From: Haggai Eran <haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
To: Jason Gunthorpe
<jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
Cc: Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
<linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
<netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Liran Liss <liranl-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
Guy Shapiro <guysh-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
Shachar Raindel <raindel-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>,
Yotam Kenneth <yotamke-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
Subject: Re: [PATCH v3 for-next 05/13] IB/cm: Reference count ib_cm_ids
Date: Wed, 13 May 2015 13:20:22 +0300 [thread overview]
Message-ID: <55532566.9040105@mellanox.com> (raw)
In-Reply-To: <20150512185447.GA3503-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
On 12/05/2015 21:54, Jason Gunthorpe wrote:
> On Tue, May 12, 2015 at 09:50:51AM +0300, Haggai Eran wrote:
>> Looking at the code though, I now notice that the other call site to
>> cm_destroy_id, from within the error path of cm_process_work could now
>> theoretically destroy an ID with existing references. Is that what you
>> meant?
>
> No, but that is certainly a problem.
>
>> Since only listening CM IDs are now shared in RDMA CM, this should not
>> happen in this patch-set, but perhaps the code can be changed to
>> make
>
> I think you need to enforce those semantics..
>
> Firstly, it looks to me like we, again, have two krefs, the one you
> added and the 'ref_count' in the priv structure which is 99% of a
> kref. So, again, don't do that.
>
> If you want to share listening CM IDs, then do exactly and only
> that. Use the existing ref count scheme for keeping track of the
> kfree/etc,
The existing reference count scheme is for synchronization in
cm_destroy_id. The function waits for active handlers to complete before
destroying the id. Decrementing ref_count to zero doesn't cause the id
to be freed.
> and add some kind of sharable listen ref count.
That's basically what the patch does. I can change it from a kref to a
direct reference count if you prefer.
> Early exit
> from cm_destroy_id when the there are still people listening.
>
> That sounds like it keeps the basic rule of cm_destroy_id being
> properly paired with the alloc, and allows listen sharing without the
> confusion of what does multiple destroy mean.
Won't you find it confusing if a call to ib_destroy_cm_id is successful
but the id actually continues to live? I prefer the API to explicitly
show that you are only decreasing the reference count and that the id
might not be destroyed immediately.
Regards,
Haggai
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next prev parent reply other threads:[~2015-05-13 10:20 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-10 10:26 [PATCH v3 for-next 00/13] Add network namespace support in the RDMA-CM Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 01/13] IB/core: Use SRCU when reading client_list or device_list Haggai Eran
2015-05-11 18:18 ` Jason Gunthorpe
2015-05-12 6:07 ` Haggai Eran
2015-05-12 18:23 ` Jason Gunthorpe
2015-05-13 8:10 ` Haggai Eran
[not found] ` <555306E7.9020000-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2015-05-13 15:57 ` Jason Gunthorpe
2015-05-14 10:35 ` Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 02/13] IB/addr: Pass network namespace as a parameter Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 05/13] IB/cm: Reference count ib_cm_ids Haggai Eran
[not found] ` <1431253604-9214-6-git-send-email-haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2015-05-11 18:34 ` Jason Gunthorpe
2015-05-12 6:50 ` Haggai Eran
[not found] ` <5551A2CB.1010407-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2015-05-12 18:54 ` Jason Gunthorpe
[not found] ` <20150512185447.GA3503-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-05-13 10:20 ` Haggai Eran [this message]
2015-05-13 16:58 ` Jason Gunthorpe
[not found] ` <20150513165823.GA20343-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-05-14 6:48 ` Haggai Eran
2015-05-15 19:11 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A8FDC0C3-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-05-17 6:27 ` Haggai Eran
2015-05-19 19:23 ` Jason Gunthorpe
[not found] ` <20150519192353.GA23612-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-05-19 22:52 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A8FDD412-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-05-19 23:46 ` Jason Gunthorpe
[not found] ` <20150519234654.GA26634-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-05-20 0:49 ` Hefty, Sean
2015-05-21 6:51 ` Haggai Eran
[not found] ` <555D806B.1090002-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2015-05-21 12:56 ` Hefty, Sean
[not found] ` <1431253604-9214-1-git-send-email-haggaie-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2015-05-10 10:26 ` [PATCH v3 for-next 03/13] IB/core: Find the network namespace matching connection parameters Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 04/13] IB/ipoib: Return IPoIB devices " Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 06/13] IB/cm: API to retrieve existing listening CM IDs Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 07/13] IB/cm: Expose service ID in request events Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 08/13] IB/cma: Refactor RDMA IP CM private-data parsing code Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 09/13] IB/cma: Add compare_data checks to the RDMA CM module Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 10/13] IB/cma: Separate port allocation to network namespaces Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 11/13] IB/cma: Share CM IDs between namespaces Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 12/13] IB/cma: Add support for network namespaces Haggai Eran
2015-05-10 10:26 ` [PATCH v3 for-next 13/13] IB/ucma: Take the network namespace from the process Haggai Eran
2015-05-12 17:52 ` [PATCH v3 for-next 00/13] Add network namespace support in the RDMA-CM Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A8FD7B85-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-05-13 8:50 ` Haggai Eran
[not found] ` <55531073.1000305-VPRAkNaXOzVWk0Htik3J/w@public.gmane.org>
2015-05-13 16:45 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A8FDA13B-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-05-13 17:18 ` Jason Gunthorpe
[not found] ` <20150513171823.GB20343-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2015-05-13 17:30 ` Hefty, Sean
[not found] ` <1828884A29C6694DAF28B7E6B8A82373A8FDA1AB-P5GAC/sN6hkd3b2yrw5b5LfspsVTdybXVpNB7YpNyf8@public.gmane.org>
2015-05-14 5:35 ` Haggai Eran
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