On Mon, Jun 20, 2011 at 4:03 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Mon, 20 Jun 2011, Mandeep Singh Baines wrote: > >> Hi Dave, >> >> I think this change is causing a regression I'm seeing in panic. >> Before this change, I'd get a >> reboot on panic (we've configured as such). >> >> With this change, my machine gets wedged if the machine is running in >> X when the panic occurs. >> >> I traced the code flow to this: >> >> bust_spinlocks(0); >> ->unblank_screen(); >> ->do_unblank_screen(0); >> ->vc->vc_sw->con_blank(vc, 0, 0); >> ->fbcon_blank(vc, 0, 0); >> ->update_screen(vc); >> ->redraw_screen(vc, 0); >> ->vc->vc_sw->con_switch(vc); >> ->fbcon_switch(vc); >> ->ops->update_start(info); >> ->bit_update_start(info); >> ->fb_pan_display(info, &ops->var); >> ->info->fbops->fb_pan_display(var, info); >> ->drm_fb_helper_pan_display(var, info); >> ->mutex_lock(&dev->mode_config.mutex); *this blocks* >> >> With this change, there is now a lot going on in the panic path. Stuff >> that I'm not sure is safe when panicking. In addition to the >> mutex_lock, there is also a del_timer_sync() >> now happening in the context of panic(). >> >> I see this bug with a 2.6.38 kernel but did a quick scan of a newer >> kernels and did not see anything that changed in this path so I >> suspect its still there. >> >> Reverting this change fixes the regression. >> > > Chris Fowler reports something similar when running 2.6.38 by inducing a > kernel panic via the oom killer -- see > http://marc.info/?l=linux-kernel&m=130805985022791. I've added him to the > cc so he can participate in the thread and cherry-pick any fixes (last > status update was that he was going to be trying 2.6.38.8). > One potential fix might be to convert the mutex_lock to a try if oops_in_progress but I suspect oops_in_progress checks may be needed in a bunch of other places in the screen_unblank code path. ------------------------------------------------------------------------------ EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev -- _______________________________________________ Dri-devel mailing list Dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/dri-devel _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
