[Mesa-dev] [PATCH mesa] wayland: Disable prime support on buggy kernels

[Ander Conselvan de Oliveira]

On 05/08/2013 11:50 PM, Jonas Ådahl wrote:
> On Tue, Apr 23, 2013 at 3:54 PM, Ander Conselvan de Oliveira
> <ander.conselvan.de.oliveira at intel.com> wrote:
>> Linux kernel 3.8 shipped with a bug in the prime fd passing code that
>> makes it unreliable. As of this writing, it seems unlikely that 3.9
>> will contain the fix for the issue.
>>
>> This patch disable prime support when running on top of those kernels,
>> in order to prevent unexpected behavior when running a Wayland
>> compositor.
>>
>> Commit be8a42ae60addd8b6092535c11b42d099d6470ec in Linus tree introduces
>> the problem, which can be fixed by the patch below (not upstream yet):
>> http://lists.freedesktop.org/archives/dri-devel/2013-April/037716.html
>> ---
>>   src/egl/drivers/dri2/egl_dri2.c |   36 +++++++++++++++++++++++++++++++++++-
>>   1 file changed, 35 insertions(+), 1 deletion(-)
>>
>> diff --git a/src/egl/drivers/dri2/egl_dri2.c b/src/egl/drivers/dri2/egl_dri2.c
>> index 06a21d7..13b9107 100644
>> --- a/src/egl/drivers/dri2/egl_dri2.c
>> +++ b/src/egl/drivers/dri2/egl_dri2.c
>> @@ -38,6 +38,7 @@
>>   #include <GL/internal/dri_interface.h>
>>   #include <sys/types.h>
>>   #include <sys/stat.h>
>> +#include <sys/utsname.h>
>>
>>   #include "egl_dri2.h"
>>
>> @@ -1557,6 +1558,38 @@ static struct wayland_drm_callbacks wl_drm_callbacks = {
>>   };
>>
>>   static EGLBoolean
>> +kernel_prime_support_not_buggy()
>> +{
>> +   struct utsname un;
>> +
>> +   /* Linux kernel 3.8 shipped with a bug in the prime fd passing code that
>> +    * makes it unreliable. As of this writing, it seems unlikely that 3.9
>> +    * will contain the fix for the issue. Disable prime support when running
>> +    * on top of those kernels, in order to prevent unexpected behavior when
>> +    * running a Wayland compositor.
>> +    *
>> +    * Commit be8a42ae60addd8b6092535c11b42d099d6470ec in Linus tree introduces
>> +    * the problem, which can be fixed by the patch below (not upstream yet):
>> +    * http://lists.freedesktop.org/archives/dri-devel/2013-April/037716.html
>> +    */
>> +   if (uname(&un) == -1) {
>> +      _eglLog(_EGL_INFO,
>> +              "DRI2: wayland prime support disabled: unknown kernel version");
>> +      return EGL_FALSE;
>> +   }
>> +
>> +   if (strncmp(un.sysname, "Linux", strlen("Linux")) == 0 &&
>> +       (strncmp(un.release, "3.8.", strlen("3.8.")) == 0 ||
>> +        strncmp(un.release, "3.9.", strlen("3.9.")) == 0)) {
>
> I think if we should test against kernel releases we can disable for
> anything older than the first release that has the fix as it doesn't
> seem to work on older versions either. At least in my case I get what
> looks like the same issue when prime support enabled when running
> kernel version 3.5.

Your distro probably picked up the patch that introduces the bug. But 
anyway, I think this patch should just be dropped. It doesn't really 
solve the issue.

There's no Mesa release with prime support yet, so I guess we should 
just disable it for now, until things are solved on the kernel side.

Cheers,
Ander

>
> Jonas
>
>> +         _eglLog(_EGL_INFO,
>> +                 "DRI2: wayland prime support disabled: buggy kernel");
>> +         return EGL_FALSE;
>> +   }
>> +
>> +   return EGL_TRUE;
>> +}
>> +
>> +static EGLBoolean
>>   dri2_bind_wayland_display_wl(_EGLDriver *drv, _EGLDisplay *disp,
>>                               struct wl_display *wl_dpy)
>>   {
>> @@ -1575,7 +1608,8 @@ dri2_bind_wayland_display_wl(_EGLDriver *drv, _EGLDisplay *disp,
>>      ret = drmGetCap(dri2_dpy->fd, DRM_CAP_PRIME, &cap);
>>      if (ret == 0 && cap == (DRM_PRIME_CAP_IMPORT | DRM_PRIME_CAP_EXPORT) &&
>>          dri2_dpy->image->base.version >= 7 &&
>> -       dri2_dpy->image->createImageFromFds != NULL)
>> +       dri2_dpy->image->createImageFromFds != NULL &&
>> +       kernel_prime_support_not_buggy())
>>         flags |= WAYLAND_DRM_PRIME;
>>
>>      dri2_dpy->wl_server_drm =
>> --
>> 1.7.10.4
>>
>> _______________________________________________
>> mesa-dev mailing list
>> mesa-dev at lists.freedesktop.org
>> http://lists.freedesktop.org/mailman/listinfo/mesa-dev

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