linux-kernel - Re: [PATCH 1/7] drm/shmem-helper: Add lockdep asserts to vmap/vunmap

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Message-ID: <fb7ca812-ad3f-4116-bb58-d34a8bcf979f@amd.com>
Date: Wed, 19 Mar 2025 08:49:33 +0100
From: Christian König <christian.koenig@....com>
To: Daniel Almeida <daniel.almeida@...labora.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>,
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>, Sumit Semwal <sumit.semwal@...aro.org>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org, linux-media@...r.kernel.org,
 linaro-mm-sig@...ts.linaro.org, Danilo Krummrich <dakr@...nel.org>,
 Asahi Lina <lina@...hilina.net>
Subject: Re: [PATCH 1/7] drm/shmem-helper: Add lockdep asserts to vmap/vunmap

Am 18.03.25 um 20:22 schrieb Daniel Almeida:
> From: Asahi Lina <lina@...hilina.net>
>
> Since commit 21aa27ddc582 ("drm/shmem-helper: Switch to reservation
> lock"), the drm_gem_shmem_vmap and drm_gem_shmem_vunmap functions
> require that the caller holds the DMA reservation lock for the object.
> Add lockdep assertions to help validate this.
>
> Signed-off-by: Asahi Lina <lina@...hilina.net>
> Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>

Oh, yeah that is certainly a good idea.

Reviewed-by: Christian König <christian.koenig@....com>

> ---
>  drivers/gpu/drm/drm_gem_shmem_helper.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
> index 5ab351409312b5a0de542df2b636278d6186cb7b..ec89e9499f5f02a2a35713669bf649dd2abb9938 100644
> --- a/drivers/gpu/drm/drm_gem_shmem_helper.c
> +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
> @@ -338,6 +338,8 @@ int drm_gem_shmem_vmap(struct drm_gem_shmem_object *shmem,
>  	struct drm_gem_object *obj = &shmem->base;
>  	int ret = 0;
>  
> +	dma_resv_assert_held(obj->resv);
> +
>  	if (obj->import_attach) {
>  		ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
>  		if (!ret) {
> @@ -404,6 +406,8 @@ void drm_gem_shmem_vunmap(struct drm_gem_shmem_object *shmem,
>  {
>  	struct drm_gem_object *obj = &shmem->base;
>  
> +	dma_resv_assert_held(obj->resv);
> +
>  	if (obj->import_attach) {
>  		dma_buf_vunmap(obj->import_attach->dmabuf, map);
>  	} else {
>