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    Subject[PATCH 4.19 093/149] bpf, selftests: fix handling of sparse CPU allocations
    Date
    4.19-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit 1bb54c4071f585ebef56ce8fdfe6026fa2cbcddd ]

    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>
    Acked-by: Yonghong Song <yhs@fb.com>
    Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    tools/testing/selftests/bpf/bpf_util.h | 30 +++++++++++++++++---------
    1 file changed, 20 insertions(+), 10 deletions(-)

    diff --git a/tools/testing/selftests/bpf/bpf_util.h b/tools/testing/selftests/bpf/bpf_util.h
    index 315a44fa32af..84fd6f1bf33e 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 len, n, i, j = 0;

    fp = fopen(fcpu, "r");
    if (!fp) {
    @@ -21,17 +21,27 @@ 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);
    + }
    +
    + len = strlen(buff);
    + for (i = 0; i <= len; i++) {
    + if (buff[i] == ',' || buff[i] == '\0') {
    + buff[i] = '\0';
    + 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;
    --
    2.19.1


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