From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Santosh Shilimkar <santosh.shilimkar@oracle.com>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
rds-devel@oss.oracle.com
Subject: Re: [Patch net] rds: mark bound socket with SOCK_RCU_FREE
Date: Mon, 10 Sep 2018 20:24:23 -0400 [thread overview]
Message-ID: <20180911002423.GL4668@oracle.com> (raw)
In-Reply-To: <CAM_iQpXcydKdTyT25F5Bbk7y9BMJLTKMT42o3J0bbuodjXjetA@mail.gmail.com>
On (09/10/18 17:16), Cong Wang wrote:
> >
> > On (09/10/18 16:51), Cong Wang wrote:
> > >
> > > __rds_create_bind_key(key, addr, port, scope_id);
> > > - rs = rhashtable_lookup_fast(&bind_hash_table, key, ht_parms);
> > > + rcu_read_lock();
> > > + rs = rhashtable_lookup(&bind_hash_table, key, ht_parms);
> > > if (rs && !sock_flag(rds_rs_to_sk(rs), SOCK_DEAD))
> > > rds_sock_addref(rs);
> > > else
> > > rs = NULL;
> > > + rcu_read_unlock();
> >
> > aiui, the rcu_read lock/unlock is only useful if the write
> > side doing destructive operations does something to make sure readers
> > are done before doing the destructive opertion. AFAIK, that does
> > not exist for rds socket management today
>
> That is exactly why we need it here, right?
Maybe I am confused, what exactly is the patch you are proposing?
Does it have the SOCK_RCU_FREE change?
Does it have the rcu_read_lock you have above?
Where is the call_rcu?
> Hmm, so you are saying synchronize_rcu() is kinda more correct
> than call_rcu()??
I'm not saying that, I'm asking "what exactly is the patch
you are proposing?" The only one on record is
http://patchwork.ozlabs.org/patch/968282/
which does not have either synchronize_rcu or call_rcu.
> I never hear this before, would like to know why.
Please post precise patches first.
Thanks.
next prev parent reply other threads:[~2018-09-11 5:21 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-10 22:24 [Patch net] rds: mark bound socket with SOCK_RCU_FREE Cong Wang
2018-09-10 22:34 ` Sowmini Varadhan
2018-09-10 22:43 ` Santosh Shilimkar
2018-09-10 23:30 ` Sowmini Varadhan
2018-09-10 23:51 ` Cong Wang
2018-09-11 0:04 ` Sowmini Varadhan
2018-09-11 0:16 ` Cong Wang
2018-09-11 0:24 ` Sowmini Varadhan [this message]
2018-09-11 0:39 ` Cong Wang
2018-09-11 0:26 ` Santosh Shilimkar
2018-09-11 0:45 ` Cong Wang
2018-09-11 0:56 ` Santosh Shilimkar
2018-09-11 0:59 ` Cong Wang
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