Re: kern/49838: radeon drm2 kernel panic

[David Holland <dholland-bugs%netbsd.org@localhost>]

The following reply was made to PR kern/49838; it has been noted by GNATS.

From: David Holland <dholland-bugs%netbsd.org@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: kern/49838: radeon drm2 kernel panic
Date: Sat, 26 Nov 2016 10:04:48 +0000

 On Mon, Apr 13, 2015 at 04:30:00PM +0000, Tobias Nygren wrote:
  >  Found a workaround for the teapot segfault. the r600 driver in MesaLib
  >  10.x runs a separate worker thread for DRM_IOCTL_RADEON_CS if it
  >  detects multiprocessor hardware. It gets a segfault when the worker
  >  thread runs it's ioctl while the other thread loads things into the
  >  graphics pipeline. Note sure if this is a Mesa or kernel bug.
  >  
  >  Removing this code from Mesa's
  >  radeon_drm_winsys.c:radeon_drm_winsys_create() makes it not crash any
  >  more.
  >  
  >  -   if (ws->num_cpus > 1 && debug_get_option_thread())
  >  -       ws->thread = pipe_thread_create(radeon_drm_cs_emit_ioctl, ws);
 
 Also it turns out that one can test this hack a lot more easily than
 by removing/commenting out these lines and recompiling:
 
    % setenv RADEON_THREAD FALSE
    % ./teapot
 
 This is not making it run for me but at the moment it does make the
 difference between glxgears running or not.
 
 (...this after patching gallium to use pthreads, without which it
 doesn't even load. go figure.)
 
 -- 
 David A. Holland
 dholland%netbsd.org@localhost