> -----Original Message-----
> From: Chris Wilson <ch...@chris-wilson.co.uk>
> Sent: Thursday, July 23, 2020 10:21 AM
> To: intel-gfx@lists.freedesktop.org
> Cc: dri-de...@lists.freedesktop.org; Chris Wilson <ch...@chris-wilson.co.uk>;
> Tang, CQ <cq.t...@intel.com>; Vetter, Daniel <daniel.vet...@intel.com>;
> sta...@vger.kernel.org
> Subject: [PATCH 2/3] drm/i915/gem: Move context decoupling from
> postclose to preclose
>
> Since the GEM contexts refer to other GEM state, we need to nerf those
> pointers before that state is freed during drm_gem_release(). We need to
> move i915_gem_context_close() from the postclose callback to the preclose.
>
> In particular, debugfs likes to peek into the GEM contexts, and from there
> peek at the drm core objects. If the context is closed during the peeking, we
> may attempt to dereference a stale core object.
>
> Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> Cc: CQ Tang <cq.t...@intel.com>
> Cc: Daniel Vetter <daniel.vet...@intel.com>
> Cc: sta...@vger.kernel.org
> ---
> drivers/gpu/drm/i915/i915_drv.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.c
> b/drivers/gpu/drm/i915/i915_drv.c index 5fd5af4bc855..15242a8c70f7 100644
> --- a/drivers/gpu/drm/i915/i915_drv.c
> +++ b/drivers/gpu/drm/i915/i915_drv.c
> @@ -1114,11 +1114,15 @@ static void i915_driver_lastclose(struct
> drm_device *dev)
> vga_switcheroo_process_delayed_switch();
> }
>
> +static void i915_driver_preclose(struct drm_device *dev, struct
> +drm_file *file) {
> + i915_gem_context_close(file);
> +}
> +
> static void i915_driver_postclose(struct drm_device *dev, struct drm_file
> *file) {
> struct drm_i915_file_private *file_priv = file->driver_priv;
>
> - i915_gem_context_close(file);
> i915_gem_release(dev, file);
Now we separate i915_gem_context_close() from i915_gem_release() and other
freeing code in postclose(), is there any side effect to allow code to run in
between?
Can we move all postclose() code into preclose()?
--CQ
>
> kfree_rcu(file_priv, rcu);
> @@ -1850,6 +1854,7 @@ static struct drm_driver driver = {
> .release = i915_driver_release,
> .open = i915_driver_open,
> .lastclose = i915_driver_lastclose,
> + .preclose = i915_driver_preclose,
> .postclose = i915_driver_postclose,
>
> .gem_close_object = i915_gem_close_object,
> --
> 2.20.1
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