On Wed, Jun 5, 2019 at 10:46 PM Song Liu <songliubraving@xxxxxx> wrote:
>
>
>
> > On Jun 5, 2019, at 4:15 PM, Hechao Li <hechaol@xxxxxx> wrote:
> >
> > Adding a new API libbpf_num_possible_cpus() that helps user with
> > per-CPU map operations.
> >
> > Signed-off-by: Hechao Li <hechaol@xxxxxx>
Your patches didn't get into mailing list. I had this problem before,
for me the issue was fixed by trimming the CC list to a minimum, maybe
try that? You should also probably include netdev@xxxxxxxxxxxxxxx,
btw.
> > ---
> > tools/lib/bpf/libbpf.c | 49 ++++++++++++++++++++++++++++++++++++++++
> > tools/lib/bpf/libbpf.h | 16 +++++++++++++
> > tools/lib/bpf/libbpf.map | 1 +
> > 3 files changed, 66 insertions(+)
> >
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index ba89d9727137..580b14307237 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -3827,3 +3827,52 @@ void bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear)
> > desc->array_offset, addr);
> > }
> > }
> > +
> > +int libbpf_num_possible_cpus(void)
> > +{
> > + static const char *fcpu = "/sys/devices/system/cpu/possible";
> > + static int cpus;
> > + char buf[128];
> > + int len = 0, n = 0, il = 0, ir = 0;
> > + int fd = -1;
> > + unsigned int start = 0, end = 0;
Please sort from longest line length to shortest (so-called "reverse
Christmas tree").
> > +
> > + if (cpus > 0)
> > + return cpus;
> > +
> > + fd = open(fcpu, O_RDONLY);
> > + if (fd < 0) {
> > + pr_warning("Failed to open file %s\n", fcpu);
> > + return -errno;
pr_warning can call into user-specified callback function, which can
perform some actions that will clobber errno variable. So you should
save errno before pr_warning. Also, it's useful to include errno in
error message itself.
> > + }
> > + len = read(fd, buf, sizeof(buf));
> > + close(fd);
> > + if (len <= 0) {
> > + pr_warning("Failed to read number of possible cpus from %s\n",
> > + fcpu);
> > + return -errno;
Same about errno saving.
> > + }
> > + if (len == sizeof(buf)) {
> > + pr_warning("File: %s size overflow\n", fcpu);
> > + return -EOVERFLOW;
> > + }
> > + buf[len] = '\0';
> > +
> > + for (ir = 0, cpus = 0; ir <= len; ir++) {
> > + /* Each sub string separated by ',' has format \d+-\d+ or \d+ */
> > + if (buf[ir] == ',' || buf[ir] == '\0') {
> > + buf[ir] = '\0';
> > + n = sscanf(&buf[il], "%u-%u", &start, &end);
> > + if (n <= 0) {
> > + pr_warning("Failed to get # CPUs from %s\n",
> > + &buf[il]);
> > + return -EINVAL;
> > + } else if (n == 1) {
> > + end = start;
> > + }
> > + cpus += end - start + 1;
> > + il = ir + 1;
> > + }
> > + }
> > + return cpus;
> > +}
> > diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
> > index 1af0d48178c8..f5e82eb2e5d4 100644
> > --- a/tools/lib/bpf/libbpf.h
> > +++ b/tools/lib/bpf/libbpf.h
> > @@ -454,6 +454,22 @@ bpf_program__bpil_addr_to_offs(struct bpf_prog_info_linear *info_linear);
> > LIBBPF_API void
> > bpf_program__bpil_offs_to_addr(struct bpf_prog_info_linear *info_linear);
> >
> > +/*
> > + * A helper function to get the number of possible CPUs before looking up
> > + * per-CPU maps. Negative errno is returned on failure.
> > + *
> > + * Example usage:
> > + *
> > + * int ncpus = libbpf_num_possible_cpus();
> > + * if (ncpus <= 0) {
> > + * // error handling
> > + * }
> > + * long values[ncpus];
> > + * bpf_map_lookup_elem(per_cpu_map_fd, key, values);
> > + *
> > + */
> > +LIBBPF_API int libbpf_num_possible_cpus(void);
> > +
> > #ifdef __cplusplus
> > } /* extern "C" */
> > #endif
> > diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
> > index 46dcda89df21..7f76d19cb02b 100644
> > --- a/tools/lib/bpf/libbpf.map
> > +++ b/tools/lib/bpf/libbpf.map
> > @@ -172,4 +172,5 @@ LIBBPF_0.0.4 {
> > btf_dump__new;
> > btf__parse_elf;
> > bpf_object__load_xattr;
> > + libbpf_num_possible_cpus;
>
> Please indent with tab instead of space.
>
> Thanks,
> Song
>
> > } LIBBPF_0.0.3;
> > --
> > 2.17.1
> >
>
