From ef352e7cdf714596f51ad18809404edeaa50e8fd Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 24 Mar 2011 00:13:14 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/net/sch_generic.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index a9505b6a18e3..b931f021d7ab 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -25,6 +25,7 @@ struct qdisc_rate_table { enum qdisc_state_t { __QDISC_STATE_SCHED, __QDISC_STATE_DEACTIVATED, + __QDISC_STATE_THROTTLED, }; /* @@ -32,7 +33,6 @@ enum qdisc_state_t { */ enum qdisc___state_t { __QDISC___STATE_RUNNING = 1, - __QDISC___STATE_THROTTLED = 2, }; struct qdisc_size_table { @@ -106,17 +106,17 @@ static inline void qdisc_run_end(struct Qdisc *qdisc) 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 {