[PATCH v2] drm/i915: Flush buffer pools on driver remove

[Matt Roper]

On Fri, Sep 24, 2021 at 06:38:25PM +0200, Janusz Krzysztofik wrote:
> We currently do an explicit flush of the buffer pools within the call path
> of drm_driver.release(); this removes all buffers, regardless of their age,
> freeing the buffers' associated resources (objects, adress space areas).
> However there is other code that runs within the drm_driver.release() call
> chain that expects objects and their associated address space areas have
> already been flushed.
> 
> Since buffer pools auto-flush old buffers once per second in a worker
> thread, there's a small window where if we remove the driver while there
> are still objects in buffers with an age of less than one second, the
> assumptions of the other release code may be violated.
> 
> By moving the flush to driver remove (which executes earlier via the
> pci_driver.remove() flow) we're ensuring that all buffers are flushed and
> their associated objects freed before some other code in
> pci_driver.remove() flushes those objects so they are released before
> _any_ code in drm_driver.release() that check completness of those
> flushes executes.
> 
> v2: Reword commit descriptiom as suggested by Matt.
> 
> Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Matt Roper <matthew.d.roper at intel.com>

Reviewed-by: Matt Roper <matthew.d.roper at intel.com>

and applied to drm-intel-gt-next (with a couple minor spelling fixes in
the commit message).  Thanks for the patch.


Matt

> ---
>  drivers/gpu/drm/i915/gt/intel_gt.c             | 2 ++
>  drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c | 2 --
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt.c b/drivers/gpu/drm/i915/gt/intel_gt.c
> index 4037c3778225..5b3acf2b064e 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt.c
> @@ -741,6 +741,8 @@ void intel_gt_driver_remove(struct intel_gt *gt)
>  	intel_uc_driver_remove(&gt->uc);
>  
>  	intel_engines_release(gt);
> +
> +	intel_gt_flush_buffer_pool(gt);
>  }
>  
>  void intel_gt_driver_unregister(struct intel_gt *gt)
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
> index aa0a59c5b614..acc49c56a9f3 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_buffer_pool.c
> @@ -245,8 +245,6 @@ void intel_gt_fini_buffer_pool(struct intel_gt *gt)
>  	struct intel_gt_buffer_pool *pool = &gt->buffer_pool;
>  	int n;
>  
> -	intel_gt_flush_buffer_pool(gt);
> -
>  	for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
>  		GEM_BUG_ON(!list_empty(&pool->cache_list[n]));
>  }
> -- 
> 2.25.1
> 

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795