From: Karsten Graul <kgraul@linux.ibm.com>
To: Wen Gu <guwen@linux.alibaba.com>, davem@davemloft.net, kuba@kernel.org
Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, dust.li@linux.alibaba.com,
tonylu@linux.alibaba.com
Subject: Re: [RFC PATCH net v2 1/2] net/smc: Resolve the race between link group access and termination
Date: Wed, 29 Dec 2021 13:56:42 +0100 [thread overview]
Message-ID: <4ec6e460-96d1-fedc-96ff-79a98fd38de8@linux.ibm.com> (raw)
In-Reply-To: <1640704432-76825-2-git-send-email-guwen@linux.alibaba.com>
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.
While I agree with the problems you found I am not sure if the solution is the right one.
At the moment conn->lgr is checked all over the code as indication if a connection
still has a valid link group. When you change this semantic by leaving conn->lgr set
after the connection was unregistered from its link group then I expect various new problems
to happen.
For me the right solution would be to use correct locking before conn->lgr is checked and used.
In smc_lgr_unregister_conn() the lgr->conns_lock is used when conn->lgr is unset (note that
it is better to have that "conn->lgr = NULL;" line INSIDE the lock in this function).
And on any places in the code where conn->lgr is used you get the read_lock while lgr is accessed.
This could solve the problem, using existing mechanisms, right? Opinions?
next prev parent reply other threads:[~2021-12-29 12:56 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-28 15:13 [RFC PATCH net v2 0/2] net/smc: Fix for race in smc link group termination Wen Gu
2021-12-28 15:13 ` [RFC PATCH net v2 1/2] net/smc: Resolve the race between link group access and termination Wen Gu
2021-12-29 12:56 ` Karsten Graul [this message]
2021-12-31 9:44 ` Wen Gu
2022-01-03 10:36 ` Karsten Graul
2022-01-05 8:27 ` Wen Gu
2022-01-05 12:03 ` Karsten Graul
2022-01-06 13:02 ` Wen Gu
2022-01-07 9:54 ` Karsten Graul
2022-01-07 12:04 ` Wen Gu
2021-12-28 15:13 ` [RFC PATCH net v2 2/2] net/smc: Resolve the race between SMC-R link access and clear Wen Gu
2021-12-29 12:51 ` Karsten Graul
2021-12-30 4:00 ` dust.li
2021-12-31 9:45 ` Wen Gu
2022-01-03 10:39 ` Karsten Graul
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