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
Bießmann. Thanks them a lot.
Signed-off-by: Josh Wu <josh...@atmel.com>
---
Changes in v2:
- left shift and add the getpid() value instead of removing it.
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 bf9d935..5fa3e0c 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
--
1.9.1
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