Oops, thanks for noticing the issue with strlen in the for loop. Changing to "int len = strlen(buff); for (i = 0; i < len; i++) <..>" should fix the issue. I'm going to re-submit the patch.
Also, I put some testing results: https://gist.github.com/brb/5369b5cfd08babb80cf2c4081dc19762 On Thu, Jan 31, 2019, at 7:25 AM, Y Song wrote: > [ 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 > >
