[Devel] [RFC][PATCH][LLC] Use existing sock refcnt debugging

[Pavel Emelyanov]

Hi, Arnaldo.

I've grep-ed through the code and found one more place, where
the sk refcnt debugging is required, but is still performed in
an old fashion - this is the LLC2.

The problem in using the sk_refcnt_debug_xxx here is that these
socks do not provide the sk_destruct callback to catch the 
moment of the sock destruction.

Making this callback mandatory is not a good solution, as most 
often it will be empty and thus useless. Making this callback 
be set under the #ifdef SOCK_REFCNT_DEBUG is even more ugly 
than the previous one.

So, I propose to extend the sk_refcnt_debug_xxx set of helperf 
for those socks not having the sk_destruct callback by default,
like the LLC2 ones.

The new helper is sk_refcnt_debug_inc_undo(sk) sets the 
sk_destruct callback into the sk_refcnt_debug_dec() in case the
SOCK_REFCNT_DEBUG is on.

What do you think about it?

Signed-off-by: Pavel Emelyanov <xemul at openvz.org>

---

diff --git a/include/net/sock.h b/include/net/sock.h
index 5504fb9..1404ab9 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -654,10 +654,21 @@ static inline void sk_refcnt_debug_release(const struct sock *sk)
 		printk(KERN_DEBUG "Destruction of the %s socket %p delayed, refcnt=%d\n",
 		       sk->sk_prot->name, sk, atomic_read(&sk->sk_refcnt));
 }
+
+/*
+ * this one is to be used *only* for thouse socks, that
+ * do not have their own sk_destruct callback
+ */
+static inline void sk_refcnt_debug_inc_undo(struct sock *sk)
+{
+	sk_refcnt_debug_inc(sk);
+	sk->sk_destruct = sk_refcnt_debug_dec;
+}
 #else /* SOCK_REFCNT_DEBUG */
 #define sk_refcnt_debug_inc(sk) do { } while (0)
 #define sk_refcnt_debug_dec(sk) do { } while (0)
 #define sk_refcnt_debug_release(sk) do { } while (0)
+#define sk_refcnt_debug_inc_undo(sk) do { } while (0)
 #endif /* SOCK_REFCNT_DEBUG */
 
 /* Called with local bh disabled */
diff --git a/net/llc/llc_conn.c b/net/llc/llc_conn.c
index 5c0b484..6ee8778 100644
--- a/net/llc/llc_conn.c
+++ b/net/llc/llc_conn.c
@@ -775,11 +775,6 @@ drop_unlock:
 	goto out;
 }
 
-#undef LLC_REFCNT_DEBUG
-#ifdef LLC_REFCNT_DEBUG
-static atomic_t llc_sock_nr;
-#endif
-
 /**
  *	llc_backlog_rcv - Processes rx frames and expired timers.
  *	@sk: LLC sock (p8022 connection)
@@ -875,11 +870,7 @@ struct sock *llc_sk_alloc(struct net *net, int family, gfp_t priority, struct pr
 		goto out;
 	llc_sk_init(sk);
 	sock_init_data(NULL, sk);
-#ifdef LLC_REFCNT_DEBUG
-	atomic_inc(&llc_sock_nr);
-	printk(KERN_DEBUG "LLC socket %p created in %s, now we have %d alive\n", sk,
-		__FUNCTION__, atomic_read(&llc_sock_nr));
-#endif
+	sk_refcnt_debug_inc_undo(sk);
 out:
 	return sk;
 }
@@ -905,18 +896,7 @@ void llc_sk_free(struct sock *sk)
 	skb_queue_purge(&sk->sk_receive_queue);
 	skb_queue_purge(&sk->sk_write_queue);
 	skb_queue_purge(&llc->pdu_unack_q);
-#ifdef LLC_REFCNT_DEBUG
-	if (atomic_read(&sk->sk_refcnt) != 1) {
-		printk(KERN_DEBUG "Destruction of LLC sock %p delayed in %s, cnt=%d\n",
-			sk, __FUNCTION__, atomic_read(&sk->sk_refcnt));
-		printk(KERN_DEBUG "%d LLC sockets are still alive\n",
-			atomic_read(&llc_sock_nr));
-	} else {
-		atomic_dec(&llc_sock_nr);
-		printk(KERN_DEBUG "LLC socket %p released in %s, %d are still alive\n", sk,
-			__FUNCTION__, atomic_read(&llc_sock_nr));
-	}
-#endif
+	sk_refcnt_debug_release(sk);
 	sock_put(sk);
 }