Re: [PATCH for-next 2/3] RDMA/rtrs: Fix rxe_dealloc_pd warning
From: Zhijian Li (Fujitsu)
Date: Tue Apr 18 2023 - 02:49:07 EST
On 17/04/2023 11:08, Guoqing Jiang wrote:
>
>
> On 4/14/23 18:09, Zhijian Li (Fujitsu) wrote:
>>
>> On 14/04/2023 14:04, Guoqing Jiang wrote:
>>>
>>> On 4/14/23 13:37, Zhijian Li (Fujitsu) wrote:
>>>> On 14/04/2023 11:40, Guoqing Jiang wrote:
>>>>> On 4/13/23 16:12, Zhijian Li (Fujitsu) wrote:
>>>>>> On 13/04/2023 15:35, Guoqing Jiang wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I take a closer look today.
>>>>>>>
>>>>>>> On 4/12/23 09:15, Zhijian Li (Fujitsu) wrote:
>>>>>>>> On 11/04/2023 20:26, Leon Romanovsky wrote:
>>>>>>>>> On Tue, Apr 11, 2023 at 02:43:46AM +0000, Zhijian Li (Fujitsu) wrote:
>>>>>>>>>> On 10/04/2023 21:10, Guoqing Jiang wrote:
>>>>>>>>>>> On 4/10/23 20:08, Leon Romanovsky wrote:
>>>>>>>>>>>> On Mon, Apr 10, 2023 at 06:43:03AM +0000, Li Zhijian wrote:
>>>>>>>>>>>>> The warning occurs when destroying PD whose reference count is not zero.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Precodition: clt_path->s.con_num is 2.
>>>>>>>>>>>>> So 2 cm connection will be created as below:
>>>>>>>>>>>>> CPU0 CPU1
>>>>>>>>>>>>> init_conns { |
>>>>>>>>>>>>> create_cm() // a. con[0] created |
>>>>>>>>>>>>> | a'. rtrs_clt_rdma_cm_handler() {
>>>>>>>>>>>>> | rtrs_rdma_addr_resolved()
>>>>>>>>>>>>> | create_con_cq_qp(con); << con[0]
>>>>>>>>>>>>> | }
>>>>>>>>>>>>> | in this moment, refcnt of PD was increased to 2+
>>>>>>> What do you mean "refcnt of PD"? usecnt in struct ib_pd or dev_ref.
>>>>>> I mean usecnt in struct ib_pd
>>>>>>
>>>>>>>>>>>>> |
>>>>>>>>>>>>> create_cm() // b. cid = 1, failed |
>>>>>>>>>>>>> destroy_con_cq_qp() |
>>>>>>>>>>>>> rtrs_ib_dev_put() |
>>>>>>>>>>>>> dev_free() |
>>>>>>>>>>>>> ib_dealloc_pd(dev->ib_pd) << PD |
>>>>>>>>>>>>> is destroyed, but refcnt is |
>>>>>>>>>>>>> still greater than 0 |
>>>>>>> Assuming you mean "pd->usecnt". We only allocate pd in con[0] by rtrs_ib_dev_find_or_add,
>>>>>>> if con[1] failed to create cm, then alloc_path_reqs -> ib_alloc_mr -> atomic_inc(&pd->usecnt)
>>>>> The above can't be invoked, right?
>>>>>
>>>>>>> can't be triggered. Is there other places could increase the refcnt?
>>>>>> Yes, when create a qp, it will also associate to this PD, that also mean refcnt of PD will be increased.
>>>>>>
>>>>>> When con[0](create_con_cq_qp) succeeded, refcnt of PD will be 2. and then when con[1] failed, since
>>>>>> QP didn't create, refcnt of PD is still 2. con[1]'s cleanup will destroy the PD(ib_dealloc_pd) since dev_ref = 1, after that its
>>>>>> refcnt is still 1.
>>>>> I can see the path increase usecnt to 1.
>>>>>
>>>>> rtrs_cq_qp_create -> create_qp
>>>>> -> rdma_create_qp
>>>>> -> ib_create_qp
>>>>> -> create_qp
>>>>> -> ib_qp_usecnt_inc which increases pd->usecnt
>>>>>
>>>>> Where is another place to increase usecnt to 2?
>>>> It should be
>>>> ib_create_qp ...
>>>> -> rxe_create_qp
>>>> -> rxe_qp_from_init
>>>> -> rxe_get(pd) <<< pd's refcnt will be increased.
>>> Isn't rxe_get just increase elem->ref_cnt?
>> Yes, that's true.
>
> I am confused, does increase ref_cnt equal to increase usecnt?
I need to apologize for my mistake. I have been referring to the elem.ref_cnt of the rxe driver as the refcnt of PD.
> If not, then where is another place to increase usecnt to 2?
>
> BTW, I traced with 6.3-rc5, seems pd's usecnt is only increase once
> after create one connection.
And the warning mentioned above it also pointed to the PD's elem.ref_cnt.
>
> [ 6941.525088] in init_conns 2353 con_num=3
> [ 6941.525732] in create_con_cq_qp 1648
> [ 6941.525944] in rtrs_cq_qp_create 311 con->cid=0 path->dev->ib_pd->usecnt=1
> [ 6941.532460] in create_con_cq_qp 1648
> [ 6941.532746] in rtrs_cq_qp_create 311 con->cid=1 path->dev->ib_pd->usecnt=2
> [ 6941.533183] in create_con_cq_qp 1648
> [ 6941.533464] in rtrs_cq_qp_create 311 con->cid=2 path->dev->ib_pd->usecnt=3
> [ 6941.533685] in init_conns 2365, clt_path->s.dev->ib_pd->usecnt=3
> [ 6941.535680] in init_conns 2371, clt_path->s.dev->ib_pd->usecnt=515
Thanks
Zhijian
below is a piece of code that i used to debug this issue.
--- a/drivers/infiniband/ulp/rtrs/rtrs-clt.c
+++ b/drivers/infiniband/ulp/rtrs/rtrs-clt.c
@@ -1730,15 +1730,39 @@ static int create_con_cq_qp(struct rtrs_clt_con *con)
return err;
}
+struct rxe_pool;
+struct rxe_pool_elem {
+ struct rxe_pool *pool;
+ void *obj;
+ struct kref ref_cnt;
+ struct list_head list;
+ struct completion complete;
+ u32 index;
+};
+
+struct rxe_pd {
+ struct ib_pd ibpd;
+ struct rxe_pool_elem elem;
+};
+
+static inline struct rxe_pd *to_rpd(struct ib_pd *pd)
+{
+ return pd ? container_of(pd, struct rxe_pd, ibpd) : NULL;
+}
+
+#define rxe_read(obj) kref_read(&(obj)->elem.ref_cnt)
static void destroy_con_cq_qp(struct rtrs_clt_con *con)
{
struct rtrs_clt_path *clt_path = to_clt_path(con->c.path);
+ struct rtrs_ib_dev *dev = clt_path->s.dev;
+ struct rxe_pd *pd = to_rpd(dev->ib_pd);
/*
* Be careful here: destroy_con_cq_qp() can be called even
* create_con_cq_qp() failed, see comments there.
*/
lockdep_assert_held(&con->con_mutex);
+ rtrs_info(clt_path->clt, "%s: clt_path->s.dev_ref: %d, pd %px, ref: %d\n", __func__, clt_path->s.dev_ref, &pd->elem, rxe_read(pd));
rtrs_cq_qp_destroy(&con->c);
if (con->rsp_ius) {
rtrs_iu_free(con->rsp_ius, clt_path->s.dev->ib_dev,
@@ -1746,7 +1770,8 @@ static void destroy_con_cq_qp(struct rtrs_clt_con *con)
con->rsp_ius = NULL;
con->queue_num = 0;
}
+ rtrs_info(clt_path->clt, "%s: clt_path->s.dev_ref: %d, pd %px, ref: %d\n", __func__, clt_path->s.dev_ref, &pd->elem, rxe_read(pd));
if (clt_path->s.dev_ref && !--clt_path->s.dev_ref) {
rtrs_ib_dev_put(clt_path->s.dev);
clt_path->s.dev = NULL;
>
> Thanks,
> Guoqing