Re: [PATCH][PPPOL2TP]: Fix SMP oops in pppol2tp driver

James Chapman
2008-02-25T12:20:10Z

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Jarek Poplawski wrote:
> Jarek Poplawski wrote, On 02/21/2008 01:08 PM:
> ...
>
>> Another, probably simpler way would be to move almost all pppol2tp_xmit
> ...
>
> Actually, the simplest off all seems to be now this old idea to maybe make
> sk_dst_lock globally softirq immune. At least I think it's worth of testing,
> to check for these other possible lockdep warnings. It should only need to
> change all write_ and read_lock(&sk->sk_dst_lock) in very few places:
> include/net/sock.h, include/net/ip6_route.h, and net/ipv6/ipv6_sockglue.c.
> This could be tested together with you full _bh locking patch (maybe except
> these other changes in pppol2tp_xmit).

I did this and all lockdep errors have now gone. Tests ran all weekend.
See attached patch.

Is this an acceptable solution? If so, I'll prepare and send official
patches.

--
James Chapman
Katalix Systems Ltd
http://www.katalix.com
Catalysts for your Embedded Linux software development

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Index: linux-2.6.24.2/include/net/ip6_route.h
===================================================================
--- linux-2.6.24.2.orig/include/net/ip6_route.h
+++ linux-2.6.24.2/include/net/ip6_route.h
@@ -150,9 +150,9 @@ static inline void __ip6_dst_store(struc
static inline void ip6_dst_store(struct sock *sk, struct dst_entry *dst,
struct in6_addr *daddr, struct in6_addr *saddr)
{
- write_lock(&sk->sk_dst_lock);
+ write_lock_bh(&sk->sk_dst_lock);
__ip6_dst_store(sk, dst, daddr, saddr);
- write_unlock(&sk->sk_dst_lock);
+ write_unlock_bh(&sk->sk_dst_lock);
}

static inline int ipv6_unicast_destination(struct sk_buff *skb)
Index: linux-2.6.24.2/include/net/sock.h
===================================================================
--- linux-2.6.24.2.orig/include/net/sock.h
+++ linux-2.6.24.2/include/net/sock.h
@@ -1058,11 +1058,11 @@ sk_dst_get(struct sock *sk)
{
struct dst_entry *dst;

- read_lock(&sk->sk_dst_lock);
+ read_lock_bh(&sk->sk_dst_lock);
dst = sk->sk_dst_cache;
if (dst)
dst_hold(dst);
- read_unlock(&sk->sk_dst_lock);
+ read_unlock_bh(&sk->sk_dst_lock);
return dst;
}

@@ -1079,9 +1079,9 @@ __sk_dst_set(struct sock *sk, struct dst
static inline void
sk_dst_set(struct sock *sk, struct dst_entry *dst)
{
- write_lock(&sk->sk_dst_lock);
+ write_lock_bh(&sk->sk_dst_lock);
__sk_dst_set(sk, dst);
- write_unlock(&sk->sk_dst_lock);
+ write_unlock_bh(&sk->sk_dst_lock);
}

static inline void
@@ -1097,9 +1097,9 @@ __sk_dst_reset(struct sock *sk)
static inline void
sk_dst_reset(struct sock *sk)
{
- write_lock(&sk->sk_dst_lock);
+ write_lock_bh(&sk->sk_dst_lock);
__sk_dst_reset(sk);
- write_unlock(&sk->sk_dst_lock);
+ write_unlock_bh(&sk->sk_dst_lock);
}

extern struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie);
Index: linux-2.6.24.2/net/ipv6/ipv6_sockglue.c
===================================================================
--- linux-2.6.24.2.orig/net/ipv6/ipv6_sockglue.c
+++ linux-2.6.24.2/net/ipv6/ipv6_sockglue.c
@@ -440,9 +440,9 @@ static int do_ipv6_setsockopt(struct soc
opt = xchg(&np->opt, opt);
sk_dst_reset(sk);
} else {
- write_lock(&sk->sk_dst_lock);
+ write_lock_bh(&sk->sk_dst_lock);
opt = xchg(&np->opt, opt);
- write_unlock(&sk->sk_dst_lock);
+ write_unlock_bh(&sk->sk_dst_lock);
sk_dst_reset(sk);
}
sticky_done:
@@ -504,9 +504,9 @@ update:
opt = xchg(&np->opt, opt);
sk_dst_reset(sk);
} else {
- write_lock(&sk->sk_dst_lock);
+ write_lock_bh(&sk->sk_dst_lock);
opt = xchg(&np->opt, opt);
- write_unlock(&sk->sk_dst_lock);
+ write_unlock_bh(&sk->sk_dst_lock);
sk_dst_reset(sk);
}