Hi Dawei Li,

On Mon, 21 Nov 2022 at 23:53, Christian König christian.koenig@amd.com wrote:

Hi Dawei,

from the technical description, coding style etc.. it looks clean to me, but I'm the completely wrong person to ask for a background check.

I have a high level understanding of how dma-heaps work, but not a single line of this code is from me.

Feel free to add my Acked-by, but Laura, John and others do you have any opinion?

Regards, Christian.

Am 21.11.22 um 16:28 schrieb Dawei Li:

...

On Sat, Nov 05, 2022 at 12:05:36AM +0800, Dawei Li wrote:

Hi Christian, May I have your opinion on this change?

Thanks, Dawei

...

Racing conflict could be: task A task B list_for_each_entry strcmp(h->name)) list_for_each_entry strcmp(h->name) kzalloc kzalloc ...... ..... device_create device_create list_add list_add

The root cause is that task B has no idea about the fact someone else(A) has inserted heap with same name when it calls list_add, so a potential collision occurs.

Fixes: c02a81fba74f ("dma-buf: Add dma-buf heaps framework") Signed-off-by: Dawei Li set_pte_at@outlook.com

Looks good to me as well. I will apply it over on drm-misc.

Best, Sumit.

...

...

---

v1: https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kerne... v1->v2: Narrow down locking scope, check the existence of heap before insertion, as suggested by Andrew Davis. v2->v3: Remove double checking. v3->v4: Minor coding style and patch formatting adjustment.

---

drivers/dma-buf/dma-heap.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c index 8f5848aa144f..59d158873f4c 100644 --- a/drivers/dma-buf/dma-heap.c +++ b/drivers/dma-buf/dma-heap.c @@ -233,18 +233,6 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) return ERR_PTR(-EINVAL); }

• /* check the name is unique */
• mutex_lock(&heap_list_lock);
• list_for_each_entry(h, &heap_list, list) {

•        if (!strcmp(h->name, exp_info->name)) {
  

•                mutex_unlock(&heap_list_lock);
  

•                pr_err("dma_heap: Already registered heap named %s\n",
  

•                       exp_info->name);
  

•                return ERR_PTR(-EINVAL);
  

•        }
  

• }
• mutex_unlock(&heap_list_lock);
• heap = kzalloc(sizeof(*heap), GFP_KERNEL); if (!heap) return ERR_PTR(-ENOMEM);

@@ -283,13 +271,27 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info) err_ret = ERR_CAST(dev_ret); goto err2; }

• /* Add heap to the list */

• mutex_lock(&heap_list_lock);

• /* check the name is unique */

• list_for_each_entry(h, &heap_list, list) {

•        if (!strcmp(h->name, exp_info->name)) {
  

•                mutex_unlock(&heap_list_lock);
  

•                pr_err("dma_heap: Already registered heap named %s\n",
  

•                       exp_info->name);
  

•                err_ret = ERR_PTR(-EINVAL);
  

•                goto err3;
  

•        }
  

• }

• /* Add heap to the list */ list_add(&heap->list, &heap_list); mutex_unlock(&heap_list_lock);

  return heap;

+err3:

• device_destroy(dma_heap_class, heap->heap_devt); err2: cdev_del(&heap->heap_cdev); err1:

-- 2.25.1