Re: [GIT] Networking

Eric Dumazet
2010-08-16T20:22:28Z

Le lundi 16 août 2010 à 12:36 -0700, David Miller a écrit :

> I'm hesistent to say that we should put this kind of patch in.
>
> It will shut up lockdep for this specific case, but it also means
> that if we do any other kinds of locking in this sequence we will
> not validate it.
>
> The valuable of this is open for debate I guess.
>
> But locking is hard so I would say that disabling lockdep to kill a
> warning it generates should be an absolute last resort.
>
> I also don't think making the locking mechanics conditional upon
> LOCKDEP is sane either, exactly because it means lockdep is testing
> something other than what actually gets used in practice. :-)

Hmm, maybe just disable BH, not for whole duration, but for each cpu.

Its a bit late here and I prefer to close this problem before whole
earth shout on me.

Thanks

[PATCH] netfilter: {ip,ip6,arp}_tables: avoid lockdep false positive

After commit 24b36f019 (netfilter: {ip,ip6,arp}_tables: dont block
bottom half more than necessary), lockdep can raise a warning
because we attempt to lock a spinlock with BH enabled, while
the same lock is usually locked by another cpu in a softirq context.

Disable again BH to avoid these lockdep warnings.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Diagnosed-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Patrick McHardy <kaber@trash.net>
CC: Peter Zijlstra <peterz@infradead.org>
---
net/ipv4/netfilter/arp_tables.c | 2 ++
net/ipv4/netfilter/ip_tables.c | 2 ++
net/ipv6/netfilter/ip6_tables.c | 2 ++
3 files changed, 6 insertions(+)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 6bccba3..51d6c31 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -735,6 +735,7 @@ static void get_counters(const struct xt_table_info *t,
if (cpu == curcpu)
continue;
i = 0;
+ local_bh_disable();
xt_info_wrlock(cpu);
xt_entry_foreach(iter, t->entries[cpu], t->size) {
ADD_COUNTER(counters[i], iter->counters.bcnt,
@@ -742,6 +743,7 @@ static void get_counters(const struct xt_table_info *t,
++i;
}
xt_info_wrunlock(cpu);
+ local_bh_enable();
}
put_cpu();
}
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index c439721..97b64b2 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -909,6 +909,7 @@ get_counters(const struct xt_table_info *t,
if (cpu == curcpu)
continue;
i = 0;
+ local_bh_disable();
xt_info_wrlock(cpu);
xt_entry_foreach(iter, t->entries[cpu], t->size) {
ADD_COUNTER(counters[i], iter->counters.bcnt,
@@ -916,6 +917,7 @@ get_counters(const struct xt_table_info *t,
++i; /* macro does multi eval of i */
}
xt_info_wrunlock(cpu);
+ local_bh_enable();
}
put_cpu();
}
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 5359ef4..29a7bca 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -922,6 +922,7 @@ get_counters(const struct xt_table_info *t,
if (cpu == curcpu)
continue;
i = 0;
+ local_bh_disable();
xt_info_wrlock(cpu);
xt_entry_foreach(iter, t->entries[cpu], t->size) {
ADD_COUNTER(counters[i], iter->counters.bcnt,
@@ -929,6 +930,7 @@ get_counters(const struct xt_table_info *t,
++i;
}
xt_info_wrunlock(cpu);
+ local_bh_enable();
}
put_cpu();
}