path: root/include/net/pkt_sched.h
diff options
authorEric Dumazet <eric.dumazet@gmail.com>2010-03-31 07:06:04 +0000
committerDavid S. Miller <davem@davemloft.net>2010-04-01 18:38:48 -0700
commit5d944c640b4ae5f37c537acf491c2f0eb89fa0d6 (patch)
tree9195a0135ec21c1c06ff4d46e8cf7924e2c364c0 /include/net/pkt_sched.h
parentd4fc6dbb5ae51430e35b2005f6d68938861f8d8b (diff)
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>
Diffstat (limited to 'include/net/pkt_sched.h')
1 files changed, 1 insertions, 1 deletions
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index b6cdc33b39c..9d4d87cc970 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -12,7 +12,7 @@ struct qdisc_walker {
int (*fn)(struct Qdisc *, unsigned long cl, struct qdisc_walker *);
-#define QDISC_ALIGNTO 32
+#define QDISC_ALIGNTO 64
#define QDISC_ALIGN(len) (((len) + QDISC_ALIGNTO-1) & ~(QDISC_ALIGNTO-1))
static inline void *qdisc_priv(struct Qdisc *q)