On 09/16/2015 12:21 PM, Josh Wu wrote:
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
when when ... could be fixed when applied
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.wu@atmel.com
Acked-by: Andreas Bießmann andreas.devel@googlemail.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