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SubjectRe: [PATCH 03/12] dma-buf: lock the reservation object during (un)map_dma_buf v3
On Tue, Apr 16, 2019 at 08:38:32PM +0200, Christian König wrote:
> Make it mandatory for dynamic dma-buf callbacks to be called with the
> reservation lock held.
>
> For static dma-buf exporters we still have the fallback of using cached sgt.
>
> v2: reordered
> v3: rebased on sgt caching
> v4: use the cached sgt when possible
>
> Signed-off-by: Christian König <christian.koenig@amd.com>

I think there's a bit a rebase chaos going on:
- some comments left behind with no_sgt_cache, which I can't find anymore
- the function signature rework of dma_buf_attach should imo be split out

Next issue is that the reservation object locking is still in the path of
dma_buf_map, so probably still going to result in tons of lockdep splats.
Except the i915+amdgpu path should now work due to the fastpath.

Not sure that's a solution that really works, just hides that
fundamentally we still have that issue of incompatible locking chains
between different drivers.
-Daniel

> ---
> drivers/dma-buf/dma-buf.c | 24 ++++++++++---------
> drivers/gpu/drm/armada/armada_gem.c | 6 ++++-
> drivers/gpu/drm/drm_prime.c | 6 ++++-
> drivers/gpu/drm/i915/i915_gem_dmabuf.c | 6 ++++-
> drivers/gpu/drm/tegra/gem.c | 6 ++++-
> drivers/gpu/drm/udl/udl_dmabuf.c | 6 ++++-
> .../common/videobuf2/videobuf2-dma-contig.c | 6 ++++-
> .../media/common/videobuf2/videobuf2-dma-sg.c | 6 ++++-
> drivers/staging/media/tegra-vde/tegra-vde.c | 6 ++++-
> include/linux/dma-buf.h | 23 ++++++++++++++++--
> 10 files changed, 74 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index ef480e5fb239..83c92bfd964c 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -532,8 +532,9 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> /**
> * dma_buf_attach - Add the device to dma_buf's attachments list; optionally,
> * calls attach() of dma_buf_ops to allow device-specific attach functionality
> - * @dmabuf: [in] buffer to attach device to.
> - * @dev: [in] device to be attached.
> + * @info: [in] holds all the attach related information provided
> + * by the importer. see &struct dma_buf_attach_info
> + * for further details.
> *
> * Returns struct dma_buf_attachment pointer for this attachment. Attachments
> * must be cleaned up by calling dma_buf_detach().
> @@ -547,20 +548,20 @@ EXPORT_SYMBOL_GPL(dma_buf_put);
> * accessible to @dev, and cannot be moved to a more suitable place. This is
> * indicated with the error code -EBUSY.
> */
> -struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> - struct device *dev)
> +struct dma_buf_attachment *dma_buf_attach(const struct dma_buf_attach_info *info)
> {
> + struct dma_buf *dmabuf = info->dmabuf;
> struct dma_buf_attachment *attach;
> int ret;
>
> - if (WARN_ON(!dmabuf || !dev))
> + if (WARN_ON(!dmabuf || !info->dev))
> return ERR_PTR(-EINVAL);
>
> attach = kzalloc(sizeof(*attach), GFP_KERNEL);
> if (!attach)
> return ERR_PTR(-ENOMEM);
>
> - attach->dev = dev;
> + attach->dev = info->dev;
> attach->dmabuf = dmabuf;
>
> mutex_lock(&dmabuf->lock);
> @@ -688,9 +689,9 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach,
> if (attach->sgt)
> return attach->sgt;
>
> - sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
> - if (!sg_table)
> - sg_table = ERR_PTR(-ENOMEM);
> + reservation_object_lock(attach->dmabuf->resv, NULL);
> + sg_table = dma_buf_map_attachment_locked(attach, direction);
> + reservation_object_unlock(attach->dmabuf->resv);
>
> return sg_table;
> }
> @@ -744,8 +745,9 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment *attach,
> if (attach->sgt == sg_table)
> return;
>
> - attach->dmabuf->ops->unmap_dma_buf(attach, sg_table,
> - direction);
> + reservation_object_lock(attach->dmabuf->resv, NULL);
> + dma_buf_unmap_attachment_locked(attach, sg_table, direction);
> + reservation_object_unlock(attach->dmabuf->resv);
> }
> EXPORT_SYMBOL_GPL(dma_buf_unmap_attachment);
>
> diff --git a/drivers/gpu/drm/armada/armada_gem.c b/drivers/gpu/drm/armada/armada_gem.c
> index 642d0e70d0f8..19c47821032f 100644
> --- a/drivers/gpu/drm/armada/armada_gem.c
> +++ b/drivers/gpu/drm/armada/armada_gem.c
> @@ -501,6 +501,10 @@ armada_gem_prime_export(struct drm_device *dev, struct drm_gem_object *obj,
> struct drm_gem_object *
> armada_gem_prime_import(struct drm_device *dev, struct dma_buf *buf)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = dev->dev,
> + .dmabuf = buf
> + };
> struct dma_buf_attachment *attach;
> struct armada_gem_object *dobj;
>
> @@ -516,7 +520,7 @@ armada_gem_prime_import(struct drm_device *dev, struct dma_buf *buf)
> }
> }
>
> - attach = dma_buf_attach(buf, dev->dev);
> + attach = dma_buf_attach(&attach_info);
> if (IS_ERR(attach))
> return ERR_CAST(attach);
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 231e3f6d5f41..1fadf5d5ed33 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -709,6 +709,10 @@ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev,
> struct dma_buf *dma_buf,
> struct device *attach_dev)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = attach_dev,
> + .dmabuf = dma_buf
> + };
> struct dma_buf_attachment *attach;
> struct sg_table *sgt;
> struct drm_gem_object *obj;
> @@ -729,7 +733,7 @@ struct drm_gem_object *drm_gem_prime_import_dev(struct drm_device *dev,
> if (!dev->driver->gem_prime_import_sg_table)
> return ERR_PTR(-EINVAL);
>
> - attach = dma_buf_attach(dma_buf, attach_dev);
> + attach = dma_buf_attach(&attach_info);
> if (IS_ERR(attach))
> return ERR_CAST(attach);
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index 82e2ca17a441..aa7f685bd6ca 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -277,6 +277,10 @@ static const struct drm_i915_gem_object_ops i915_gem_object_dmabuf_ops = {
> struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
> struct dma_buf *dma_buf)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = dev->dev,
> + .dmabuf = dma_buf
> + };
> struct dma_buf_attachment *attach;
> struct drm_i915_gem_object *obj;
> int ret;
> @@ -295,7 +299,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
> }
>
> /* need to attach */
> - attach = dma_buf_attach(dma_buf, dev->dev);
> + attach = dma_buf_attach(&attach_info);
> if (IS_ERR(attach))
> return ERR_CAST(attach);
>
> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
> index 4f80100ff5f3..8e6b6c879add 100644
> --- a/drivers/gpu/drm/tegra/gem.c
> +++ b/drivers/gpu/drm/tegra/gem.c
> @@ -332,6 +332,10 @@ struct tegra_bo *tegra_bo_create_with_handle(struct drm_file *file,
> static struct tegra_bo *tegra_bo_import(struct drm_device *drm,
> struct dma_buf *buf)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = drm->dev,
> + .dmabuf = buf
> + };
> struct tegra_drm *tegra = drm->dev_private;
> struct dma_buf_attachment *attach;
> struct tegra_bo *bo;
> @@ -341,7 +345,7 @@ static struct tegra_bo *tegra_bo_import(struct drm_device *drm,
> if (IS_ERR(bo))
> return bo;
>
> - attach = dma_buf_attach(buf, drm->dev);
> + attach = dma_buf_attach(&attach_info);
> if (IS_ERR(attach)) {
> err = PTR_ERR(attach);
> goto free;
> diff --git a/drivers/gpu/drm/udl/udl_dmabuf.c b/drivers/gpu/drm/udl/udl_dmabuf.c
> index 556f62662aa9..86b928f9742f 100644
> --- a/drivers/gpu/drm/udl/udl_dmabuf.c
> +++ b/drivers/gpu/drm/udl/udl_dmabuf.c
> @@ -226,6 +226,10 @@ static int udl_prime_create(struct drm_device *dev,
> struct drm_gem_object *udl_gem_prime_import(struct drm_device *dev,
> struct dma_buf *dma_buf)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = dev->dev,
> + .dmabuf = dma_buf
> + };
> struct dma_buf_attachment *attach;
> struct sg_table *sg;
> struct udl_gem_object *uobj;
> @@ -233,7 +237,7 @@ struct drm_gem_object *udl_gem_prime_import(struct drm_device *dev,
>
> /* need to attach */
> get_device(dev->dev);
> - attach = dma_buf_attach(dma_buf, dev->dev);
> + attach = dma_buf_attach(&attach_info);
> if (IS_ERR(attach)) {
> put_device(dev->dev);
> return ERR_CAST(attach);
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-contig.c b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> index aff0ab7bf83d..1f2687b5eb0e 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-contig.c
> @@ -676,6 +676,10 @@ static void vb2_dc_detach_dmabuf(void *mem_priv)
> static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
> unsigned long size, enum dma_data_direction dma_dir)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = dev,
> + .dmabuf = dbuf
> + };
> struct vb2_dc_buf *buf;
> struct dma_buf_attachment *dba;
>
> @@ -691,7 +695,7 @@ static void *vb2_dc_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
>
> buf->dev = dev;
> /* create attachment for the dmabuf with the user device */
> - dba = dma_buf_attach(dbuf, buf->dev);
> + dba = dma_buf_attach(&attach_info);
> if (IS_ERR(dba)) {
> pr_err("failed to attach dmabuf\n");
> kfree(buf);
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> index 015e737095cd..cbd626d2393a 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> @@ -608,6 +608,10 @@ static void vb2_dma_sg_detach_dmabuf(void *mem_priv)
> static void *vb2_dma_sg_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
> unsigned long size, enum dma_data_direction dma_dir)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = dev,
> + .dmabuf = dbuf
> + };
> struct vb2_dma_sg_buf *buf;
> struct dma_buf_attachment *dba;
>
> @@ -623,7 +627,7 @@ static void *vb2_dma_sg_attach_dmabuf(struct device *dev, struct dma_buf *dbuf,
>
> buf->dev = dev;
> /* create attachment for the dmabuf with the user device */
> - dba = dma_buf_attach(dbuf, buf->dev);
> + dba = dma_buf_attach(&attach_info);
> if (IS_ERR(dba)) {
> pr_err("failed to attach dmabuf\n");
> kfree(buf);
> diff --git a/drivers/staging/media/tegra-vde/tegra-vde.c b/drivers/staging/media/tegra-vde/tegra-vde.c
> index aa6c6bba961e..5a10c1facc27 100644
> --- a/drivers/staging/media/tegra-vde/tegra-vde.c
> +++ b/drivers/staging/media/tegra-vde/tegra-vde.c
> @@ -568,6 +568,10 @@ static int tegra_vde_attach_dmabuf(struct device *dev,
> size_t *size,
> enum dma_data_direction dma_dir)
> {
> + struct dma_buf_attach_info attach_info = {
> + .dev = dev,
> + .dmabuf = dmabuf
> + };
> struct dma_buf_attachment *attachment;
> struct dma_buf *dmabuf;
> struct sg_table *sgt;
> @@ -591,7 +595,7 @@ static int tegra_vde_attach_dmabuf(struct device *dev,
> return -EINVAL;
> }
>
> - attachment = dma_buf_attach(dmabuf, dev);
> + attachment = dma_buf_attach(&attach_info);
> if (IS_ERR(attachment)) {
> dev_err(dev, "Failed to attach dmabuf\n");
> err = PTR_ERR(attachment);
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index 18a78be53541..7e23758db3a4 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -128,6 +128,9 @@ struct dma_buf_ops {
> * any other kind of sharing that the exporter might wish to make
> * available to buffer-users.
> *
> + * This is always called with the dmabuf->resv object locked when
> + * no_sgt_cache is true.
> + *
> * Returns:
> *
> * A &sg_table scatter list of or the backing storage of the DMA buffer,
> @@ -148,6 +151,9 @@ struct dma_buf_ops {
> * It should also unpin the backing storage if this is the last mapping
> * of the DMA buffer, it the exporter supports backing storage
> * migration.
> + *
> + * This is always called with the dmabuf->resv object locked when
> + * no_sgt_cache is true.
> */
> void (*unmap_dma_buf)(struct dma_buf_attachment *,
> struct sg_table *,
> @@ -370,6 +376,19 @@ struct dma_buf_export_info {
> struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
> .owner = THIS_MODULE }
>
> +/**
> + * struct dma_buf_attach_info - holds information needed to attach to a dma_buf
> + * @dmabuf: the exported dma_buf
> + * @dev: the device which wants to import the attachment
> + *
> + * This structure holds the information required to attach to a buffer. Used
> + * with dma_buf_attach() only.
> + */
> +struct dma_buf_attach_info {
> + struct dma_buf *dmabuf;
> + struct device *dev;
> +};
> +
> /**
> * get_dma_buf - convenience wrapper for get_file.
> * @dmabuf: [in] pointer to dma_buf
> @@ -384,8 +403,8 @@ static inline void get_dma_buf(struct dma_buf *dmabuf)
> get_file(dmabuf->file);
> }
>
> -struct dma_buf_attachment *dma_buf_attach(struct dma_buf *dmabuf,
> - struct device *dev);
> +struct dma_buf_attachment *
> +dma_buf_attach(const struct dma_buf_attach_info *info);
> void dma_buf_detach(struct dma_buf *dmabuf,
> struct dma_buf_attachment *dmabuf_attach);
>
> --
> 2.17.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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