[ My reply somehow rejected by netdev, this is to send it again. ]
On Wed, Jan 30, 2019 at 1:19 AM Martynas Pumputis <m...@lambda.lt> wrote:
>
> Previously, bpf_num_possible_cpus() had a bug when calculating a
> number of possible CPUs in the case of sparse CPU allocations, as
> it was considering only the first range or element of
> /sys/devices/system/cpu/possible.
>
> E.g. in the case of "0,2-3" (CPU 1 is not available), the function
> returned 1 instead of 3.
>
> This patch fixes the function by making it parse all CPU ranges and
> elements.
>
> Signed-off-by: Martynas Pumputis <m...@lambda.lt>
> ---
> tools/testing/selftests/bpf/bpf_util.h | 29 +++++++++++++++++---------
> 1 file changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/bpf_util.h
> b/tools/testing/selftests/bpf/bpf_util.h
> index 315a44fa32af..8cab50408204 100644
> --- a/tools/testing/selftests/bpf/bpf_util.h
> +++ b/tools/testing/selftests/bpf/bpf_util.h
> @@ -13,7 +13,7 @@ static inline unsigned int bpf_num_possible_cpus(void)
> unsigned int start, end, possible_cpus = 0;
> char buff[128];
> FILE *fp;
> - int n;
> + int n, i, j = 0;
>
> fp = fopen(fcpu, "r");
> if (!fp) {
> @@ -21,17 +21,26 @@ static inline unsigned int bpf_num_possible_cpus(void)
> exit(1);
> }
>
> - while (fgets(buff, sizeof(buff), fp)) {
> - 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;
> + if (!fgets(buff, sizeof(buff), fp)) {
> + printf("Failed to read %s!\n", fcpu);
> + exit(1);
> + }
> +
> + for (i = 0; i <= strlen(buff); i++) {
> + if (buff[i] == ',' || buff[i] == '\0') {
> + buff[i] = '\0';
This does not sound right. For example, the cpu list "0,2-3",
you will change "," to '\0" so buffer becomes "0\02-3".
The next iteration you will get strlen(buff) = 1.
The "2-3" will be skipped.
> + n = sscanf(&buff[j], "%u-%u", &start, &end);
> + if (n <= 0) {
> + printf("Failed to retrieve # possible
> CPUs!\n");
> + exit(1);
> + } else if (n == 1) {
> + end = start;
> + }
> + possible_cpus += end - start + 1;
> + j = i + 1;
> }
> - possible_cpus = start == 0 ? end + 1 : 0;
> - break;
> }
> +
> fclose(fp);
>
> return possible_cpus;
> --
> 2.20.1
>
