Re: [Intel-gfx] [PATCH 3/4] drm/ttm: Don't leak a resource on eviction error

[Thomas Hellström]

On 6/22/23 15:55, Andi Shyti wrote:
> Hi Thomas,
>
> On Thu, Jun 22, 2023 at 12:14:11PM +0200, Thomas Hellström wrote:
> > On eviction errors other than -EMULTIHOP we were leaking a resource.
> > Fix.
> >
> > Fixes: 403797925768 ("drm/ttm: Fix multihop assert on eviction.")
> > Cc: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
> > Cc: Christian König <christian.koenig@xxxxxxx>
> > Cc: Christian Koenig <christian.koenig@xxxxxxx>
> > Cc: Huang Rui <ray.huang@xxxxxxx>
> > Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> > Cc: <stable@xxxxxxxxxxxxxxx> # v5.15+
> > Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/ttm/ttm_bo.c | 16 ++++++++--------
> >   1 file changed, 8 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> > index 615d30c4262d..89530f2a027f 100644
> > --- a/drivers/gpu/drm/ttm/ttm_bo.c
> > +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> > @@ -462,14 +462,14 @@ static int ttm_bo_evict(struct ttm_buffer_object *bo,
> >   	ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
> >   	if (ret == -EMULTIHOP) {
> >   		ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem, ctx, &hop);
> > -		if (ret) {
> > -			if (ret != -ERESTARTSYS && ret != -EINTR)
> > -				pr_err("Buffer eviction failed\n");
> > -			ttm_resource_free(bo, &evict_mem);
> > -			goto out;
> > -		}
> > -		/* try and move to final place now. */
> > -		goto bounce;
> > +		if (!ret)
> > +			/* try and move to final place now. */
> > +			goto bounce;
> As we are at this, can't we replace this with a while()? Goto's
> used instead of a while loop are a fist in the eye...

I'm completely OK with that. this patch already did away with one of 
them. Let's hear Christian's opinion first, though.

Thanks,

Thomas





> It looks even better:
>
> 	while (1) {
> 		ret = ttm_bo_handle_move_mem(bo, evict_mem, true, ctx, &hop);
> 		if (!ret)
> 			break;
>
> 		if (ret == -EMULTIHOP)
> 			ret = ttm_bo_bounce_temp_buffer(bo, &evict_mem,
> 							ctx, &hop);
>
> 		/* try again */
> 		if (!ret)
> 			continue;
>
> 		ttm_resource_free(bo, &evict_mem);
> 		if (ret != -ERESTARTSYS && ret != -EINTR)
> 			pr_err("Buffer eviction failed\n");
>
> 		break;
> 	}
>
> Andi
>
> > +	}
> > +	if (ret) {
> > +		ttm_resource_free(bo, &evict_mem);
> > +		if (ret != -ERESTARTSYS && ret != -EINTR)
> > +			pr_err("Buffer eviction failed\n");
> >   	}
> >   out:
> >   	return ret;
> > --
> > 2.40.1