gen_estimator: deadlock fix
One of my test machine got a deadlock during "tc" sessions,
adding/deleting classes & filters, using traffic estimators.
After some analysis, I believe we have a potential use after free case
in est_timer() :
spin_lock(e->stats_lock); << HERE >>
read_lock(&est_lock);
if (e->bstats == NULL) << TEST >>
goto skip;
Test is done a bit late, because after estimator is killed, and before
rcu grace period elapsed, we might already have freed/reuse memory where
e->stats_locks points to (some qdisc->q.lock)
A possible fix is to respect a rcu grace period at Qdisc dismantle time.
On 64bit, sizeof(struct Qdisc) is exactly 192 bytes. Adding 16 bytes to
it (for struct rcu_head) is a problem because it might change
performance, given QDISC_ALIGNTO is 32 bytes.
This is why I also change QDISC_ALIGNTO to 64 bytes, to satisfy most
current alignment requirements.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 67dc08e..03ca5d8 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -73,6 +73,7 @@
struct sk_buff_head q;
struct gnet_stats_basic_packed bstats;
struct gnet_stats_queue qstats;
+ struct rcu_head rcu_head;
};
struct Qdisc_class_ops {