I could see spin lock (&sk->sk_receive_queue.lock) is acquired before queing sk_buff . This is done in interrupt context ( called from bottom half, http://lxr.linux.no/#linux+v3.13.5/net/packet/af_packet.c#L1818 ). userspace can receive the packet using system call and system call will acquire the same lock ( http://lxr.linux.no/#linux+v3.13.5/net/core/datagram.c#L191 ). Suppose in smp machine, if bottom half is executed by cpu #1 and the userspace process is pinned to cpu #2. How can the spin lock acuquired info ( lock value ) will be reflected to cpu #2 ( if cpu #2 has already acquired and released the lock value and the lock value is stored in a cpu #2 data cache. so if cpu #1 acquire it , cpu#2 will read the cache value which says it is free). I could see that spin_lock_t is not a volatile value also. Thanks, Ratheesh -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
