Messages in this thread | | | Date | Thu, 25 Sep 2008 08:29:36 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 1/1] Use RCU for the UDP hash lock |
| |
On Wed, Sep 24, 2008 at 03:46:20PM -0500, Corey Minyard wrote: > Stephen Hemminger wrote: >> >>> static inline void udp_lib_unhash(struct sock *sk) >>> { >>> - write_lock_bh(&udp_hash_lock); >>> - if (sk_del_node_init(sk)) { >>> + spin_lock_bh(&udp_hash_wlock); >>> + if (sk_del_node_rcu(sk)) { >>> inet_sk(sk)->num = 0; >>> sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1); >>> } >>> - write_unlock_bh(&udp_hash_lock); >>> + spin_unlock_bh(&udp_hash_wlock); >>> + synchronize_sched(); >>> >> >> Could this be synchronize_rcu? You are using rcu_read_lock() protected >> sections. >> > I meant to comment on that. I wasn't sure which to use, so I chose the > more conservative approach. synchronize_rcu() might be appropriate.
You do indeed need to match the update-side and read-side primitives:
Update-side Read-side
synchronize_rcu() rcu_read_lock() call_rcu() rcu_read_unlock()
call_rcu_bh() rcu_read_lock_bh() rcu_read_unlock_bh()
synchronize_sched() preempt_disable() preempt_enable() [and anything else that disables either preemption or irqs]
synchronize_srcu() srcu_read_lock() srcu_read_unlock()
Mixing RCU or RCU-SCHED with RCU-BH will fail in Classic RCU systems, while mixing RCU or RCU-BH with RCU-SCHED will fail in preemptable RCU systems. Mixing SRCU with any of the other flavors of RCU will fail on any system.
So please match them up correctly!
Thanx, Paul
| |