linux-kernel - Re: [PATCH] selftests/bpf: Make bpf_util work on uniprocessor systems

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Date:   Fri, 8 Sep 2017 16:01:57 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Thomas Meyer <thomas@...3r.de>
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        shuah@...nel.org, Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH] selftests/bpf: Make bpf_util work on uniprocessor systems

On Fri, Sep 08, 2017 at 01:19:23PM +0200, Thomas Meyer wrote:
> The current implementation fails to work on uniprocessor systems.
> Fix the parser to also handle the uniprocessor case.
> 
> Signed-off-by: Thomas Meyer <thomas@...3r.de>

Thanks for the fix. lgtm
Acked-by: Alexei Starovoitov <ast@...nel.org>

This time it's ok to go via selftest tree, but next time please use net-next/net
to avoid conflicts.
Thanks

> ---
>  tools/testing/selftests/bpf/bpf_util.h | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
> index 20ecbaa0d85d..6c53a8906eff 100644
> --- a/tools/testing/selftests/bpf/bpf_util.h
> +++ b/tools/testing/selftests/bpf/bpf_util.h
> @@ -12,6 +12,7 @@ static inline unsigned int bpf_num_possible_cpus(void)
>  	unsigned int start, end, possible_cpus = 0;
>  	char buff[128];
>  	FILE *fp;
> +	int n;
>  
>  	fp = fopen(fcpu, "r");
>  	if (!fp) {
> @@ -20,17 +21,17 @@ static inline unsigned int bpf_num_possible_cpus(void)
>  	}
>  
>  	while (fgets(buff, sizeof(buff), fp)) {
> -		if (sscanf(buff, "%u-%u", &start, &end) == 2) {
> -			possible_cpus = start == 0 ? end + 1 : 0;
> -			break;
> +		n = sscanf(buff, "%u-%u", &start, &end);
> +		if (n == 0) {
> +			printf("Failed to retrieve # possible CPUs!\n");
> +			exit(1);
> +		} else if (n == 1) {
> +			end = start;
>  		}
> +		possible_cpus = start == 0 ? end + 1 : 0;
> +		break;
>  	}
> -
>  	fclose(fp);
> -	if (!possible_cpus) {
> -		printf("Failed to retrieve # possible CPUs!\n");
> -		exit(1);
> -	}
>  
>  	return possible_cpus;
>  }
> -- 
> 2.11.0
>