On Wed, Sep 22, 2021 at 2:22 PM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote: > > On 9/22/21 9:07 AM, Muhammad Falak R Wani wrote: > > Simplify libbpf_num_possible_cpus by using sysconf(_SC_NPROCESSORS_CONF) > > instead of parsing a file. > > This patch is a part ([0]) of libbpf-1.0 milestone. > > > > [0] Closes: https://github.com/libbpf/libbpf/issues/383 > > > > Signed-off-by: Muhammad Falak R Wani <falakreyaz@xxxxxxxxx> > > --- > > tools/lib/bpf/libbpf.c | 17 ++++------------- > > 1 file changed, 4 insertions(+), 13 deletions(-) > > > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > > index ef5db34bf913..f1c0abe5b58d 100644 > > --- a/tools/lib/bpf/libbpf.c > > +++ b/tools/lib/bpf/libbpf.c > > @@ -10898,25 +10898,16 @@ int parse_cpu_mask_file(const char *fcpu, bool **mask, int *mask_sz) > > > > int libbpf_num_possible_cpus(void) > > { > > - static const char *fcpu = "/sys/devices/system/cpu/possible"; > > static int cpus; > > - int err, n, i, tmp_cpus; > > - bool *mask; > > + int tmp_cpus; > > > > tmp_cpus = READ_ONCE(cpus); > > if (tmp_cpus > 0) > > return tmp_cpus; > > > > - err = parse_cpu_mask_file(fcpu, &mask, &n); > > - if (err) > > - return libbpf_err(err); > > - > > - tmp_cpus = 0; > > - for (i = 0; i < n; i++) { > > - if (mask[i]) > > - tmp_cpus++; > > - } > > - free(mask); > > + tmp_cpus = sysconf(_SC_NPROCESSORS_CONF); > > + if (tmp_cpus < 1) > > + return libbpf_err(-EINVAL); > > This approach is unfortunately broken, see also commit e00c7b216f34 ("bpf: fix > multiple issues in selftest suite and samples") for more details: Oh, that predates me. Thanks, Daniel! Sorry, Muhammad, seems like current implementation is there for a reason and will have to stay. Thanks a lot for working on this, though. Hopefully you can help with other issues, though. [...] > > Thanks, > Daniel > > > WRITE_ONCE(cpus, tmp_cpus); > > return tmp_cpus; > > >
