From 3e4dad50320d20894710276eb09f2057c6985065 Mon Sep 17 00:00:00 2001
From: Josh Wu <josh.wu@atmel.com>
Date: Wed, 16 Sep 2015 18:21:04 +0800
Subject: [PATCH] tools: gen_eth_addr: add getpid() to time(0) to avoid
duplicated seed
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As 'time(0) | getpid()' will have a lot of duplicated value. It is not a
expected behavior. We expect different value for the seed when when run
it in many times.
So this patch will left shift the getpid() and add to time(0). That
avoid duplicated value.
Test command is like:
% RUN=0; while [ $RUN -lt 10000 ]; do
tools/gen_eth_addr; RUN=$(($RUN+1)); done | sort | uniq | wc -l
10000
This patch is incorporated with suggestions made by Wolfgang Denk and Andreas
BieÃmann. Thanks them a lot.
Signed-off-by: Josh Wu <josh.wu@atmel.com>
Acked-by: Andreas BieÃmann <andreas.devel@googlemail.com>
Acked-by: Wolfgang Denk <wd@denx.de>
Tested-by: Wolfgang Denk <wd@denx.de>
---
tools/gen_eth_addr.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/tools/gen_eth_addr.c b/tools/gen_eth_addr.c
index bf9d935efd..5fa3e0cf56 100644
--- a/tools/gen_eth_addr.c
+++ b/tools/gen_eth_addr.c
@@ -15,7 +15,7 @@ main(int argc, char *argv[])
{
unsigned long ethaddr_low, ethaddr_high;
- srand(time(0) | getpid());
+ srand(time(0) + (getpid() << 8));
/*
* setting the 2nd LSB in the most significant byte of
--
2.39.5