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Message-ID: <20070912152058.GB9830@linux.vnet.ibm.com> Date: Wed, 12 Sep 2007 08:20:58 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Vlad Yasevich <vladislav.yasevich@...com> Cc: Sridhar Samudrala <sri@...ibm.com>, netdev@...r.kernel.org, lksctp-developers@...ts.sourceforge.net Subject: Re: [RFC PATCH 1/2] SCTP: Add RCU synchronization around sctp_localaddr_list On Tue, Sep 11, 2007 at 10:05:10AM -0400, Vlad Yasevich wrote: > Sridhar, Paul > > Thanks for review. Some answers and questions below... NP! > Sridhar Samudrala wrote: > > Paul E. McKenney wrote: [ . . . ] > >>> if ((PF_INET == sk->sk_family) && > >>> (AF_INET6 == addr->a.sa.sa_family)) > >>> continue; > >>> + > >>> cnt++; > >>> } > >>> + rcu_read_unlock(); > >> > >> We are just counting these things, right? If on the other hand we are > >> keeping a reference outside of rcu_read_lock() protection, then there > >> needs to be some explicit mechanism preventing the corresponding entry > >> from being freed. > > In this particular case, we are just counting. There are other cases, > we make a copy of the address in the list. The goal was to reduce the > probability that an address that is about to be deleted at the rcu > quiescent state will not be copied/counted. > > My other thought was to use atomics, but with all the yelling about atomic_read(), > that didn't seem any better then a simple __u8 flag. If just counting, then no worries either way. As long as you are counting to a local variable, as in fact you are. Thanx, Paul - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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