From 8599099f0c58cec677a47c968e777eee8d64fb80 Mon Sep 17 00:00:00 2001 From: Andre Guedes Date: Tue, 23 Apr 2019 12:44:21 -0700 Subject: [PATCH] net: sched: taprio: Refactor taprio_get_start_time() 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 Signed-off-by: David S. Miller --- 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); -- 2.30.2