[ 108/136 ] drm/prime: keep a reference from the handle to exported dma-buf (v6)

Steven Rostedt
2013-05-18T03:13:10Z

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3.6.11.4 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Dave Airlie <airlied@gmail.com>

[ Upstream commit 219b47339ced80ca580bb6ce7d1636166984afa7 ]

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

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
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 fbe0842..730b93f 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 f546ff9..6497c53 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -61,6 +61,7 @@ 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);

int drm_gem_prime_handle_to_fd(struct drm_device *dev,
struct drm_file *file_priv, uint32_t handle, uint32_t flags,
@@ -68,7 +69,8 @@ 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)
@@ -77,43 +79,44 @@ 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);

@@ -130,7 +133,7 @@ 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;
@@ -149,7 +152,7 @@ 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;
@@ -307,7 +310,7 @@ 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;

@@ -315,14 +318,14 @@ 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;

@@ -334,19 +337,20 @@ 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 d6b67bb..efd9db4 100644
--- a/include/drm/drmP.h
+++ b/include/drm/drmP.h
@@ -1554,9 +1554,8 @@ 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,
--
1.7.10.4