On Tue, Jun 09, 2020 at 09:10:05AM +0530, Harish wrote:
> On systems with large number of cpus, test fails trying to set
> affinity for child process by calling sched_setaffinity() with
> smaller size for cpuset. This patch fixes it by making sure that
> the size of allocated cpu set 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: Harish <har...@linux.ibm.com>
> Signed-off-by: Sandipan Das <sandi...@linux.ibm.com>
> ---
> .../powerpc/benchmarks/context_switch.c | 18 ++++++++++++------
> 1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/tools/testing/selftests/powerpc/benchmarks/context_switch.c
> b/tools/testing/selftests/powerpc/benchmarks/context_switch.c
> index a2e8c9da7fa5..de6c49d6f88f 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) {
> @@ -116,12 +118,16 @@ static void start_process_on(void *(*fn)(void *), void
> *arg, unsigned long cpu)
> if (pid)
> return;
>
> - CPU_ZERO(&cpuset);
> - CPU_SET(cpu, &cpuset);
> + size = CPU_ALLOC_SIZE(ncpus);
> + ncpus = get_nprocs();
above two lines should be interchanged, ncpus not assigned while getting used
to get size.
> + cpuset = CPU_ALLOC(ncpus);
> + 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");
> - exit(1);
> + CPU_FREE(cpuset);
> + exit(-1);
do we need to change the return value here?
probably other framework might rely on previous value?
Regards,
-Satheesh.
> }
>
> fn(arg);
> --
> 2.24.1
>
