| Message ID | 20150517024534.GA5570@gondor.apana.org.au |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Herbert Xu <herbert@gondor.apana.org.au> Date: Sun, 17 May 2015 10:45:34 +0800 > On Sat, May 16, 2015 at 05:08:19PM -0400, David Miller wrote: >> >> As far as I can tell, this ought to be fine as-is. > > OK what about dropping the global rover altogether? Let's just > start randomly like UDP. > > ---8<--- > Currently we use a global rover to select a port ID that is unique. > This used to work consistently when it was protected with a global > lock. However as we're now lockless, the global rover can exhibit > pathological behaviour should multiple threads all stomp on it at > the same time. > > Granted this will eventually resolve itself but the process is > suboptimal. > > This patch replaces the global rover with a pseudorandom starting > point to avoid this issue. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Yep, this is fine, applied. Thanks! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index ec4adbd..716c6d2 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1296,20 +1296,24 @@ static int netlink_autobind(struct socket *sock) struct netlink_table *table = &nl_table[sk->sk_protocol]; s32 portid = task_tgid_vnr(current); int err; - static s32 rover = -4097; + s32 rover = -4096; + bool ok; retry: cond_resched(); rcu_read_lock(); - if (__netlink_lookup(table, portid, net)) { + ok = !__netlink_lookup(table, portid, net); + rcu_read_unlock(); + if (!ok) { /* Bind collision, search negative portid values. */ - portid = rover--; - if (rover > -4097) + if (rover == -4096) + /* rover will be in range [S32_MIN, -4097] */ + rover = S32_MIN + prandom_u32_max(-4096 - S32_MIN); + else if (rover >= -4096) rover = -4097; - rcu_read_unlock(); + portid = rover--; goto retry; } - rcu_read_unlock(); err = netlink_insert(sk, portid); if (err == -EADDRINUSE)