Update Linux to v5.10.157
Sourced from [1]
[1] https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.157.tar.xz
Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: I7b30d9e98d8c465d6b44de8e7433b4a40b3289ba
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 1042c44..e7e8c31 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -163,37 +163,17 @@
if (spin_trylock(&qdisc->seqlock))
goto nolock_empty;
- /* Paired with smp_mb__after_atomic() to make sure
- * STATE_MISSED checking is synchronized with clearing
- * in pfifo_fast_dequeue().
+ /* No need to insist if the MISSED flag was already set.
+ * Note that test_and_set_bit() also gives us memory ordering
+ * guarantees wrt potential earlier enqueue() and below
+ * spin_trylock(), both of which are necessary to prevent races
*/
- smp_mb__before_atomic();
-
- /* If the MISSED flag is set, it means other thread has
- * set the MISSED flag before second spin_trylock(), so
- * we can return false here to avoid multi cpus doing
- * the set_bit() and second spin_trylock() concurrently.
- */
- if (test_bit(__QDISC_STATE_MISSED, &qdisc->state))
+ if (test_and_set_bit(__QDISC_STATE_MISSED, &qdisc->state))
return false;
- /* Set the MISSED flag before the second spin_trylock(),
- * if the second spin_trylock() return false, it means
- * other cpu holding the lock will do dequeuing for us
- * or it will see the MISSED flag set after releasing
- * lock and reschedule the net_tx_action() to do the
- * dequeuing.
- */
- set_bit(__QDISC_STATE_MISSED, &qdisc->state);
-
- /* spin_trylock() only has load-acquire semantic, so use
- * smp_mb__after_atomic() to ensure STATE_MISSED is set
- * before doing the second spin_trylock().
- */
- smp_mb__after_atomic();
-
- /* Retry again in case other CPU may not see the new flag
- * after it releases the lock at the end of qdisc_run_end().
+ /* Try to take the lock again to make sure that we will either
+ * grab it or the CPU that still has it will see MISSED set
+ * when testing it in qdisc_run_end()
*/
if (!spin_trylock(&qdisc->seqlock))
return false;
@@ -217,6 +197,12 @@
if (qdisc->flags & TCQ_F_NOLOCK) {
spin_unlock(&qdisc->seqlock);
+ /* spin_unlock() only has store-release semantic. The unlock
+ * and test_bit() ordering is a store-load ordering, so a full
+ * memory barrier is needed here.
+ */
+ smp_mb();
+
if (unlikely(test_bit(__QDISC_STATE_MISSED,
&qdisc->state))) {
clear_bit(__QDISC_STATE_MISSED, &qdisc->state);
@@ -1192,7 +1178,6 @@
static inline void qdisc_reset_queue(struct Qdisc *sch)
{
__qdisc_reset_queue(&sch->q);
- sch->qstats.backlog = 0;
}
static inline struct Qdisc *qdisc_replace(struct Qdisc *sch, struct Qdisc *new,