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    Subject[PATCH 5.4 145/309] selftests/bpf: Fix perf_buffer test on systems w/ offline CPUs
    Date
    From: Andrii Nakryiko <andriin@fb.com>

    commit 91cbdf740a476cf2c744169bf407de2e3ac1f3cf upstream.

    Fix up perf_buffer.c selftest to take into account offline/missing CPUs.

    Fixes: ee5cf82ce04a ("selftests/bpf: test perf buffer API")
    Signed-off-by: Andrii Nakryiko <andriin@fb.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Link: https://lore.kernel.org/bpf/20191212013621.1691858-1-andriin@fb.com
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    tools/testing/selftests/bpf/prog_tests/perf_buffer.c | 29 +++++++++++++++----
    1 file changed, 24 insertions(+), 5 deletions(-)

    --- a/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
    +++ b/tools/testing/selftests/bpf/prog_tests/perf_buffer.c
    @@ -4,6 +4,7 @@
    #include <sched.h>
    #include <sys/socket.h>
    #include <test_progs.h>
    +#include "libbpf_internal.h"

    static void on_sample(void *ctx, int cpu, void *data, __u32 size)
    {
    @@ -19,7 +20,7 @@ static void on_sample(void *ctx, int cpu

    void test_perf_buffer(void)
    {
    - int err, prog_fd, nr_cpus, i, duration = 0;
    + int err, prog_fd, on_len, nr_on_cpus = 0, nr_cpus, i, duration = 0;
    const char *prog_name = "kprobe/sys_nanosleep";
    const char *file = "./test_perf_buffer.o";
    struct perf_buffer_opts pb_opts = {};
    @@ -29,15 +30,27 @@ void test_perf_buffer(void)
    struct bpf_object *obj;
    struct perf_buffer *pb;
    struct bpf_link *link;
    + bool *online;

    nr_cpus = libbpf_num_possible_cpus();
    if (CHECK(nr_cpus < 0, "nr_cpus", "err %d\n", nr_cpus))
    return;

    + err = parse_cpu_mask_file("/sys/devices/system/cpu/online",
    + &online, &on_len);
    + if (CHECK(err, "nr_on_cpus", "err %d\n", err))
    + return;
    +
    + for (i = 0; i < on_len; i++)
    + if (online[i])
    + nr_on_cpus++;
    +
    /* load program */
    err = bpf_prog_load(file, BPF_PROG_TYPE_KPROBE, &obj, &prog_fd);
    - if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno))
    - return;
    + if (CHECK(err, "obj_load", "err %d errno %d\n", err, errno)) {
    + obj = NULL;
    + goto out_close;
    + }

    prog = bpf_object__find_program_by_title(obj, prog_name);
    if (CHECK(!prog, "find_probe", "prog '%s' not found\n", prog_name))
    @@ -64,6 +77,11 @@ void test_perf_buffer(void)
    /* trigger kprobe on every CPU */
    CPU_ZERO(&cpu_seen);
    for (i = 0; i < nr_cpus; i++) {
    + if (i >= on_len || !online[i]) {
    + printf("skipping offline CPU #%d\n", i);
    + continue;
    + }
    +
    CPU_ZERO(&cpu_set);
    CPU_SET(i, &cpu_set);

    @@ -81,8 +99,8 @@ void test_perf_buffer(void)
    if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
    goto out_free_pb;

    - if (CHECK(CPU_COUNT(&cpu_seen) != nr_cpus, "seen_cpu_cnt",
    - "expect %d, seen %d\n", nr_cpus, CPU_COUNT(&cpu_seen)))
    + if (CHECK(CPU_COUNT(&cpu_seen) != nr_on_cpus, "seen_cpu_cnt",
    + "expect %d, seen %d\n", nr_on_cpus, CPU_COUNT(&cpu_seen)))
    goto out_free_pb;

    out_free_pb:
    @@ -91,4 +109,5 @@ out_detach:
    bpf_link__destroy(link);
    out_close:
    bpf_object__close(obj);
    + free(online);
    }

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