I get a segfault
> > while stepping through earlier lines, pointing at SmartScheduleTimer()
> > and specifically again at the opening "{" as if something is wrong with
> > the stack and the stack cannot handle function calls being stacked one
> > level deeper.
> >
> > This makes me wonder if this is a stack depth/overflow issue, does the
> > xserver have code somewhere to limit its stacksize and could we be
> > hitting that ?
> >
> > Or maybe a bad interaction with gcc-s stack protection?
> >
> > This feels as if we are hitting a guard page at the end of the stack
> > here?
>
> One important thing which I only put in the subject, this happens
> when using glmamor with llvmpipe, something which is new in 1.20,
> older xservers never used glamor on llvmpipe. Things work fine
> if I disable glamor in a xorg.conf snippet.
>
> Arguably we should disable glamor when running on llvmpipe because
> of performance reasons, still these crashes should not happen.
>
> Regards,
>
> Hans
>
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