net_sched: fix THROTTLED/RUNNING race
commit fd245a4adb52 (net_sched: move TCQ_F_THROTTLED flag)
added a race.
qdisc_watchdog() is run from softirq, so special care should be taken or
we can lose one state transition (THROTTLED/RUNNING)
Prior to fd245a4adb52, we were manipulating q->flags (qdisc->flags &=
~TCQ_F_THROTTLED;) and this manipulation could only race with
qdisc_warn_nonwc().
Since we want to avoid atomic ops in qdisc fast path - it was the
meaning of commit 371121057607e (QDISC_STATE_RUNNING dont need atomic
bit ops) - fix is to move THROTTLE bit into 'state' field, this one
being manipulated with SMP and IRQ safe operations.
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 a9505b6..b931f02 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -25,6 +25,7 @@
enum qdisc_state_t {
__QDISC_STATE_SCHED,
__QDISC_STATE_DEACTIVATED,
+ __QDISC_STATE_THROTTLED,
};
/*
@@ -32,7 +33,6 @@
*/
enum qdisc___state_t {
__QDISC___STATE_RUNNING = 1,
- __QDISC___STATE_THROTTLED = 2,
};
struct qdisc_size_table {
@@ -106,17 +106,17 @@
static inline bool qdisc_is_throttled(const struct Qdisc *qdisc)
{
- return (qdisc->__state & __QDISC___STATE_THROTTLED) ? true : false;
+ return test_bit(__QDISC_STATE_THROTTLED, &qdisc->state) ? true : false;
}
static inline void qdisc_throttled(struct Qdisc *qdisc)
{
- qdisc->__state |= __QDISC___STATE_THROTTLED;
+ set_bit(__QDISC_STATE_THROTTLED, &qdisc->state);
}
static inline void qdisc_unthrottled(struct Qdisc *qdisc)
{
- qdisc->__state &= ~__QDISC___STATE_THROTTLED;
+ clear_bit(__QDISC_STATE_THROTTLED, &qdisc->state);
}
struct Qdisc_class_ops {