linux-kernel - Re: [PATCH v1, 1/1] drm/mediatek: fixup crtc event null pointer issue

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Message-ID: <9f14d6a0aa782a8f6c3e7044fe90d74b80d17ed0.camel@mediatek.com>
Date:   Mon, 28 Mar 2022 17:34:51 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Yongqiang Niu <yongqiang.niu@...iatek.com>,
        Chun-Kuang Hu <chunkuang.hu@...nel.org>
CC:     <devicetree@...r.kernel.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>,
        David Airlie <airlied@...ux.ie>,
        Jassi Brar <jassisinghbrar@...il.com>,
        <linux-kernel@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        "Dennis YC Hsieh" <dennis-yc.hsieh@...iatek.com>,
        Fabien Parent <fparent@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        <linux-mediatek@...ts.infradead.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v1, 1/1] drm/mediatek: fixup crtc event null pointer
 issue

Hi, Yongqiang:

On Mon, 2022-03-14 at 15:42 +0800, Yongqiang Niu wrote:
> if crtc event is null pointer, do not send vblank event

This is a bug-fix, so add a Fixes tag here.

> 
> Signed-off-by: Yongqiang Niu <yongqiang.niu@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index d661edf7e0fe..265fed446628 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -92,6 +92,9 @@ static void mtk_drm_crtc_finish_page_flip(struct
> mtk_drm_crtc *mtk_crtc)
>  	struct drm_crtc *crtc = &mtk_crtc->base;
>  	unsigned long flags;
>  
> +	if (!mtk_crtc->event)
> +		return;
> +
>  	spin_lock_irqsave(&crtc->dev->event_lock, flags);
>  	drm_crtc_send_vblank_event(crtc, mtk_crtc->event);

I think pending_needs_vblank is used to protect this situation. It
seems that pending_needs_vblank should be protected by critical
section.

Regards,
CK

>  	drm_crtc_vblank_put(crtc);