linux-kernel - Re: [PATCH] drm/msm/gpu: Don't allow zero fence

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Date:   Mon, 29 Nov 2021 13:02:05 -0800
From:   Rob Clark <robdclark@...il.com>
To:     dri-devel <dri-devel@...ts.freedesktop.org>
Cc:     freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...omium.org>,
        Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/gpu: Don't allow zero fence_id

On Mon, Nov 29, 2021 at 10:18 AM Rob Clark <robdclark@...il.com> wrote:
>
> From: Rob Clark <robdclark@...omium.org>
>
> Elsewhere we treat zero as "no fence" and __msm_gem_submit_destroy()
> skips removal from fence_idr.  We could alternately change this to use
> negative values for "no fence" but I think it is more clear to not allow
> zero as a valid fence_id.
>

probably should have added:

Fixes: a61acbbe9cf8 ("drm/msm: Track "seqno" fences by idr")

> Signed-off-by: Rob Clark <robdclark@...omium.org>
> ---
>  drivers/gpu/drm/msm/msm_gem_submit.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/msm_gem_submit.c b/drivers/gpu/drm/msm/msm_gem_submit.c
> index 282628d6b72c..6cfa984dee6a 100644
> --- a/drivers/gpu/drm/msm/msm_gem_submit.c
> +++ b/drivers/gpu/drm/msm/msm_gem_submit.c
> @@ -881,7 +881,7 @@ int msm_ioctl_gem_submit(struct drm_device *dev, void *data,
>          * to the underlying fence.
>          */
>         submit->fence_id = idr_alloc_cyclic(&queue->fence_idr,
> -                       submit->user_fence, 0, INT_MAX, GFP_KERNEL);
> +                       submit->user_fence, 1, INT_MAX, GFP_KERNEL);
>         if (submit->fence_id < 0) {
>                 ret = submit->fence_id = 0;
>                 submit->fence_id = 0;
> --
> 2.33.1
>