selftests/bpf: Reset process and thread affinity after each test/sub-test

Some tests and sub-tests are setting "custom" thread/process affinity and
don't reset it back. Instead of requiring each test to undo all this, ensure
that thread affinity is restored by test_progs test runner itself.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200314013932.4035712-3-andriin@fb.com

tools/testing/selftests/bpf/test_progs.c

 // SPDX-License-Identifier: GPL-2.0-only
 /* Copyright (c) 2017 Facebook
  */
+#define _GNU_SOURCE
 #include "test_progs.h"
 #include "cgroup_helpers.h"
 #include "bpf_rlimit.h"
 #include <argp.h>
-#include <string.h>
+#include <pthread.h>
+#include <sched.h>
 #include <signal.h>
+#include <string.h>
 #include <execinfo.h> /* backtrace */
 
 /* defined in test_progs.h */
@@ -90,6 +93,34 @@ static void skip_account(void)
 	}
 }
 
+static void stdio_restore(void);
+
+/* A bunch of tests set custom affinity per-thread and/or per-process. Reset
+ * it after each test/sub-test.
+ */
+static void reset_affinity() {
+
+	cpu_set_t cpuset;
+	int i, err;
+
+	CPU_ZERO(&cpuset);
+	for (i = 0; i < env.nr_cpus; i++)
+		CPU_SET(i, &cpuset);
+
+	err = sched_setaffinity(0, sizeof(cpuset), &cpuset);
+	if (err < 0) {
+		stdio_restore();
+		fprintf(stderr, "Failed to reset process affinity: %d!\n", err);
+		exit(-1);
+	}
+	err = pthread_setaffinity_np(pthread_self(), sizeof(cpuset), &cpuset);
+	if (err < 0) {
+		stdio_restore();
+		fprintf(stderr, "Failed to reset thread affinity: %d!\n", err);
+		exit(-1);
+	}
+}
+
 void test__end_subtest()
 {
 	struct prog_test_def *test = env.test;
@@ -107,6 +138,8 @@ void test__end_subtest()
 	       test->test_num, test->subtest_num,
 	       test->subtest_name, sub_error_cnt ? "FAIL" : "OK");
 
+	reset_affinity();
+
 	free(test->subtest_name);
 	test->subtest_name = NULL;
 }
@@ -679,6 +712,12 @@ int main(int argc, char **argv)
 	srand(time(NULL));
 
 	env.jit_enabled = is_jit_enabled();
+	env.nr_cpus = libbpf_num_possible_cpus();
+	if (env.nr_cpus < 0) {
+		fprintf(stderr, "Failed to get number of CPUs: %d!\n",
+			env.nr_cpus);
+		return -1;
+	}
 
 	stdio_hijack();
 	for (i = 0; i < prog_test_cnt; i++) {
@@ -709,6 +748,7 @@ int main(int argc, char **argv)
 			test->test_num, test->test_name,
 			test->error_cnt ? "FAIL" : "OK");
 
+		reset_affinity();
 		if (test->need_cgroup_cleanup)
 			cleanup_cgroup_environment();
 	}

tools/testing/selftests/bpf/test_progs.h

@@ -71,6 +71,7 @@ struct test_env {
 	FILE *stderr;
 	char *log_buf;
 	size_t log_cnt;
+	int nr_cpus;
 
 	int succ_cnt; /* successful tests */
 	int sub_succ_cnt; /* successful sub-tests */