Am 17.06.2017 um 00:00 schrieb axie:
On 2017-06-16 01:48 PM, Christian König wrote:
Am 16.06.2017 um 07:03 schrieb Alex Xie:
Use rw_semaphore instead of mutex for bo_lists.
In original function amdgpu_bo_list_get, the waiting
for result->lock can be quite long while mutex
bo_list_lock was holding. It can make other tasks
waiting for bo_list_lock for long period too.
Change bo_list_lock to rw_semaphore can avoid most of
such long waiting.
Secondly, this patch allows several tasks(readers of idr)
to proceed at the same time.
v2: use rcu and kref (Dave Airlie and Christian König)
Signed-off-by: Alex Xie <[email protected]>
---
drivers/gpu/drm/amd/amdgpu/amdgpu.h | 2 ++
drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c | 40
++++++++++++++++++++---------
2 files changed, 30 insertions(+), 12 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 063fc73..e9b3981 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -871,6 +871,8 @@ struct amdgpu_fpriv {
struct amdgpu_bo_list {
struct mutex lock;
+ struct rcu_head rhead;
+ struct kref refcount;
struct amdgpu_bo *gds_obj;
struct amdgpu_bo *gws_obj;
struct amdgpu_bo *oa_obj;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
index 5af956f..efa6903 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_bo_list.c
@@ -41,6 +41,20 @@ static int amdgpu_bo_list_set(struct
amdgpu_device *adev,
struct drm_amdgpu_bo_list_entry *info,
unsigned num_entries);
+static void amdgpu_bo_list_release_rcu(struct kref *ref)
+{
+ unsigned i;
+ struct amdgpu_bo_list *list = container_of(ref, struct
amdgpu_bo_list,
+ refcount);
+
+ for (i = 0; i < list->num_entries; ++i)
+ amdgpu_bo_unref(&list->array[i].robj);
+
+ mutex_destroy(&list->lock);
+ drm_free_large(list->array);
+ kfree_rcu(list, rhead);
+}
+
I'm probably missing something here: Why a new function and not
change the existing amdgpu_bo_list_free() to use kfree_rcu instead?
Apart from that the patch looks good to me,
Christian.
amdgpu_bo_list_free() is called by amdgpu_driver_postclose_kms in file
amdgpu_kms.c too.
For amdgpu_driver_postclose_kms, there is no need to call kfree_rcu.
It is more suitable to call kfree.
So we need two different release/free functions. Then I created a new
function for kref_put.
Ah, I see. Well call from amdgpu_driver_postclose_kms() is only used
when the application crashes and doesn't clean up properly after itself.
Not sure if it's a good idea to duplicate the code because of this.
Waiting for an RCU grace period is a no-op in most cases (it's very
likely that all other CPUs are doing something in userspace), so
kfree_rcu is rather cheap.
Either way the patch is Reviewed-by: Christian König
<[email protected]>.
static int amdgpu_bo_list_create(struct amdgpu_device *adev,
struct drm_file *filp,
struct drm_amdgpu_bo_list_entry *info,
@@ -57,7 +71,7 @@ static int amdgpu_bo_list_create(struct
amdgpu_device *adev,
/* initialize bo list*/
mutex_init(&list->lock);
-
+ kref_init(&list->refcount);
r = amdgpu_bo_list_set(adev, filp, list, info, num_entries);
if (r) {
kfree(list);
@@ -83,14 +97,9 @@ static void amdgpu_bo_list_destroy(struct
amdgpu_fpriv *fpriv, int id)
mutex_lock(&fpriv->bo_list_lock);
list = idr_remove(&fpriv->bo_list_handles, id);
- if (list) {
- /* Another user may have a reference to this list still */
- mutex_lock(&list->lock);
- mutex_unlock(&list->lock);
- amdgpu_bo_list_free(list);
- }
-
mutex_unlock(&fpriv->bo_list_lock);
+ if (list)
+ kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
}
static int amdgpu_bo_list_set(struct amdgpu_device *adev,
@@ -185,11 +194,17 @@ amdgpu_bo_list_get(struct amdgpu_fpriv *fpriv,
int id)
{
struct amdgpu_bo_list *result;
- mutex_lock(&fpriv->bo_list_lock);
+ rcu_read_lock();
result = idr_find(&fpriv->bo_list_handles, id);
- if (result)
- mutex_lock(&result->lock);
- mutex_unlock(&fpriv->bo_list_lock);
+
+ if (result) {
+ if (kref_get_unless_zero(&result->refcount))
+ mutex_lock(&result->lock);
+ else
+ result = NULL;
+ }
+ rcu_read_unlock();
+
return result;
}
@@ -227,6 +242,7 @@ void amdgpu_bo_list_get_list(struct
amdgpu_bo_list *list,
void amdgpu_bo_list_put(struct amdgpu_bo_list *list)
{
mutex_unlock(&list->lock);
+ kref_put(&list->refcount, amdgpu_bo_list_release_rcu);
}
void amdgpu_bo_list_free(struct amdgpu_bo_list *list)
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