On Tue, Jun 09, 2020 at 01:44:23PM +0530, Harish wrote:
> On systems with large number of cpus, test fails trying to set
> affinity by calling sched_setaffinity() with smaller size for
> affinity mask. This patch fixes it by making sure that the size of
> allocated affinity mask is dependent on the number of CPUs as
> reported by get_nprocs().
>
> Fixes: 00b7ec5c9cf3 ("selftests/powerpc: Import Anton's context_switch2
> benchmark")
> Reported-by: Shirisha Ganta <shiga...@in.ibm.com>
> Signed-off-by: Sandipan Das <sandi...@linux.ibm.com>
> Signed-off-by: Harish <har...@linux.ibm.com>
> ---
Reviewed-by: Satheesh Rajendran <sathn...@linux.vnet.ibm.com>
> v2:
> https://lore.kernel.org/linuxppc-dev/20200609034005.520137-1-har...@linux.ibm.com/
>
> Changes from v2:
> - Interchanged size and ncpus as suggested by Satheesh
> - Revert the exit code as suggested by Satheesh
> - Added NULL check for the affinity mask as suggested by Kamalesh
> - Freed the affinity mask allocation after affinity is set
> as suggested by Kamalesh
> - Changed "cpu set" to "affinity mask" in the commit message
>
> ---
> .../powerpc/benchmarks/context_switch.c | 21 ++++++++++++++-----
> 1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/powerpc/benchmarks/context_switch.c
> b/tools/testing/selftests/powerpc/benchmarks/context_switch.c
> index a2e8c9da7fa5..d50cc05df495 100644
> --- a/tools/testing/selftests/powerpc/benchmarks/context_switch.c
> +++ b/tools/testing/selftests/powerpc/benchmarks/context_switch.c
> @@ -19,6 +19,7 @@
> #include <limits.h>
> #include <sys/time.h>
> #include <sys/syscall.h>
> +#include <sys/sysinfo.h>
> #include <sys/types.h>
> #include <sys/shm.h>
> #include <linux/futex.h>
> @@ -104,8 +105,9 @@ static void start_thread_on(void *(*fn)(void *), void
> *arg, unsigned long cpu)
>
> static void start_process_on(void *(*fn)(void *), void *arg, unsigned long
> cpu)
> {
> - int pid;
> - cpu_set_t cpuset;
> + int pid, ncpus;
> + cpu_set_t *cpuset;
> + size_t size;
>
> pid = fork();
> if (pid == -1) {
> @@ -116,14 +118,23 @@ static void start_process_on(void *(*fn)(void *), void
> *arg, unsigned long cpu)
> if (pid)
> return;
>
> - CPU_ZERO(&cpuset);
> - CPU_SET(cpu, &cpuset);
> + ncpus = get_nprocs();
> + size = CPU_ALLOC_SIZE(ncpus);
> + cpuset = CPU_ALLOC(ncpus);
> + if (!cpuset) {
> + perror("malloc");
> + exit(1);
> + }
> + CPU_ZERO_S(size, cpuset);
> + CPU_SET_S(cpu, size, cpuset);
>
> - if (sched_setaffinity(0, sizeof(cpuset), &cpuset)) {
> + if (sched_setaffinity(0, size, cpuset)) {
> perror("sched_setaffinity");
> + CPU_FREE(cpuset);
> exit(1);
> }
>
> + CPU_FREE(cpuset);
> fn(arg);
>
> exit(0);
> --
> 2.24.1
>
