netdev - Re: [PATCH net-next 3/5] net/sched: taprio: fix build without 64bit div

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Date:   Mon, 29 Apr 2019 17:04:21 -0700
From:   Leandro Dorileo <l@...ileo.org>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>, davem@...emloft.net
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>,
        Leandro Dorileo <leandro.maciel.dorileo@...el.com>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>
Subject: Re: [PATCH net-next 3/5] net/sched: taprio: fix build without 64bit div


Hi,

Jakub Kicinski <jakub.kicinski@...ronome.com> writes:

> Recent changes to taprio did not use the correct div64 helpers,
> leading to:
>
> net/sched/sch_taprio.o: In function `taprio_dequeue':
> sch_taprio.c:(.text+0x34a): undefined reference to `__divdi3'
> net/sched/sch_taprio.o: In function `advance_sched':
> sch_taprio.c:(.text+0xa0b): undefined reference to `__divdi3'
> net/sched/sch_taprio.o: In function `taprio_init':
> sch_taprio.c:(.text+0x1450): undefined reference to `__divdi3'
> /home/jkicinski/devel/linux/Makefile:1032: recipe for target 'vmlinux' failed
>
> Use math64 helpers.
>
> Fixes: 7b9eba7ba0c1 ("net/sched: taprio: fix picos_per_byte miscalculation")
> Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
> Reviewed-by: Dirk van der Merwe <dirk.vandermerwe@...ronome.com>


Acked-by: Leandro Dorileo <leandro.maciel.dorileo@...el.com>


> ---
> CC: Leandro Dorileo <leandro.maciel.dorileo@...el.com>
> CC: Vinicius Costa Gomes <vinicius.gomes@...el.com>
>
>  net/sched/sch_taprio.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/net/sched/sch_taprio.c b/net/
> sched/sch_taprio.c
> index 1b0fb80162e6..001182aa3959 100644
> --- a/net/sched/sch_taprio.c
> +++ b/net/sched/sch_taprio.c
> @@ -13,6 +13,7 @@
>  #include <linux/list.h>
>  #include <linux/errno.h>
>  #include <linux/skbuff.h>
> +#include <linux/math64.h>
>  #include <linux/module.h>
>  #include <linux/spinlock.h>
>  #include <net/netlink.h>
> @@ -121,7 +122,14 @@ static struct sk_buff *taprio_peek(struct Qdisc *sch)
>  
>  static inline int length_to_duration(struct taprio_sched *q, int len)
>  {
> -	return (len * atomic64_read(&q->picos_per_byte)) / 1000;
> +	return div_u64(len * atomic64_read(&q->picos_per_byte), 1000);
> +}
> +
> +static void taprio_set_budget(struct taprio_sched *q, struct sched_entry *entry)
> +{
> +	atomic_set(&entry->budget,
> +		   div64_u64((u64)entry->interval * 1000,
> +			     atomic64_read(&q->picos_per_byte)));
>  }
>  
>  static struct sk_buff *taprio_dequeue(struct Qdisc *sch)
> @@ -241,8 +249,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
>  	close_time = k
> time_add_ns(entry->close_time, next->interval);
>  
>  	next->close_time = close_time;
> -	atomic_set(&next->budget,
> -		   (next->interval * 1000) / atomic64_read(&q->picos_per_byte));
> +	taprio_set_budget(q, next);
>  
>  first_run:
>  	rcu_assign_pointer(q->current_entry, next);
> @@ -575,9 +582,7 @@ static void taprio_start_sched(struct Qdisc *sch, ktime_t start)
>  				 list);
>  
>  	first->close_time = ktime_add_ns(start, first->interval);
> -	atomic_set(&first->budget,
> -		   (first->interval * 1000) /
> -		   atomic64_read(&q->picos_per_byte));
> +	taprio_set_budget(q, first);
>  	rcu_assign_pointer(q->current_entry, NULL);
>  
>  	spin_unlock_irqrestore(&q->current_entry_lock, flags);
> -- 
> 2.21.0