Messages in this thread | | | Date | Fri, 14 Apr 2023 11:40:35 +0800 | From | Guoqing Jiang <> | Subject | Re: [PATCH for-next 2/3] RDMA/rtrs: Fix rxe_dealloc_pd warning |
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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?
>> Then what is the appropriate time to call destroy_con_cq_qp for this scenario? >> Otherwise there could be memory leak. > we must ensure QP in con[0] is closed before destroying the PD. > Currently destroy_con_cq_qp() subroutine will close the opened QP first.
Let me try another way, with below change, rtrs_ib_dev_put can't be called from destroy_con_cq_qp, right?
+ if (!con->has_dev) + return; if (clt_path->s.dev_ref && !--clt_path->s.dev_ref) { rtrs_ib_dev_put(clt_path->s.dev); clt_path->s.dev = NULL;
Then when will you dealloc pd and free rtrs_ib_dev?
Thanks, Guoqing
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