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: Peter 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: Ingo Molnar <mingo@elte.hu>
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 65301c5..9b7c6d8 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -402,7 +402,7 @@
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 @@
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 @@
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) {
@@ -476,19 +483,65 @@
atexit(atexit_header);
- if (!system_wide) {
- pid = target_pid;
- if (pid == -1)
- pid = getpid();
-
- open_counters(profile_cpu, pid);
- } else {
- if (profile_cpu != -1) {
- open_counters(profile_cpu, target_pid);
- } else {
- for (i = 0; i < nr_cpus; i++)
- open_counters(i, target_pid);
+ if (target_pid == -1) {
+ pid = fork();
+ if (pid < 0) {
+ perror("failed to fork");
+ exit(-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) {
@@ -503,31 +556,6 @@
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 @@
}
}
+ /*
+ * Let the child rip
+ */
+ close(go_pipe[1]);
+
for (;;) {
int hits = samples;
@@ -634,7 +667,7 @@
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();