linux-kernel - Re: [PATCH v2] drm/i915: Fix BUG in i915

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Date:	Thu, 12 Mar 2015 10:28:56 +0200
From:	Jani Nikula <jani.nikula@...ux.intel.com>
To:	Xi Ruoyao <xry111@...look.com>, daniel.vetter@...el.com,
	airlied@...ux.ie
Cc:	intel-gfx@...ts.freedesktop.org, dri-level@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org, Xi Ruoyao <xry111@...look.com>,
	"Roper\, Matthew D" <matthew.d.roper@...el.com>
Subject: Re: [PATCH v2] drm/i915: Fix BUG in i915_gem.c when switch to console

On Thu, 12 Mar 2015, Xi Ruoyao <xry111@...look.com> wrote:
> In intel_crtc_page_flip, intel_display.c, the code changed the framebuffer
> assigned to plane crtc->primary by
>
> crtc->primary->fb = fb;
>
> However, it forgot to change crtc->primary->state->fb. However, when we
> switch to console, some kernel code will read crtc->primary->state->fb
> to get the framebuffer assigned to crtc->primaty. Then a framebuffer
> object can be unpinned twice and a kernel BUG will be produced in i915_gem.c.
>
> So, update crtc->primary->state->fb in intel_display.c using
> drm_atomic_set_fb_for_plane to fix the BUG.
>
> Signed-off-by: Xi Ruoyao <xry111@...look.com>
> Fixed: Bug 93711 <https://bugzilla.kernel.org/show_bug.cgi?id=93711>

Is this a problem with drm-intel-nightly? In particular see

commit afd65eb4cc0578a9c07d621acdb8a570e2782bf7
Author: Matt Roper <matthew.d.roper@...el.com>
Date:   Tue Feb 3 13:10:04 2015 -0800

    drm/i915: Ensure plane->state->fb stays in sync with plane->fb

Matt, do you think this fixes the described issue? Can we backport to
drm-intel-fixes (and v4.0)?

BR,
Jani.



> ---
>  Sorry, the previous patch is mangled by email client, so I am re-sending it.
>
>  drivers/gpu/drm/i915/intel_display.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index e730789..97083fd 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -37,6 +37,7 @@
>  #include <drm/i915_drm.h>
>  #include "i915_drv.h"
>  #include "i915_trace.h"
> +#include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_dp_helper.h>
>  #include <drm/drm_crtc_helper.h>
> @@ -9816,6 +9817,7 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
>  	drm_gem_object_reference(&obj->base);
>  
>  	crtc->primary->fb = fb;
> +	drm_atomic_set_fb_for_plane(crtc->primary->state, fb);
>  
>  	work->pending_flip_obj = obj;
>  
> -- 
> 1.9.1
>

-- 
Jani Nikula, Intel Open Source Technology Center
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