Re: [PATCH v2 net 5/7] net/sched: taprio: fix delayed switching to new schedule after timer expiry
From: Vladimir Oltean <vladimir.oltean@nxp.com>
Date: 2023-11-09 11:51:01
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On Tue, Nov 07, 2023 at 06:20:21AM -0500, Faizal Rahim wrote:
If a new GCL is triggered and the new admin base time falls before the
expiry of advance_timer (current running entry from oper),
taprio_start_sched() resets the current advance_timer expiry to the
new admin base time. However, upon expiry, advance_sched() doesn't
immediately switch to the admin schedule. It continues running entries
from the old oper schedule, and only switches to the new admin schedule
much later. Ideally, if the advance_timer is shorten to align with the
new admin base time, when the timer expires, advance_sched() should
trigger switch_schedules() at the beginning.
To resolve this issue, set the cycle_time_correction to a non-initialized
value in taprio_start_sched(). advance_sched() will use it to initiate
switch_schedules() at the beginning.
Fixes: a3d43c0d56f1 ("taprio: Add support adding an admin schedule")Did the commit you blame really introduce this issue, or was it your rework to trigger switch_schedules() based on the correction?
quoted hunk ↗ jump to hunk
Signed-off-by: Faizal Rahim <redacted> --- net/sched/sch_taprio.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c index f18a5fe12f0c..01b114edec30 100644 --- a/net/sched/sch_taprio.c +++ b/net/sched/sch_taprio.c@@ -1379,14 +1379,19 @@ static void setup_first_end_time(struct taprio_sched *q, } static void taprio_start_sched(struct Qdisc *sch, - ktime_t start, struct sched_gate_list *new) + ktime_t new_base_time, + struct sched_gate_list *new) { struct taprio_sched *q = qdisc_priv(sch); - ktime_t expires; + struct sched_gate_list *oper = NULL; + ktime_t expires, start; if (FULL_OFFLOAD_IS_ENABLED(q->flags)) return; + oper = rcu_dereference_protected(q->oper_sched, + lockdep_is_held(&q->current_entry_lock)); + expires = hrtimer_get_expires(&q->advance_timer); if (expires == 0) expires = KTIME_MAX;@@ -1395,7 +1400,17 @@ static void taprio_start_sched(struct Qdisc *sch, * reprogram it to the earliest one, so we change the admin * schedule to the operational one at the right time. */ - start = min_t(ktime_t, start, expires); + start = min_t(ktime_t, new_base_time, expires); + + if (expires != KTIME_MAX && + ktime_compare(start, new_base_time) == 0) { + /* Since timer was changed to align to the new admin schedule, + * setting the variable below to a non-initialized value will
I find the wording "setting the variable below to a non-initialized value" confusing. 0 is non-initialized? You're talking about a value different than INIT_CYCLE_TIME_CORRECTION. What about "setting a specific cycle correction will indicate ..."?
+ * indicate to advance_sched() to call switch_schedules() after + * this timer expires. + */ + oper->cycle_time_correction = 0;
Why 0 and not ktime_sub(new_base_time, oper->cycle_end_time)? Doesn't the precise correction value make a difference?
+ } hrtimer_start(&q->advance_timer, start, HRTIMER_MODE_ABS); } -- 2.25.1