[PATCH v2] selftests: powerpc: Fix CPU affinity for child process

[Harish]

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();
+       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);
        }
 
        fn(arg);
-- 
2.24.1