Re: [PATCH v2] drm: modify drm_global_item_ref to avoid two times of writing ref->object

Sorry, please ignore this V2, there is a typo in "goto out" at this patch. I will send a "update V2" later.

Thanks, Rui

On Wed, Sep 07, 2016 at 11:26:39AM +0800, Huang Rui wrote:

In previous drm_global_item_ref, there are two times of writing ref->object if item->refcount is 0. So this patch does a minor update to put alloc and init ref firstly, and then to modify the item of glob array. Use "else" to avoid two times of writing ref->object. It can make the code logic more clearly.

Signed-off-by: Huang Rui ray.huang@amd.com

Changes from V1 -> V2:

• Add kfree exceptional handle to avoid memory leak.
• Improve code style.

---

drivers/gpu/drm/drm_global.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c index 3d2e91c..6a63808 100644 --- a/drivers/gpu/drm/drm_global.c +++ b/drivers/gpu/drm/drm_global.c @@ -65,30 +65,31 @@ void drm_global_release(void)

int drm_global_item_ref(struct drm_global_reference *ref) {

• int ret;

• int ret = -ENOMEM; struct drm_global_item *item = &glob[ref->global_type];

  mutex_lock(&item->mutex); if (item->refcount == 0) {

• item->object = kzalloc(ref->size, GFP_KERNEL);
  

• if (unlikely(item->object == NULL)) {
  

• 	ret = -ENOMEM;
  

• ref->object = kzalloc(ref->size, GFP_KERNEL);
  

• if (unlikely(ref->object == NULL))
  goto out_err;
  

• }
  

• ref->object = item->object;
  

  ret = ref->init(ref); if (unlikely(ret != 0))

• 	goto out_err;
  

• 	goto out;
  
  

• item->object = ref->object;
  

• } else {

• ref->object = item->object;
  

  }

• ++item->refcount;

• ref->object = item->object;
• mutex_unlock(&item->mutex);
• return 0;

• goto out;

out_err:

• kfree(ref->object);
• ref->object = NULL;

+out: mutex_unlock(&item->mutex);

• item->object = NULL; return ret;

} EXPORT_SYMBOL(drm_global_item_ref); -- 1.9.1