pkt_sched: Use qdisc_lock() on already sampled root qdisc.
Based upon a bug report by Jeff Kirsher.
Don't use qdisc_root_lock() in these cases as the root
qdisc could have been changed, and we'd thus lock the
wrong object.
Tested by Emil S Tantilov who confirms that this seems
to fix the problem.
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/dev.c b/net/core/dev.c
index 69320a5..da7acac 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1796,7 +1796,7 @@
skb->tc_verd = SET_TC_AT(skb->tc_verd,AT_EGRESS);
#endif
if (q->enqueue) {
- spinlock_t *root_lock = qdisc_root_lock(q);
+ spinlock_t *root_lock = qdisc_lock(q);
spin_lock(root_lock);
@@ -1995,7 +1995,7 @@
smp_mb__before_clear_bit();
clear_bit(__QDISC_STATE_SCHED, &q->state);
- root_lock = qdisc_root_lock(q);
+ root_lock = qdisc_lock(q);
if (spin_trylock(root_lock)) {
qdisc_run(q);
spin_unlock(root_lock);
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 9c9cd4d..7cf83b3 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -29,7 +29,7 @@
/* Main transmission queue. */
/* Modifications to data participating in scheduling must be protected with
- * qdisc_root_lock(qdisc) spinlock.
+ * qdisc_lock(qdisc) spinlock.
*
* The idea is the following:
* - enqueue, dequeue are serialized via qdisc root lock
@@ -126,7 +126,7 @@
if (unlikely((skb = dequeue_skb(q)) == NULL))
return 0;
- root_lock = qdisc_root_lock(q);
+ root_lock = qdisc_lock(q);
/* And release qdisc */
spin_unlock(root_lock);
@@ -507,7 +507,7 @@
}
EXPORT_SYMBOL(qdisc_create_dflt);
-/* Under qdisc_root_lock(qdisc) and BH! */
+/* Under qdisc_lock(qdisc) and BH! */
void qdisc_reset(struct Qdisc *qdisc)
{
@@ -543,7 +543,7 @@
kfree((char *) qdisc - qdisc->padded);
}
-/* Under qdisc_root_lock(qdisc) and BH! */
+/* Under qdisc_lock(qdisc) and BH! */
void qdisc_destroy(struct Qdisc *qdisc)
{
@@ -659,7 +659,7 @@
dev_queue = netdev_get_tx_queue(dev, i);
q = dev_queue->qdisc;
- root_lock = qdisc_root_lock(q);
+ root_lock = qdisc_lock(q);
if (lock)
spin_lock_bh(root_lock);
@@ -735,7 +735,7 @@
struct Qdisc *qdisc_default = _qdisc_default;
if (qdisc) {
- spinlock_t *root_lock = qdisc_root_lock(qdisc);
+ spinlock_t *root_lock = qdisc_lock(qdisc);
dev_queue->qdisc = qdisc_default;
dev_queue->qdisc_sleeping = qdisc_default;