Re: [Intel-gfx] [PATCH] drm/i915: Perform execbuffer object locking as a separate step

["Tang, CQ" <cq.tang@intel.com>]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@lists.freedesktop.org> On Behalf Of
> Thomas Hellström
> Sent: Tuesday, June 15, 2021 4:36 AM
> To: intel-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>; Auld, Matthew
> <matthew.auld@intel.com>
> Subject: [Intel-gfx] [PATCH] drm/i915: Perform execbuffer object locking as a
> separate step
> 
> To help avoid evicting already resident buffers from the batch we're
> processing, perform locking as a separate step.
> 
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 25 ++++++++++++++++--
> -
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index 201fed19d120..394eb40c95b5 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -922,21 +922,38 @@ static int eb_lookup_vmas(struct i915_execbuffer
> *eb)
>  	return err;
>  }
> 
> -static int eb_validate_vmas(struct i915_execbuffer *eb)
> +static int eb_lock_vmas(struct i915_execbuffer *eb)
>  {
>  	unsigned int i;
>  	int err;
> 
> -	INIT_LIST_HEAD(&eb->unbound);
> -
>  	for (i = 0; i < eb->buffer_count; i++) {
> -		struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
>  		struct eb_vma *ev = &eb->vma[i];
>  		struct i915_vma *vma = ev->vma;
> 
>  		err = i915_gem_object_lock(vma->obj, &eb->ww);
>  		if (err)
>  			return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int eb_validate_vmas(struct i915_execbuffer *eb) {
> +	unsigned int i;
> +	int err;
> +
> +	INIT_LIST_HEAD(&eb->unbound);
> +
> +	err = eb_lock_vmas(eb);
> +	if (err)
> +		return err;
> +
> +	for (i = 0; i < eb->buffer_count; i++) {
> +		struct drm_i915_gem_exec_object2 *entry = &eb->exec[i];
> +		struct eb_vma *ev = &eb->vma[i];
> +		struct i915_vma *vma = ev->vma;
> 
>  		err = eb_pin_vma(eb, entry, ev);
>  		if (err == -EDEADLK)

Thomas, just checked eb_pin_vma(), it calls i915_vma_pin_ww(), if the object is already locked, under what condition these calls still return -EDEADLK?

--CQ

> --
> 2.31.1
> 
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