Re: [PATCH 1/4] drm/etnaviv: check for reaped mapping in etnaviv_iommu_unmap_gem

From: "Guido Günther" <agx@sigxcpu.org>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: etnaviv@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	patchwork-lst@pengutronix.de, kernel@pengutronix.de,
	Russell King <linux+etnaviv@armlinux.org.uk>
Subject: Re: [PATCH 1/4] drm/etnaviv: check for reaped mapping in etnaviv_iommu_unmap_gem
Date: Thu, 31 Mar 2022 12:50:54 +0200	[thread overview]
Message-ID: <YkWHjsMFAu/lWFUU@qwark.sigxcpu.org> (raw)
In-Reply-To: <20220323160825.3858619-1-l.stach@pengutronix.de>

Hi Lucas,
On Wed, Mar 23, 2022 at 05:08:22PM +0100, Lucas Stach wrote:
> When the mapping is already reaped the unmap must be a no-op, as we
> would otherwise try to remove the mapping twice, corrupting the involved
> data structures.
> 
> Cc: stable@vger.kernel.org # 5.4
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>

Whole series

Tested-by: Guido Günther <agx@sigxcpu.org>
Acked-by: Guido Günther <agx@sigxcpu.org>

The code changes look good to me too but I got some details wrong too many times
for a `Reviewed-by:`

Cheers,
 -- Guido

> ---
>  drivers/gpu/drm/etnaviv/etnaviv_mmu.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> index 9fb1a2aadbcb..aabb997a74eb 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_mmu.c
> @@ -286,6 +286,12 @@ void etnaviv_iommu_unmap_gem(struct etnaviv_iommu_context *context,
>  
>  	mutex_lock(&context->lock);
>  
> +	/* Bail if the mapping has been reaped by another thread */
> +	if (!mapping->context) {
> +		mutex_unlock(&context->lock);
> +		return;
> +	}
> +
>  	/* If the vram node is on the mm, unmap and remove the node */
>  	if (mapping->vram_node.mm == &context->mm)
>  		etnaviv_iommu_remove_mapping(context, mapping);
> -- 
> 2.30.2
>