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

2016-09-07 Thread Huang Rui 
On Tue, Sep 06, 2016 at 10:33:18PM +0800, Sean Paul wrote:
> On Mon, Sep 5, 2016 at 3:00 AM, 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 
> > ---
> >  drivers/gpu/drm/drm_global.c | 14 +++---
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c
> > index 3d2e91c..3abe738 100644
> > --- a/drivers/gpu/drm/drm_global.c
> > +++ b/drivers/gpu/drm/drm_global.c
> > @@ -70,25 +70,25 @@ int drm_global_item_ref(struct drm_global_reference 
> > *ref)
> >
> > mutex_lock(>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;
> > }
> > -
> > -   ref->object = item->object;
> > ret = ref->init(ref);
> > if (unlikely(ret != 0))
> > goto out_err;
> >
> > -   }
> > +   item->object = ref->object;
> > +   } else
> > +   ref->object = item->object;
> > +
> 
> You should add the braces to all blocks if they're present in any block.
> 
> > ++item->refcount;
> > -   ref->object = item->object;
> > mutex_unlock(>mutex);
> > return 0;
> >  out_err:
> > mutex_unlock(>mutex);
> > -   item->object = NULL;
> > +   ref->object = NULL;
> 
> It seems like you're leaking memory here. Do you need a
> kfree(ref->object) before this?

Yep, right. The original code seems to missed a kfree exceptional handle.

> 
> I think perhaps you can simplify (or maybe streamline is a better
> word) things better by unifying the unlock and return. Something like:
> 

Thanks, will update it in V2.

Rui

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

2016-09-06 Thread Sean Paul 
On Mon, Sep 5, 2016 at 3:00 AM, 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 
> ---
>  drivers/gpu/drm/drm_global.c | 14 +++---
>  1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c
> index 3d2e91c..3abe738 100644
> --- a/drivers/gpu/drm/drm_global.c
> +++ b/drivers/gpu/drm/drm_global.c
> @@ -70,25 +70,25 @@ int drm_global_item_ref(struct drm_global_reference *ref)
>
> mutex_lock(>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;
> }
> -
> -   ref->object = item->object;
> ret = ref->init(ref);
> if (unlikely(ret != 0))
> goto out_err;
>
> -   }
> +   item->object = ref->object;
> +   } else
> +   ref->object = item->object;
> +

You should add the braces to all blocks if they're present in any block.

> ++item->refcount;
> -   ref->object = item->object;
> mutex_unlock(>mutex);
> return 0;
>  out_err:
> mutex_unlock(>mutex);
> -   item->object = NULL;
> +   ref->object = NULL;

It seems like you're leaking memory here. Do you need a
kfree(ref->object) before this?

I think perhaps you can simplify (or maybe streamline is a better
word) things better by unifying the unlock and return. Something like:


diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c
index 3d2e91c..5b255e4 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 = 0;
struct drm_global_item *item = [ref->global_type];

mutex_lock(>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;
-
+   } else {
+   ref->object = item->object;
}
-   ++item->refcount;
-   ref->object = item->object;
-   mutex_unlock(>mutex);
-   return 0;
+
+   item->refcount++;
+   goto out;
+
 out_err:
+   kfree(ref->object);
+   ref->object = NULL;
+out:
mutex_unlock(>mutex);
-   item->object = NULL;
return ret;
 }
 EXPORT_SYMBOL(drm_global_item_ref);


> return ret;
>  }
>  EXPORT_SYMBOL(drm_global_item_ref);
> --
> 2.7.4
>
> ___
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[PATCH] drm: modify drm_global_item_ref to avoid two times of writing ref->object

2016-09-05 Thread Huang Rui 
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 
---
 drivers/gpu/drm/drm_global.c | 14 +++---
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/drm_global.c b/drivers/gpu/drm/drm_global.c
index 3d2e91c..3abe738 100644
--- a/drivers/gpu/drm/drm_global.c
+++ b/drivers/gpu/drm/drm_global.c
@@ -70,25 +70,25 @@ int drm_global_item_ref(struct drm_global_reference *ref)

mutex_lock(>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;
}
-
-   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(>mutex);
return 0;
 out_err:
mutex_unlock(>mutex);
-   item->object = NULL;
+   ref->object = NULL;
return ret;
 }
 EXPORT_SYMBOL(drm_global_item_ref);
-- 
2.7.4