net: sched: remove one pair of atomic operations

__QDISC_STATE_RUNNING is only set/cleared from contexts owning qdisc lock.

Thus we can use less expensive bit operations, as we were doing
before commit f9eb8aea2a1e ("net_sched: transform qdisc running bit into a seqcount")

Fixes: 29cbcd858283 ("net: sched: Remove Qdisc::running sequence counter")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ahmed S. Darwish <a.darwish@linutronix.de>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Tested-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index e0988c5..ada02c4 100644 (file)
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -38,10 +38,13 @@ enum qdisc_state_t {
        __QDISC_STATE_DEACTIVATED,
        __QDISC_STATE_MISSED,
        __QDISC_STATE_DRAINING,
+};
+
+enum qdisc_state2_t {
        /* Only for !TCQ_F_NOLOCK qdisc. Never access it directly.
         * Use qdisc_run_begin/end() or qdisc_is_running() instead.
         */
-       __QDISC_STATE_RUNNING,
+       __QDISC_STATE2_RUNNING,
 };
 
 #define QDISC_STATE_MISSED     BIT(__QDISC_STATE_MISSED)
@@ -114,6 +117,7 @@ struct Qdisc {
        struct gnet_stats_basic_sync bstats;
        struct gnet_stats_queue qstats;
        unsigned long           state;
+       unsigned long           state2; /* must be written under qdisc spinlock */
        struct Qdisc            *next_sched;
        struct sk_buff_head     skb_bad_txq;
 
@@ -154,7 +158,7 @@ static inline bool qdisc_is_running(struct Qdisc *qdisc)
 {
        if (qdisc->flags & TCQ_F_NOLOCK)
                return spin_is_locked(&qdisc->seqlock);
-       return test_bit(__QDISC_STATE_RUNNING, &qdisc->state);
+       return test_bit(__QDISC_STATE2_RUNNING, &qdisc->state2);
 }
 
 static inline bool nolock_qdisc_is_empty(const struct Qdisc *qdisc)
@@ -217,7 +221,7 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc)
                 */
                return spin_trylock(&qdisc->seqlock);
        }
-       return !test_and_set_bit(__QDISC_STATE_RUNNING, &qdisc->state);
+       return !__test_and_set_bit(__QDISC_STATE2_RUNNING, &qdisc->state2);
 }
 
 static inline void qdisc_run_end(struct Qdisc *qdisc)
@@ -229,7 +233,7 @@ static inline void qdisc_run_end(struct Qdisc *qdisc)
                                      &qdisc->state)))
                        __netif_schedule(qdisc);
        } else {
-               clear_bit(__QDISC_STATE_RUNNING, &qdisc->state);
+               __clear_bit(__QDISC_STATE2_RUNNING, &qdisc->state2);
        }
 }