[PATCH] drm/prime: keep a reference from the handle to exported dma-buf (v4)
Daniel Vetter
daniel at ffwll.ch
Wed Apr 17 01:21:13 PDT 2013
On Wed, Apr 17, 2013 at 02:38:02PM +1000, Dave Airlie wrote:
> Currently we have a problem with this:
> 1. i915: create gem object
> 2. i915: export gem object to prime
> 3. radeon: import gem object
> 4. close prime fd
> 5. radeon: unref object
> 6. i915: unref object
>
> i915 has an imported object reference in its file priv, that isn't
> cleaned up properly until fd close. The reference gets added at step 2,
> but at step 6 we don't have enough info to clean it up.
>
> The solution is to take a reference on the dma-buf when we export it,
> and drop the reference when the gem handle goes away.
>
> So when we export a dma_buf from a gem object, we keep track of it
> with the handle, we take a reference to the dma_buf. When we close
> the handle (i.e. userspace is finished with the buffer), we drop
> the reference to the dma_buf, and it gets collected.
>
> This patch isn't meant to fix any other problem or bikesheds, and it doesn't
> fix any races with other scenarios.
>
> v1.1: move export symbol line back up.
>
> v2: okay I had to do a bit more, as the first patch showed a leak
> on one of my tests, that I found using the dma-buf debugfs support,
> the problem case is exporting a buffer twice with the same handle,
> we'd add another export handle for it unnecessarily, however
> we now fail if we try to export the same object with a different gem handle,
> however I'm not sure if that is a case I want to support, and I've
> gotten the code to WARN_ON if we hit something like that.
>
> v2.1: rebase this patch, write better commit msg.
> v3: cleanup error handling, track import vs export in linked list,
> these two patches were separate previously, but seem to work better
> like this.
> v4: danvet is correct, this code is no longer useful, since the buffer
> better exist, so remove it.
>
> Signed-off-by: Dave Airlie <airlied at redhat.com>
Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
On bikeshed review level I wonder whether we shouldn't just grab a
reference unconditonally when inserting it into the handle_to_fd lookup
lists. But I need to think through a few other cases and apparently the
self-import test is still a bit broken. So this is material for follow-up
patches.
-Daniel
> ---
> drivers/gpu/drm/drm_gem.c | 4 +-
> drivers/gpu/drm/drm_prime.c | 95 +++++++++++++++++++++++++++++----------------
> include/drm/drmP.h | 4 +-
> 3 files changed, 65 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
> index af779ae..cf919e3 100644
> --- a/drivers/gpu/drm/drm_gem.c
> +++ b/drivers/gpu/drm/drm_gem.c
> @@ -205,11 +205,11 @@ static void
> drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct drm_file *filp)
> {
> if (obj->import_attach) {
> - drm_prime_remove_imported_buf_handle(&filp->prime,
> + drm_prime_remove_buf_handle(&filp->prime,
> obj->import_attach->dmabuf);
> }
> if (obj->export_dma_buf) {
> - drm_prime_remove_imported_buf_handle(&filp->prime,
> + drm_prime_remove_buf_handle(&filp->prime,
> obj->export_dma_buf);
> }
> }
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 366910d..b4ed808 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -57,10 +57,14 @@
> * use the drm_gem_prime_{import,export} helpers.
> */
>
> +#define PRIME_IMPORT 1
> +#define PRIME_EXPORT 2
> +
> struct drm_prime_member {
> struct list_head entry;
> struct dma_buf *dma_buf;
> uint32_t handle;
> + int type;
> };
>
> static struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach,
> @@ -157,6 +161,8 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops = {
> .vunmap = drm_gem_dmabuf_vunmap,
> };
>
> +static int drm_prime_add_exported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle);
> +
> /**
> * DOC: PRIME Helpers
> *
> @@ -200,7 +206,9 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
> {
> struct drm_gem_object *obj;
> void *buf;
> - int ret;
> + int ret = 0;
> + struct dma_buf *dmabuf;
> + uint32_t exp_handle;
>
> obj = drm_gem_object_lookup(dev, file_priv, handle);
> if (!obj)
> @@ -209,43 +217,44 @@ int drm_gem_prime_handle_to_fd(struct drm_device *dev,
> mutex_lock(&file_priv->prime.lock);
> /* re-export the original imported object */
> if (obj->import_attach) {
> - get_dma_buf(obj->import_attach->dmabuf);
> - *prime_fd = dma_buf_fd(obj->import_attach->dmabuf, flags);
> - drm_gem_object_unreference_unlocked(obj);
> - mutex_unlock(&file_priv->prime.lock);
> - return 0;
> + dmabuf = obj->import_attach->dmabuf;
> + goto out_have_obj;
> }
>
> if (obj->export_dma_buf) {
> - get_dma_buf(obj->export_dma_buf);
> - *prime_fd = dma_buf_fd(obj->export_dma_buf, flags);
> - drm_gem_object_unreference_unlocked(obj);
> - } else {
> - buf = dev->driver->gem_prime_export(dev, obj, flags);
> - if (IS_ERR(buf)) {
> - /* normally the created dma-buf takes ownership of the ref,
> - * but if that fails then drop the ref
> - */
> - drm_gem_object_unreference_unlocked(obj);
> - mutex_unlock(&file_priv->prime.lock);
> - return PTR_ERR(buf);
> - }
> - obj->export_dma_buf = buf;
> - *prime_fd = dma_buf_fd(buf, flags);
> + dmabuf = obj->export_dma_buf;
> + goto out_have_obj;
> + }
> +
> + buf = dev->driver->gem_prime_export(dev, obj, flags);
> + if (IS_ERR(buf)) {
> + /* normally the created dma-buf takes ownership of the ref,
> + * but if that fails then drop the ref
> + */
> + ret = PTR_ERR(buf);
> + goto out;
> }
> + obj->export_dma_buf = buf;
> +
> /* if we've exported this buffer the cheat and add it to the import list
> * so we get the correct handle back
> */
> - ret = drm_prime_add_imported_buf_handle(&file_priv->prime,
> - obj->export_dma_buf, handle);
> - if (ret) {
> - drm_gem_object_unreference_unlocked(obj);
> - mutex_unlock(&file_priv->prime.lock);
> - return ret;
> - }
> + ret = drm_prime_add_exported_buf_handle(&file_priv->prime,
> + obj->export_dma_buf, handle);
> + if (ret)
> + goto out;
>
> + *prime_fd = dma_buf_fd(buf, flags);
> mutex_unlock(&file_priv->prime.lock);
> return 0;
> +
> +out_have_obj:
> + get_dma_buf(dmabuf);
> + *prime_fd = dma_buf_fd(dmabuf, flags);
> +out:
> + drm_gem_object_unreference_unlocked(obj);
> + mutex_unlock(&file_priv->prime.lock);
> + return ret;
> }
> EXPORT_SYMBOL(drm_gem_prime_handle_to_fd);
>
> @@ -314,7 +323,7 @@ int drm_gem_prime_fd_to_handle(struct drm_device *dev,
>
> mutex_lock(&file_priv->prime.lock);
>
> - ret = drm_prime_lookup_imported_buf_handle(&file_priv->prime,
> + ret = drm_prime_lookup_buf_handle(&file_priv->prime,
> dma_buf, handle);
> if (!ret) {
> ret = 0;
> @@ -491,7 +500,7 @@ void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv)
> }
> EXPORT_SYMBOL(drm_prime_destroy_file_private);
>
> -int drm_prime_add_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle)
> +static int drm_prime_add_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle, int type)
> {
> struct drm_prime_member *member;
>
> @@ -501,12 +510,25 @@ int drm_prime_add_imported_buf_handle(struct drm_prime_file_private *prime_fpriv
>
> member->dma_buf = dma_buf;
> member->handle = handle;
> + member->type = type;
> list_add(&member->entry, &prime_fpriv->head);
> return 0;
> }
> +
> +int drm_prime_add_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle)
> +{
> + return drm_prime_add_buf_handle(prime_fpriv, dma_buf, handle, PRIME_IMPORT);
> +}
> EXPORT_SYMBOL(drm_prime_add_imported_buf_handle);
>
> -int drm_prime_lookup_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t *handle)
> +static int drm_prime_add_exported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle)
> +{
> + /* take a reference to the buf handle for this case */
> + get_dma_buf(dma_buf);
> + return drm_prime_add_buf_handle(prime_fpriv, dma_buf, handle, PRIME_EXPORT);
> +}
> +
> +int drm_prime_lookup_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t *handle)
> {
> struct drm_prime_member *member;
>
> @@ -518,19 +540,24 @@ int drm_prime_lookup_imported_buf_handle(struct drm_prime_file_private *prime_fp
> }
> return -ENOENT;
> }
> -EXPORT_SYMBOL(drm_prime_lookup_imported_buf_handle);
> +EXPORT_SYMBOL(drm_prime_lookup_buf_handle);
>
> -void drm_prime_remove_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf)
> +void drm_prime_remove_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf)
> {
> struct drm_prime_member *member, *safe;
>
> mutex_lock(&prime_fpriv->lock);
> list_for_each_entry_safe(member, safe, &prime_fpriv->head, entry) {
> if (member->dma_buf == dma_buf) {
> + if (member->type == PRIME_EXPORT)
> + dma_buf_put(dma_buf);
> list_del(&member->entry);
> kfree(member);
> }
> }
> mutex_unlock(&prime_fpriv->lock);
> }
> -EXPORT_SYMBOL(drm_prime_remove_imported_buf_handle);
> +EXPORT_SYMBOL(drm_prime_remove_buf_handle);
> +
> +
> +
> diff --git a/include/drm/drmP.h b/include/drm/drmP.h
> index 2d94d74..69712a6 100644
> --- a/include/drm/drmP.h
> +++ b/include/drm/drmP.h
> @@ -1594,8 +1594,8 @@ extern void drm_prime_gem_destroy(struct drm_gem_object *obj, struct sg_table *s
> void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv);
> void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv);
> int drm_prime_add_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t handle);
> -int drm_prime_lookup_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t *handle);
> -void drm_prime_remove_imported_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf);
> +int drm_prime_lookup_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf, uint32_t *handle);
> +void drm_prime_remove_buf_handle(struct drm_prime_file_private *prime_fpriv, struct dma_buf *dma_buf);
>
> int drm_prime_add_dma_buf(struct drm_device *dev, struct drm_gem_object *obj);
> int drm_prime_lookup_obj(struct drm_device *dev, struct dma_buf *buf,
> --
> 1.8.2
>
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--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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