[PATCH net-next v2 0/2] netem: fix compilation on 32 bit

[PATCH net-next v2 0/2] netem: fix compilation on 32 bit

[Stephen Hemminger]

A couple of places where 64 bit CPU was being assumed incorrectly.

Stephen Hemminger (2):
  netem: fix 64 bit divide
  netem: remove unnecessary 64 bit modulus

 net/sched/sch_netem.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

-- 
2.11.0

[PATCH net-next v2 1/2] netem: use 64 bit divide by rate

[Stephen Hemminger]

Since times are now expressed in nanosecond, need to now do
true 64 bit divide. Old code would truncate rate at 32 bits.
Rename function to better express current usage.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 net/sched/sch_netem.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index b686e755fda9..644323d6081c 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -339,10 +339,8 @@ static s64 tabledist(s64 mu, s64 sigma,
 	return  x / NETEM_DIST_SCALE + (sigma / NETEM_DIST_SCALE) * t + mu;
 }
 
-static u64 packet_len_2_sched_time(unsigned int len,
-				   struct netem_sched_data *q)
+static u64 packet_time_ns(u64 len, const struct netem_sched_data *q)
 {
-	u64 offset;
 	len += q->packet_overhead;
 
 	if (q->cell_size) {
@@ -352,9 +350,8 @@ static u64 packet_len_2_sched_time(unsigned int len,
 			cells++;
 		len = cells * (q->cell_size + q->cell_overhead);
 	}
-	offset = (u64)len * NSEC_PER_SEC;
-	do_div(offset, q->rate);
-	return offset;
+
+	return div64_u64(len * NSEC_PER_SEC, q->rate);
 }
 
 static void tfifo_reset(struct Qdisc *sch)
@@ -556,7 +553,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
 				now = last->time_to_send;
 			}
 
-			delay += packet_len_2_sched_time(qdisc_pkt_len(skb), q);
+			delay += packet_time_ns(qdisc_pkt_len(skb), q);
 		}
 
 		cb->time_to_send = now + delay;
-- 
2.11.0

[PATCH net-next v2 2/2] netem: remove unnecessary 64 bit modulus

[Stephen Hemminger]

Fix compilation on 32 bit platforms (where doing modulus operation
with 64 bit requires extra glibc functions) by truncation.
The jitter for table distribution is limited to a 32 bit value
because random numbers are scaled as 32 bit value.

Also fix some whitespace.

Fixes: 99803171ef04 ("netem: add uapi to express delay and jitter in nanoseconds")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 net/sched/sch_netem.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 644323d6081c..dd70924cbcdf 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -312,9 +312,9 @@ static bool loss_event(struct netem_sched_data *q)
  * std deviation sigma.  Uses table lookup to approximate the desired
  * distribution, and a uniformly-distributed pseudo-random source.
  */
-static s64 tabledist(s64 mu, s64 sigma,
+static s64 tabledist(s64 mu, s32 sigma,
 		     struct crndstate *state,
-			 const struct disttable *dist)
+		     const struct disttable *dist)
 {
 	s64 x;
 	long t;
@@ -327,7 +327,7 @@ static s64 tabledist(s64 mu, s64 sigma,
 
 	/* default uniform distribution */
 	if (dist == NULL)
-		return (rnd % (2*sigma)) - sigma + mu;
+		return (rnd % (2 * sigma)) - sigma + mu;
 
 	t = dist->table[rnd % dist->size];
 	x = (sigma % NETEM_DIST_SCALE) * t;
-- 
2.11.0

Re: [PATCH net-next v2 0/2] netem: fix compilation on 32 bit

[Randy Dunlap]

On 11/14/2017 11:27 AM, Stephen Hemminger wrote:
> A couple of places where 64 bit CPU was being assumed incorrectly.
> 
> Stephen Hemminger (2):
>   netem: fix 64 bit divide
>   netem: remove unnecessary 64 bit modulus
> 
>  net/sched/sch_netem.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> 

Acked-by: Randy Dunlap <rdunlap@infradead.org>

Thanks.

-- 
~Randy

Re: [PATCH net-next v2 0/2] netem: fix compilation on 32 bit

[Dave Taht]

On Tue, Nov 14, 2017 at 11:40 AM, Randy Dunlap <rdunlap@infradead.org> wrote:
> On 11/14/2017 11:27 AM, Stephen Hemminger wrote:
>> A couple of places where 64 bit CPU was being assumed incorrectly.
>>
>> Stephen Hemminger (2):
>>   netem: fix 64 bit divide
>>   netem: remove unnecessary 64 bit modulus
>>
>>  net/sched/sch_netem.c | 17 +++++++----------
>>  1 file changed, 7 insertions(+), 10 deletions(-)
>>
>
> Acked-by: Randy Dunlap <rdunlap@infradead.org>

Acked-by: Dave Taht <dave.taht@gmail.com>

Thx.

Re: [net-next,v2,0/2] netem: fix compilation on 32 bit

[James Hogan]

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On Tue, Nov 14, 2017 at 11:27:00AM -0800, Stephen Hemminger wrote:
> A couple of places where 64 bit CPU was being assumed incorrectly.
> 
> Stephen Hemminger (2):
>   netem: fix 64 bit divide
>   netem: remove unnecessary 64 bit modulus
> 
>  net/sched/sch_netem.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
> Acked-by: Randy Dunlap <rdunlap@infradead.org>
> Acked-by: Dave Taht <dave.taht@gmail.com>

These appears to fix the MIPS build, so

Tested-by: James Hogan <jhogan@kernel.org>

Thanks
James

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Re: [PATCH net-next v2 0/2] netem: fix compilation on 32 bit

[David Miller]

From: Stephen Hemminger <stephen@networkplumber.org>
Date: Tue, 14 Nov 2017 11:27:00 -0800

> A couple of places where 64 bit CPU was being assumed incorrectly.

Series applied, thanks.