Am 07.09.2016 um 09:54 schrieb Huang Rui:

On Wed, Sep 07, 2016 at 09:12:29AM +0200, Christian König wrote:

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Am 07.09.2016 um 07:24 schrieb Huang Rui:

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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

Well when you update your patch, even when it's just fixing a small typo, please increase the version number.

That makes it much easier to track the different instances of a patch.

OK.

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A few additional notes below.

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Changes from V1 -> V2:

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

---

drivers/gpu/drm/drm_global.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c index 3d2e91c..b181e81 100644 --- a/drivers/gpu/drm/drm_global.c +++ b/drivers/gpu/drm/drm_global.c @@ -65,30 +65,33 @@ void drm_global_release(void) int drm_global_item_ref(struct drm_global_reference *ref) {

• int ret;

• int ret = 0; 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)) {
  

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

• if (unlikely(ref->object == NULL)) {
  ret = -ENOMEM;
  

• 	goto out_err;
  

• 	goto out;
  

  }

• ref->object = item->object;
  

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

• item->object = ref->object;
  

• } else {

• ref->object = item->object;
  

  }
• ++item->refcount;

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

• goto out;

A goto in the not error path is a bit unusual. Since out_err is only used once couldn't you just move the code into the if and then goto to out as well?

Alternative you could just duplicate the mutex release in the non-error path.

Actually, I also have a little concern with "goto" in non-error path. But as Sean's suggestion, use "goto" can avoid a duplicate mutex release, you know.

I would certainly prefer the duplicate mutex release.

@Sean, if you don't have concern with adding a mutex release below, I will update it in V3.

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     ++item->refcount;
     mutex_unlock(&item->mutex);
     return 0;

out_err: kfree(ref->object); ref->object = NULL; out:

BTW: I would name those labels error_free and error_unlock to make clear that they are for error handling and what they are supposed to do.

Regards, Christian.

     mutex_unlock(&item->mutex);
     return ret;

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Thanks, Rui