Re: [PATCHv3 1/1] RDMA/rxe: Fix a dead lock problem

[Yanjun Zhu <yanjun.zhu@linux.dev>]

在 2022/4/15 0:12, Leon Romanovsky 写道:
> On Thu, Apr 14, 2022 at 11:13:57PM +0800, Yanjun Zhu wrote:
>> 在 2022/4/14 21:52, Jason Gunthorpe 写道:
>>> On Thu, Apr 14, 2022 at 09:01:29PM +0800, Yanjun Zhu wrote:
>>>
>>>>>> Still no, this does almost every allocation - only AH with the
>>>>>> non-blocking flag set should use this path.
>>>
>>>> To the function ib_send_cm_req, the call chain is as below.
>>>>
>>>> ib_send_cm_req --> cm_alloc_priv_msg --> cm_alloc_msg --> rdma_create_ah -->
>>>> _rdma_create_ah --> rxe_create_ah --> rxe_av_chk_attr -->__rxe_add_to_pool
>>>>
>>>> As such, xa_lock_irqsave/irqrestore is selected.
>>>
>>> As I keep saying, only the rxe_create_ah() with the non-blocking flag
>>> set should use the GFP_ATOMIC. All other paths must use GFP_KERNEL.
>>>
>>
>> Got it. The GFP_ATOMIC/GFP_KERNEL are used in different paths.
>> rxe_create_ah will use GFP_ATOMIC and others will use GFP_KERNEL.
>> So the codes should be as below:
>>
>> -int __rxe_add_to_pool(struct rxe_pool *pool, struct rxe_pool_elem *elem)
>> +int __rxe_add_to_pool(struct rxe_pool *pool, struct rxe_pool_elem *elem,
>> gfp_t gfp)
>>   {
>>          int err;
>> +       unsigned long flags;
>>
>>          if (WARN_ON(pool->flags & RXE_POOL_ALLOC))
>>                  return -EINVAL;
>> @@ -168,10 +170,17 @@ int __rxe_add_to_pool(struct rxe_pool *pool, struct
>> rxe_pool_elem *elem)
>>          elem->obj = (u8 *)elem - pool->elem_offset;
>>          kref_init(&elem->ref_cnt);
>>
>> -       xa_lock_irq(&pool->xa);
>> -       err = __xa_alloc_cyclic(&pool->xa, &elem->index, elem, pool->limit,
>> -                               &pool->next, GFP_ATOMIC);
>> -       xa_unlock_irq(&pool->xa);
>> +       if (gfp == GFP_ATOMIC) { /* for rxe_create_ah */
> 
> gfp is bitfield.
> "gfp == GFP_ATOMIC" -> "gfp & GFP_ATOMIC"

Got it. Thanks

Zhu Yanjun

> 
> Thanks