selftests/powerpc: context_switch: Fix pthread errors

Turns out pthreads returns an errno and doesn't set errno. This doesn't
play well with perror().

Signed-off-by: Cyril Bur <cyrilbur@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

tools/testing/selftests/powerpc/benchmarks/context_switch.c

@@ -10,6 +10,7 @@
  */
 
 #define _GNU_SOURCE
+#include <errno.h>
 #include <sched.h>
 #include <string.h>
 #include <stdio.h>
@@ -75,6 +76,7 @@ static void touch(void)
 
 static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
 {
+	int rc;
 	pthread_t tid;
 	cpu_set_t cpuset;
 	pthread_attr_t attr;
@@ -82,14 +84,23 @@ static void start_thread_on(void *(*fn)(void *), void *arg, unsigned long cpu)
 	CPU_ZERO(&cpuset);
 	CPU_SET(cpu, &cpuset);
 
-	pthread_attr_init(&attr);
+	rc = pthread_attr_init(&attr);
+	if (rc) {
+		errno = rc;
+		perror("pthread_attr_init");
+		exit(1);
+	}
 
-	if (pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset)) {
+	rc = pthread_attr_setaffinity_np(&attr, sizeof(cpu_set_t), &cpuset);
+	if (rc)	{
+		errno = rc;
 		perror("pthread_attr_setaffinity_np");
 		exit(1);
 	}
 
-	if (pthread_create(&tid, &attr, fn, arg)) {
+	rc = pthread_create(&tid, &attr, fn, arg);
+	if (rc) {
+		errno = rc;
 		perror("pthread_create");
 		exit(1);
 	}