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

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Message-Id: <20171114192702.31193-3-sthemmin@microsoft.com>
Date:   Tue, 14 Nov 2017 11:27:02 -0800
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     stephen@...workplumber.org, jhs@...atatu.com,
        xiyou.wangcong@...il.com, jiri@...nulli.us, davem@...emloft.net
Cc:     netdev@...r.kernel.org, Stephen Hemminger <sthemmin@...rosoft.com>
Subject: [PATCH net-next v2 2/2] netem: remove unnecessary 64 bit modulus

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@...radead.org>
Signed-off-by: Stephen Hemminger <stephen@...workplumber.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