[PATCH] drm/etnaviv: lock MMU while dumping core

[Russell King - ARM Linux admin]

Hi Lucas,

Seems I'm not getting a reply, so I'm hijacking one of your more
recent patches in the hope of attracting your attention.

A while back I sent a fix for a regression that recently occurred
with etnaviv, where the kernel spat out a warning when importing
buffers into etnaviv.  You apparently merged this as "development",
queuing it up for the last merge window.

Since it is a regression (although not directly attributable to
etnaviv), please ensure that it is merged into stable kernels.

Thanks.

On Wed, May 22, 2019 at 11:55:14AM +0200, Lucas Stach wrote:
> The devcoredump needs to operate on a stable state of the MMU while
> it is writing the MMU state to the coredump. The missing lock
> allowed both the userspace submit, as well as the GPU job finish
> paths to mutate the MMU state while a coredump is under way.
> 
> Fixes: a8c21a5451d8 (drm/etnaviv: add initial etnaviv DRM driver)
> Reported-by: David Jander <david at protonic.nl>
> Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
> Tested-by: David Jander <david at protonic.nl>
> ---
>  drivers/gpu/drm/etnaviv/etnaviv_dump.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/gpu/drm/etnaviv/etnaviv_dump.c b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
> index 33854c94cb85..515515ef24f9 100644
> --- a/drivers/gpu/drm/etnaviv/etnaviv_dump.c
> +++ b/drivers/gpu/drm/etnaviv/etnaviv_dump.c
> @@ -125,6 +125,8 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
>  		return;
>  	etnaviv_dump_core = false;
>  
> +	mutex_lock(&gpu->mmu->lock);
> +
>  	mmu_size = etnaviv_iommu_dump_size(gpu->mmu);
>  
>  	/* We always dump registers, mmu, ring and end marker */
> @@ -167,6 +169,7 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
>  	iter.start = __vmalloc(file_size, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY,
>  			       PAGE_KERNEL);
>  	if (!iter.start) {
> +		mutex_unlock(&gpu->mmu->lock);
>  		dev_warn(gpu->dev, "failed to allocate devcoredump file\n");
>  		return;
>  	}
> @@ -234,6 +237,8 @@ void etnaviv_core_dump(struct etnaviv_gpu *gpu)
>  					 obj->base.size);
>  	}
>  
> +	mutex_unlock(&gpu->mmu->lock);
> +
>  	etnaviv_core_dump_header(&iter, ETDUMP_BUF_END, iter.data);
>  
>  	dev_coredumpv(gpu->dev, iter.start, iter.data - iter.start, GFP_KERNEL);
> -- 
> 2.20.1
> 
> 

-- 
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