From: Eric Dumazet Date: Thu, 24 Mar 2011 07:13:14 +0000 (-0700) Subject: net_sched: fix THROTTLED/RUNNING race X-Git-Tag: v2.6.39-rc1~54^2~7 X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=ef352e7cdf714596f51ad18809404edeaa50e8fd;p=~emulex%2Finfiniband.git 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 --- diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index a9505b6a18e..b931f021d7a 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 {