perf test: Add -F/--dont-fork option

Adding -F/--dont-fork option to bypass forking for each test. It's
useful for debugging test.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Tested-by: Nilay Vaish <nilayvaish@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1467113345-12669-1-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-test.txt

@@ -30,3 +30,7 @@ OPTIONS
 -v::
 --verbose::
 	Be more verbose.
+
+-F::
+--dont-fork::
+	Do not fork child for each test, run all tests within single process.

tools/perf/tests/builtin-test.c

@@ -14,6 +14,8 @@
 #include <subcmd/parse-options.h>
 #include "symbol.h"
 
+static bool dont_fork;
+
 struct test __weak arch_tests[] = {
 	{
 		.func = NULL,
@@ -247,7 +249,7 @@ static bool perf_test__matches(struct test *test, int curr, int argc, const char
 
 static int run_test(struct test *test, int subtest)
 {
-	int status, err = -1, child = fork();
+	int status, err = -1, child = dont_fork ? 0 : fork();
 	char sbuf[STRERR_BUFSIZE];
 
 	if (child < 0) {
@@ -257,9 +259,12 @@ static int run_test(struct test *test, int subtest)
 	}
 
 	if (!child) {
+		if (!dont_fork) {
 			pr_debug("test child forked, pid %d\n", getpid());
+
 			if (!verbose) {
 				int nullfd = open("/dev/null", O_WRONLY);
+
 				if (nullfd >= 0) {
 					close(STDERR_FILENO);
 					close(STDOUT_FILENO);
@@ -272,11 +277,14 @@ static int run_test(struct test *test, int subtest)
 				signal(SIGSEGV, sighandler_dump_stack);
 				signal(SIGFPE, sighandler_dump_stack);
 			}
+		}
 
 		err = test->func(subtest);
+		if (!dont_fork)
 			exit(err);
 	}
 
+	if (!dont_fork) {
 		wait(&status);
 
 		if (WIFEXITED(status)) {
@@ -286,6 +294,7 @@ static int run_test(struct test *test, int subtest)
 			err = -1;
 			pr_debug("test child interrupted\n");
 		}
+	}
 
 	return err;
 }
@@ -425,6 +434,8 @@ int cmd_test(int argc, const char **argv, const char *prefix __maybe_unused)
 	OPT_STRING('s', "skip", &skip, "tests", "tests to skip"),
 	OPT_INCR('v', "verbose", &verbose,
 		    "be more verbose (show symbol address, etc)"),
+	OPT_BOOLEAN('F', "dont-fork", &dont_fork,
+		    "Do not fork for testcase"),
 	OPT_END()
 	};
 	const char * const test_subcommands[] = { "list", NULL };