Messages in this thread | | | Date | Thu, 6 Jan 2022 21:02:34 +0800 | Subject | Re: [RFC PATCH net v2 1/2] net/smc: Resolve the race between link group access and termination | From | Wen Gu <> |
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Thanks for your reply.
On 2022/1/5 8:03 pm, Karsten Graul wrote: > On 05/01/2022 09:27, Wen Gu wrote: >> On 2022/1/3 6:36 pm, Karsten Graul wrote: >>> On 31/12/2021 10:44, Wen Gu wrote: >>>> On 2021/12/29 8:56 pm, Karsten Graul wrote: >>>>> On 28/12/2021 16:13, Wen Gu wrote: >>>>>> We encountered some crashes caused by the race between the access >>>>>> and the termination of link groups. >> So I think checking conn->alert_token_local has the same effect with checking conn->lgr to >> identify whether the link group pointed by conn->lgr is still healthy and able to be used. > > Yeah that sounds like a good solution for that! So is it now guaranteed that conn->lgr is always > set and this check can really be removed completely, or should there be a new helper that checks > conn->lgr and the alert_token, like smc_lgr_valid() ?
In my humble opinion, the link group pointed by conn->lgr might have the following three stages if we remove 'conn->lgr = NULL' from smc_lgr_unregister_conn().
1. conn->lgr = NULL and conn->alert_token_local is zero
This means that the connection has never been registered in a link group. conn->lgr is clearly unable to use.
2. conn->lgr != NULL and conn->alert_token_local is non-zero
This means that the connection has been registered in a link group, and conn->lgr is valid to access.
3. conn->lgr != NULL but conn->alert_token_local is zero
This means that the connection was registered in a link group before, but is unregistered from it now. conn->lgr shouldn't be used anymore.
So I am trying this way:
1) Introduce a new helper smc_conn_lgr_state() to check the three stages mentioned above.
enum smc_conn_lgr_state { SMC_CONN_LGR_ORPHAN, /* conn was never registered in a link group */ SMC_CONN_LGR_VALID, /* conn is registered in a link group now */ SMC_CONN_LGR_INVALID, /* conn was registered in a link group, but now is unregistered from it and conn->lgr should not be used any more */ };
2) replace the current conn->lgr check with the new helper.
These new changes are under testing now.
What do you think about it? :)
Thanks, Wen Gu
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