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Commit 856e9660 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf record: Properly synchronize child creation 



Remove that ugly usleep and provide proper serialization between
parent and child just like perf-stat does.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: fweisbec@gmail.com
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091216165904.908184135@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent f4c4176f

tools/perf/builtin-record.c

+71 −38
Original line number Diff line number Diff line
@@ -402,7 +402,7 @@ static void atexit_header(void) 
	perf_header__write(&session->header, output, true);

}



static int __cmd_record(int argc, const char **argv)

static int __cmd_record(int argc __used, const char **argv)

{

	int i, counter;

	struct stat st;
@@ -410,6 +410,8 @@ static int __cmd_record(int argc, const char **argv) 
	int flags;

	int err;

	unsigned long waking = 0;

	int child_ready_pipe[2], go_pipe[2];

	char buf;



	page_size = sysconf(_SC_PAGE_SIZE);

	nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
@@ -420,6 +422,11 @@ static int __cmd_record(int argc, const char **argv) 
	signal(SIGCHLD, sig_handler);

	signal(SIGINT, sig_handler);



	if (pipe(child_ready_pipe) < 0 || pipe(go_pipe) < 0) {

		perror("failed to create pipes");

		exit(-1);

	}



	if (!stat(output_name, &st) && st.st_size) {

		if (!force) {

			if (!append_file) {
@@ -476,20 +483,66 @@ static int __cmd_record(int argc, const char **argv) 


	atexit(atexit_header);



	if (!system_wide) {

		pid = target_pid;

		if (pid == -1)

			pid = getpid();

	if (target_pid == -1) {

		pid = fork();

		if (pid < 0) {

			perror("failed to fork");

			exit(-1);

		}



		open_counters(profile_cpu, pid);

	} else {

		if (profile_cpu != -1) {

		if (!pid) {

			close(child_ready_pipe[0]);

			close(go_pipe[1]);

			fcntl(go_pipe[0], F_SETFD, FD_CLOEXEC);



			/*

			 * Do a dummy execvp to get the PLT entry resolved,

			 * so we avoid the resolver overhead on the real

			 * execvp call.

			 */

			execvp("", (char **)argv);



			/*

			 * Tell the parent we're ready to go

			 */

			close(child_ready_pipe[1]);



			/*

			 * Wait until the parent tells us to go.

			 */

			if (read(go_pipe[0], &buf, 1) == -1)

				perror("unable to read pipe");



			execvp(argv[0], (char **)argv);



			perror(argv[0]);

			exit(-1);

		}



		child_pid = pid;



		if (!system_wide)

			target_pid = pid;



		close(child_ready_pipe[1]);

		close(go_pipe[0]);

		/*

		 * wait for child to settle

		 */

		if (read(child_ready_pipe[0], &buf, 1) == -1) {

			perror("unable to read pipe");

			exit(-1);

		}

		close(child_ready_pipe[0]);

	}





	if (!system_wide || profile_cpu != -1) {

		open_counters(profile_cpu, target_pid);

	} else {

		for (i = 0; i < nr_cpus; i++)

			open_counters(i, target_pid);

	}

	}



	if (file_new) {

		err = perf_header__write(&session->header, output, false);
@@ -503,31 +556,6 @@ static int __cmd_record(int argc, const char **argv) 
	else

		event__synthesize_threads(process_synthesized_event, session);



	if (target_pid == -1 && argc) {

		pid = fork();

		if (pid < 0)

			die("failed to fork");



		if (!pid) {

			if (execvp(argv[0], (char **)argv)) {

				perror(argv[0]);

				exit(-1);

			}

		} else {

			/*

			 * Wait a bit for the execv'ed child to appear

			 * and be updated in /proc

			 * FIXME: Do you know a less heuristical solution?

			 */

			usleep(1000);

			event__synthesize_thread(pid,

						 process_synthesized_event,

						 session);

		}



		child_pid = pid;

	}



	if (realtime_prio) {

		struct sched_param param;
@@ -538,6 +566,11 @@ static int __cmd_record(int argc, const char **argv) 
		}

	}



	/*

	 * Let the child rip

	 */

	close(go_pipe[1]);



	for (;;) {

		int hits = samples;
@@ -634,7 +667,7 @@ int cmd_record(int argc, const char **argv, const char *prefix __used) 


	argc = parse_options(argc, argv, options, record_usage,

			    PARSE_OPT_STOP_AT_NON_OPTION);

	if (!argc && target_pid == -1 && !system_wide)

	if (!argc && target_pid == -1 && (!system_wide || profile_cpu == -1))

		usage_with_options(record_usage, options);



	symbol__init();