Le mardi 05 juillet 2011 à 10:25 -0700, Dan Magenheimer a écrit : > > From: Eric Dumazet [mailto:eric.dumazet@xxxxxxxxx] > > Sent: Tuesday, July 05, 2011 10:31 AM > > To: Dan Magenheimer > > Cc: netdev@xxxxxxxxxxxxxxx; Konrad Wilk; linux-mm > > Subject: Re: [RFC] non-preemptible kernel socket for RAMster > > > > Le mardi 05 juillet 2011 à 08:54 -0700, Dan Magenheimer a écrit : > > > In working on a kernel project called RAMster* (where RAM on a > > > remote system may be used for clean page cache pages and for swap > > > pages), I found I have need for a kernel socket to be used when > > > in non-preemptible state. I admit to being a networking idiot, > > > but I have been successfully using the following small patch. > > > I'm not sure whether I am lucky so far... perhaps more > > > sockets or larger/different loads will require a lot more > > > changes (or maybe even make my objective impossible). > > > So I thought I'd post it for comment. I'd appreciate > > > any thoughts or suggestions. > > > > > > Thanks, > > > Dan > > > > > > * http://events.linuxfoundation.org/events/linuxcon/magenheimer > > > > > > diff -Napur linux-2.6.37/net/core/sock.c linux-2.6.37-ramster/net/core/sock.c > > > --- linux-2.6.37/net/core/sock.c 2011-07-03 19:14:52.267853088 -0600 > > > +++ linux-2.6.37-ramster/net/core/sock.c 2011-07-03 19:10:04.340980799 -0600 > > > @@ -1587,6 +1587,14 @@ static void __lock_sock(struct sock *sk) > > > __acquires(&sk->sk_lock.slock) > > > { > > > DEFINE_WAIT(wait); > > > + if (!preemptible()) { > > > + while (sock_owned_by_user(sk)) { > > > + spin_unlock_bh(&sk->sk_lock.slock); > > > + cpu_relax(); > > > + spin_lock_bh(&sk->sk_lock.slock); > > > + } > > > + return; > > > + } > > > > Hmm, was this tested on UP machine ? > > Hi Eric -- > > Thanks for the reply! > > I hadn't tested UP in awhile so am testing now, and it seems to > work OK so far. However, I am just testing my socket, *not* testing > sockets in general. Are you implying that this patch will > break (kernel) sockets in general on a UP machine? If so, > could you be more specific as to why? (Again, I said > I am a networking idiot. ;-) I played a bit with adding > a new SOCK_ flag and triggering off of that, but this > version of the patch seemed much simpler. Say you have two processes and socket S One process locks socket S, and is preempted by another process. This second process is non preemptible and try to lock same socket. -> deadlock, since P1 never releases socket S -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>