[PATCH net-next v2 0/5] Taprio qdisc fixes

[PATCH net-next v2 0/5] Taprio qdisc fixes

[Andre Guedes]

Hi all,

I'm re-sending this series, now with the "net-next" prefix in the subject.

The only change from the previous version is in patch 3. As suggested by Cong
Wang, it removes the !entry check within should_restart_cycle() since it is
already checked by the caller. As a side effect, that function becomes a dummy
wrapper on list_is_last() so we simply remove it and call list_is_last()
instead.

Best regards,

Andre

Andre Guedes (5):
  net: sched: taprio: Remove pointless variable assigment
  net: sched: taprio: Refactor taprio_get_start_time()
  net: sched: taprio: Remove should_restart_cycle()
  net: sched: taprio: Fix taprio_peek()
  net: sched: taprio: Fix taprio_dequeue()

 net/sched/sch_taprio.c | 56 +++++++++++++++++++++---------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

-- 
2.21.0

[PATCH net-next v2 1/5] net: sched: taprio: Remove pointless variable assigment

[Andre Guedes]

This patch removes a pointless variable assigment in taprio_change().
The 'err' variable is not used from this assignment to the next one so
this patch removes it.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
---
 net/sched/sch_taprio.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 001182aa3959..d91a7ec67348 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -651,7 +651,6 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 	if (err < 0)
 		return err;
 
-	err = -EINVAL;
 	if (tb[TCA_TAPRIO_ATTR_PRIOMAP])
 		mqprio = nla_data(tb[TCA_TAPRIO_ATTR_PRIOMAP]);
 
-- 
2.21.0

[PATCH net-next v2 2/5] net: sched: taprio: Refactor taprio_get_start_time()

[Andre Guedes]

This patch does a code refactoring to taprio_get_start_time() function
to improve readability and report error properly.

If 'base' time is later than 'now', the start time is equal to 'base'
and taprio_get_start_time() is done. That's the natural case so we move
that code to the beginning of the function. Also, if 'cycle' calculation
is zero, something went really wrong with taprio and we should log that
internal error properly.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
---
 net/sched/sch_taprio.c | 37 +++++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index d91a7ec67348..d0aae7b5e608 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -539,7 +539,7 @@ static int taprio_parse_mqprio_opt(struct net_device *dev,
 	return 0;
 }
 
-static ktime_t taprio_get_start_time(struct Qdisc *sch)
+static int taprio_get_start_time(struct Qdisc *sch, ktime_t *start)
 {
 	struct taprio_sched *q = qdisc_priv(sch);
 	struct sched_entry *entry;
@@ -547,27 +547,33 @@ static ktime_t taprio_get_start_time(struct Qdisc *sch)
 	s64 n;
 
 	base = ns_to_ktime(q->base_time);
-	cycle = 0;
+	now = q->get_time();
+
+	if (ktime_after(base, now)) {
+		*start = base;
+		return 0;
+	}
 
 	/* Calculate the cycle_time, by summing all the intervals.
 	 */
+	cycle = 0;
 	list_for_each_entry(entry, &q->entries, list)
 		cycle = ktime_add_ns(cycle, entry->interval);
 
-	if (!cycle)
-		return base;
-
-	now = q->get_time();
-
-	if (ktime_after(base, now))
-		return base;
+	/* The qdisc is expected to have at least one sched_entry.  Moreover,
+	 * any entry must have 'interval' > 0. Thus if the cycle time is zero,
+	 * something went really wrong. In that case, we should warn about this
+	 * inconsistent state and return error.
+	 */
+	if (WARN_ON(!cycle))
+		return -EFAULT;
 
 	/* Schedule the start time for the beginning of the next
 	 * cycle.
 	 */
 	n = div64_s64(ktime_sub_ns(now, base), cycle);
-
-	return ktime_add_ns(base, (n + 1) * cycle);
+	*start = ktime_add_ns(base, (n + 1) * cycle);
+	return 0;
 }
 
 static void taprio_start_sched(struct Qdisc *sch, ktime_t start)
@@ -716,9 +722,12 @@ static int taprio_change(struct Qdisc *sch, struct nlattr *opt,
 	}
 
 	taprio_set_picos_per_byte(dev, q);
-	start = taprio_get_start_time(sch);
-	if (!start)
-		return 0;
+
+	err = taprio_get_start_time(sch, &start);
+	if (err < 0) {
+		NL_SET_ERR_MSG(extack, "Internal error: failed get start time");
+		return err;
+	}
 
 	taprio_start_sched(sch, start);
 
-- 
2.21.0

[PATCH net-next v2 3/5] net: sched: taprio: Remove should_restart_cycle()

[Andre Guedes]

The 'entry' argument from should_restart_cycle() cannot be NULL since it
is already checked by the caller so the WARN_ON() within should_
restart_cycle() could be removed.  By doing that, that function becomes
a dummy wrapper on list_is_last() so this patch simply gets rid of it
and call list_is_last() within advance_sched() instead.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
---
 net/sched/sch_taprio.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index d0aae7b5e608..77cca993710a 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -209,14 +209,6 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
 	return NULL;
 }
 
-static bool should_restart_cycle(const struct taprio_sched *q,
-				 const struct sched_entry *entry)
-{
-	WARN_ON(!entry);
-
-	return list_is_last(&entry->list, &q->entries);
-}
-
 static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 {
 	struct taprio_sched *q = container_of(timer, struct taprio_sched,
@@ -240,7 +232,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
 		goto first_run;
 	}
 
-	if (should_restart_cycle(q, entry))
+	if (list_is_last(&entry->list, &q->entries))
 		next = list_first_entry(&q->entries, struct sched_entry,
 					list);
 	else
-- 
2.21.0

[PATCH net-next v2 4/5] net: sched: taprio: Fix taprio_peek()

[Andre Guedes]

While traversing taprio's children qdisc list, if the gate is closed for
a given traffic class, we should continue traversing the list since the
remaining qdiscs may have skb ready for transmission.

This patch also takes this opportunity and changes the function to use
the TAPRIO_ALL_GATES_OPEN macro instead of the magic number '-1'.

Fixes: 5a781ccbd19e (“tc: Add support for configuring the taprio scheduler”)
Signed-off-by: Andre Guedes <andre.guedes@intel.com>
---
 net/sched/sch_taprio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 77cca993710a..0df924f87f3e 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -90,7 +90,7 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch)
 
 	rcu_read_lock();
 	entry = rcu_dereference(q->current_entry);
-	gate_mask = entry ? entry->gate_mask : -1;
+	gate_mask = entry ? entry->gate_mask : TAPRIO_ALL_GATES_OPEN;
 	rcu_read_unlock();
 
 	if (!gate_mask)
@@ -112,7 +112,7 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch)
 		tc = netdev_get_prio_tc_map(dev, prio);
 
 		if (!(gate_mask & BIT(tc)))
-			return NULL;
+			continue;
 
 		return skb;
 	}
-- 
2.21.0

[PATCH net-next v2 5/5] net: sched: taprio: Fix taprio_dequeue()

[Andre Guedes]

In case we don't have 'guard' or 'budget' to transmit the skb, we should
continue traversing the qdisc list since the remaining guard/budget
might be enough to transmit a skb from other children qdiscs.

Fixes: 5a781ccbd19e (“tc: Add support for configuring the taprio scheduler”)
Signed-off-by: Andre Guedes <andre.guedes@intel.com>
---
 net/sched/sch_taprio.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 0df924f87f3e..df848a36b222 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -188,12 +188,12 @@ static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
 		 */
 		if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
 		    ktime_after(guard, entry->close_time))
-			return NULL;
+			continue;
 
 		/* ... and no budget. */
 		if (gate_mask != TAPRIO_ALL_GATES_OPEN &&
 		    atomic_sub_return(len, &entry->budget) < 0)
-			return NULL;
+			continue;
 
 		skb = child->ops->dequeue(child);
 		if (unlikely(!skb))
-- 
2.21.0

Re: [PATCH net-next v2 0/5] Taprio qdisc fixes

[David Miller]

From: Andre Guedes <andre.guedes@intel.com>
Date: Tue, 23 Apr 2019 12:44:19 -0700

> I'm re-sending this series, now with the "net-next" prefix in the subject.
> 
> The only change from the previous version is in patch 3. As suggested by Cong
> Wang, it removes the !entry check within should_restart_cycle() since it is
> already checked by the caller. As a side effect, that function becomes a dummy
> wrapper on list_is_last() so we simply remove it and call list_is_last()
> instead.

Series applied, thanks.