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. v5: always take a reference to the dma buf object, import or export. (Imre Deak contributed this originally) v6: square the circle, remove import vs export tracking now that there is no difference

Signed-off-by: Dave Airlie airlied@redhat.com --- drivers/gpu/drm/drm_gem.c | 4 +-- drivers/gpu/drm/drm_prime.c | 76 ++++++++++++++++++++++++--------------------- include/drm/drmP.h | 5 ++- 3 files changed, 44 insertions(+), 41 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..fd029dc 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -62,6 +62,7 @@ struct drm_prime_member { 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);

static struct sg_table *drm_gem_map_dma_buf(struct dma_buf_attachment *attach, enum dma_data_direction dir) @@ -200,7 +201,8 @@ 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;

obj = drm_gem_object_lookup(dev, file_priv, handle); if (!obj) @@ -209,43 +211,44 @@ 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_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 +317,7 @@ 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; @@ -333,7 +336,7 @@ int drm_gem_prime_fd_to_handle(struct drm_device *dev, if (ret) goto out_put;

- ret = drm_prime_add_imported_buf_handle(&file_priv->prime, + ret = drm_prime_add_buf_handle(&file_priv->prime, dma_buf, *handle); if (ret) goto fail; @@ -491,7 +494,7 @@ 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) { struct drm_prime_member *member;

@@ -499,14 +502,14 @@ int drm_prime_add_imported_buf_handle(struct drm_prime_file_private *prime_fpriv if (!member) return -ENOMEM;

+ get_dma_buf(dma_buf); member->dma_buf = dma_buf; member->handle = handle; list_add(&member->entry, &prime_fpriv->head); return 0; } -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) +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 +521,20 @@ 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) { + 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..f1ce786 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -1593,9 +1593,8 @@ 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,