1 files changed, 50 insertions, 14 deletions

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index c5a290727a92..201ef2367dcb 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -99,7 +99,7 @@ static u64			runtime_cycles_noise;
 #define ERR_PERF_OPEN \
 "Error: counter %d, sys_perf_counter_open() syscall returned with %d (%s)\n"
 
-static void create_perf_stat_counter(int counter)
+static void create_perf_stat_counter(int counter, int pid)
 {
         struct perf_counter_attr *attr = attrs + counter;
 
@@ -119,7 +119,7 @@ static void create_perf_stat_counter(int counter)
                 attr->inherit   = inherit;
                 attr->disabled  = 1;
 
-                fd[0][counter] = sys_perf_counter_open(attr, 0, -1, -1, 0);
+                fd[0][counter] = sys_perf_counter_open(attr, pid, -1, -1, 0);
                 if (fd[0][counter] < 0 && verbose)
                         fprintf(stderr, ERR_PERF_OPEN, counter,
                                 fd[0][counter], strerror(errno));
@@ -205,12 +205,58 @@ static int run_perf_stat(int argc, const char **argv)
         int status = 0;
         int counter;
         int pid;
+        int child_ready_pipe[2], go_pipe[2];
+        char buf;
 
         if (!system_wide)
                 nr_cpus = 1;
 
+        if (pipe(child_ready_pipe) < 0 || pipe(go_pipe) < 0) {
+                perror("failed to create pipes");
+                exit(1);
+        }
+
+        if ((pid = fork()) < 0)
+                perror("failed to fork");
+
+        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.
+                 */
+                read(go_pipe[0], &buf, 1);
+
+                execvp(argv[0], (char **)argv);
+
+                perror(argv[0]);
+                exit(-1);
+        }
+
+        /*
+         * Wait for the child to be ready to exec.
+         */
+        close(child_ready_pipe[1]);
+        close(go_pipe[0]);
+        read(child_ready_pipe[0], &buf, 1);
+        close(child_ready_pipe[0]);
+
         for (counter = 0; counter < nr_counters; counter++)
-                create_perf_stat_counter(counter);
+                create_perf_stat_counter(counter, pid);
 
         /*
          * Enable counters and exec the command:
@@ -218,19 +264,9 @@ static int run_perf_stat(int argc, const char **argv)
         t0 = rdclock();
         prctl(PR_TASK_PERF_COUNTERS_ENABLE);
 
-        if ((pid = fork()) < 0)
-                perror("failed to fork");
-
-        if (!pid) {
-                if (execvp(argv[0], (char **)argv)) {
-                        perror(argv[0]);
-                        exit(-1);
-                }
-        }
-
+        close(go_pipe[1]);
         wait(&status);
 
-        prctl(PR_TASK_PERF_COUNTERS_DISABLE);
         t1 = rdclock();
 
         walltime_nsecs[run_idx] = t1 - t0;