linux-kernel - Re: [PATCH 4/4] perf bench: Fix div-by-zero if runtime is zero

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Date:   Mon, 20 Apr 2020 11:05:26 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Tommi Rantala <tommi.t.rantala@...ia.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Darren Hart <dvhart@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] perf bench: Fix div-by-zero if runtime is zero

On Fri, Apr 17, 2020 at 04:23:29PM +0300, Tommi Rantala wrote:
> Fix div-by-zero if runtime is zero:
> 
>   $ perf bench futex hash --runtime=0
>   # Running 'futex/hash' benchmark:
>   Run summary [PID 12090]: 4 threads, each operating on 1024 [private] futexes for 0 secs.
>   Floating point exception (core dumped)
> 
> Signed-off-by: Tommi Rantala <tommi.t.rantala@...ia.com>

Acked-by: Jiri Olsa <jolsa@...hat.com>

thanks,
jirka

> ---
>  tools/perf/bench/epoll-wait.c    | 3 ++-
>  tools/perf/bench/futex-hash.c    | 3 ++-
>  tools/perf/bench/futex-lock-pi.c | 3 ++-
>  3 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/bench/epoll-wait.c b/tools/perf/bench/epoll-wait.c
> index f938c585d512..cf797362675b 100644
> --- a/tools/perf/bench/epoll-wait.c
> +++ b/tools/perf/bench/epoll-wait.c
> @@ -519,7 +519,8 @@ int bench_epoll_wait(int argc, const char **argv)
>  		qsort(worker, nthreads, sizeof(struct worker), cmpworker);
>  
>  	for (i = 0; i < nthreads; i++) {
> -		unsigned long t = worker[i].ops / bench__runtime.tv_sec;
> +		unsigned long t = bench__runtime.tv_sec > 0 ?
> +			worker[i].ops / bench__runtime.tv_sec : 0;
>  
>  		update_stats(&throughput_stats, t);
>  
> diff --git a/tools/perf/bench/futex-hash.c b/tools/perf/bench/futex-hash.c
> index 65eebe06c04d..915bf3da7ce2 100644
> --- a/tools/perf/bench/futex-hash.c
> +++ b/tools/perf/bench/futex-hash.c
> @@ -205,7 +205,8 @@ int bench_futex_hash(int argc, const char **argv)
>  	pthread_mutex_destroy(&thread_lock);
>  
>  	for (i = 0; i < nthreads; i++) {
> -		unsigned long t = worker[i].ops / bench__runtime.tv_sec;
> +		unsigned long t = bench__runtime.tv_sec > 0 ?
> +			worker[i].ops / bench__runtime.tv_sec : 0;
>  		update_stats(&throughput_stats, t);
>  		if (!silent) {
>  			if (nfutexes == 1)
> diff --git a/tools/perf/bench/futex-lock-pi.c b/tools/perf/bench/futex-lock-pi.c
> index 89fd8f325f38..bb25d8beb3b8 100644
> --- a/tools/perf/bench/futex-lock-pi.c
> +++ b/tools/perf/bench/futex-lock-pi.c
> @@ -211,7 +211,8 @@ int bench_futex_lock_pi(int argc, const char **argv)
>  	pthread_mutex_destroy(&thread_lock);
>  
>  	for (i = 0; i < nthreads; i++) {
> -		unsigned long t = worker[i].ops / bench__runtime.tv_sec;
> +		unsigned long t = bench__runtime.tv_sec > 0 ?
> +			worker[i].ops / bench__runtime.tv_sec : 0;
>  
>  		update_stats(&throughput_stats, t);
>  		if (!silent)
> -- 
> 2.25.2
>