perf record: We should fork only if a program was specified to run

IOW: Now 'perf record -a' works, this was a bug introduced in:

856e96608a72412d319e498a3a7c557571f811bd
"perf record: Properly synchronize child creation"

Also fix the -C usage, i.e. allow for profiling all the tasks in
one CPU.

Reported-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1261957026-15580-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 8 insertions, 6 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 63136d0534d4..265425322734 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -402,7 +402,7 @@ static void atexit_header(void)
         perf_header__write(&session->header, output, true);
 }
 
-static int __cmd_record(int argc __used, const char **argv)
+static int __cmd_record(int argc, const char **argv)
 {
         int i, counter;
         struct stat st;
@@ -411,6 +411,7 @@ static int __cmd_record(int argc __used, const char **argv)
         int err;
         unsigned long waking = 0;
         int child_ready_pipe[2], go_pipe[2];
+        const bool forks = target_pid == -1 && argc > 0;
         char buf;
 
         page_size = sysconf(_SC_PAGE_SIZE);
@@ -422,7 +423,7 @@ static int __cmd_record(int argc __used, const char **argv)
         signal(SIGCHLD, sig_handler);
         signal(SIGINT, sig_handler);
 
-        if (pipe(child_ready_pipe) < 0 || pipe(go_pipe) < 0) {
+        if (forks && (pipe(child_ready_pipe) < 0 || pipe(go_pipe) < 0)) {
                 perror("failed to create pipes");
                 exit(-1);
         }
@@ -483,7 +484,7 @@ static int __cmd_record(int argc __used, const char **argv)
 
         atexit(atexit_header);
 
-        if (target_pid == -1) {
+        if (forks) {
                 pid = fork();
                 if (pid < 0) {
                         perror("failed to fork");
@@ -550,7 +551,7 @@ static int __cmd_record(int argc __used, const char **argv)
                         return err;
         }
 
-        if (!system_wide)
+        if (!system_wide && profile_cpu == -1)
                 event__synthesize_thread(pid, process_synthesized_event,
                                          session);
         else
@@ -569,7 +570,8 @@ static int __cmd_record(int argc __used, const char **argv)
         /*
          * Let the child rip
          */
-        close(go_pipe[1]);
+        if (forks)
+                close(go_pipe[1]);
 
         for (;;) {
                 int hits = samples;
@@ -667,7 +669,7 @@ 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 || profile_cpu == -1))
+        if (!argc && target_pid == -1 && !system_wide && profile_cpu == -1)
                 usage_with_options(record_usage, options);
 
         symbol__init();