perf tools: Fix --pid option for stat

current pid option doesn't work for perf stat. Change it to what
perf record --pid acts as.
Signed-off-by: Liming Wang <liming.wang@windriver.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1262246750-2191-1-git-send-email-liming.wang@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-stat.c

@@ -44,6 +44,7 @@
 #include "util/parse-events.h"
 #include "util/event.h"
 #include "util/debug.h"
+#include "util/header.h"
 
 #include <sys/prctl.h>
 #include <math.h>
@@ -79,6 +80,8 @@ static int			fd[MAX_NR_CPUS][MAX_COUNTERS];
 
 static int			event_scaled[MAX_COUNTERS];
 
+static volatile int done = 0;
+
 struct stats
 {
 	double n, mean, M2;
@@ -247,18 +250,20 @@ static int run_perf_stat(int argc __used, const char **argv)
 	unsigned long long t0, t1;
 	int status = 0;
 	int counter;
-	int pid;
+	int pid = target_pid;
 	int child_ready_pipe[2], go_pipe[2];
+	const bool forks = (target_pid == -1 && argc > 0);
 	char buf;
 
 	if (!system_wide)
 		nr_cpus = 1;
 
-	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);
 	}
 
+	if (forks) {
 		if ((pid = fork()) < 0)
 			perror("failed to fork");
 
@@ -301,6 +306,7 @@ static int run_perf_stat(int argc __used, const char **argv)
 		if (read(child_ready_pipe[0], &buf, 1) == -1)
 			perror("unable to read pipe");
 		close(child_ready_pipe[0]);
+	}
 
 	for (counter = 0; counter < nr_counters; counter++)
 		create_perf_stat_counter(counter, pid);
@@ -310,8 +316,12 @@ static int run_perf_stat(int argc __used, const char **argv)
 	 */
 	t0 = rdclock();
 
+	if (forks) {
 		close(go_pipe[1]);
 		wait(&status);
+	} else {
+		while(!done);
+	}
 
 	t1 = rdclock();
 
@@ -417,10 +427,13 @@ static void print_stat(int argc, const char **argv)
 	fflush(stdout);
 
 	fprintf(stderr, "\n");
-	fprintf(stderr, " Performance counter stats for \'%s", argv[0]);
-
+	fprintf(stderr, " Performance counter stats for ");
+	if(target_pid == -1) {
+		fprintf(stderr, "\'%s", argv[0]);
 		for (i = 1; i < argc; i++)
 			fprintf(stderr, " %s", argv[i]);
+	}else
+		fprintf(stderr, "task pid \'%d", target_pid);
 
 	fprintf(stderr, "\'");
 	if (run_count > 1)
@@ -445,6 +458,9 @@ static volatile int signr = -1;
 
 static void skip_signal(int signo)
 {
+	if(target_pid != -1)
+		done = 1;
+
 	signr = signo;
 }
 
@@ -461,7 +477,7 @@ static void sig_atexit(void)
 }
 
 static const char * const stat_usage[] = {
-	"perf stat [<options>] <command>",
+	"perf stat [<options>] [<command>]",
 	NULL
 };
 
@@ -492,7 +508,7 @@ int cmd_stat(int argc, const char **argv, const char *prefix __used)
 
 	argc = parse_options(argc, argv, options, stat_usage,
 		PARSE_OPT_STOP_AT_NON_OPTION);
-	if (!argc)
+	if (!argc && target_pid == -1)
 		usage_with_options(stat_usage, options);
 	if (run_count <= 0)
 		usage_with_options(stat_usage, options);