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SubjectRe: [PATCH 03/12] dma-buf: lock the reservation object during (un)map_dma_buf v3
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Am 17.04.19 um 16:08 schrieb Daniel Vetter:
> 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

Ah, crap thought I've got all of those. Going to fix that.

> 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.

I actually found a solution for that :)

The idea is now that we always cache the sgt in the attachment unless
the dynamic flag (previously no_sgt_cache flag) is set. And this cached
sgt is created without holding the lock.

We either need to document that really well or maybe split the mapping
callbacks into map/unmap and map_lock/unmap_locked. Opinions?

>
> 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.

We can now make a slow transition between static and dynamic DMA-buf
handling, so only driver who can do the locking will be affected.

Christian.

> -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

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