Fix: add missing synchronization point for before app test case

Fixes a race where the application could generate all its events before
trace start.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/tests/utils/testapp/gen-ust-events/gen-ust-events.c b/tests/utils/testapp/gen-ust-events/gen-ust-events.c
index 42fa082a9faf30227cfb1f2610ce148eae776729..8d611ad5515ab68c2eb6b750bb65735ec5697c12 100644 (file)
--- a/tests/utils/testapp/gen-ust-events/gen-ust-events.c
+++ b/tests/utils/testapp/gen-ust-events/gen-ust-events.c
@@ -27,15 +27,21 @@
 #include <sys/types.h>
 #include <unistd.h>
 #include <stdbool.h>
+#include <signal.h>
+#include <poll.h>
+#include <errno.h>
 
 #define TRACEPOINT_DEFINE
 #include "tp.h"
 
 void create_file(const char *path)
 {
+       static bool file_created = false;
        int ret;
 
-       assert(path);
+       if (!path || file_created) {
+               return;
+       }
 
        ret = creat(path, S_IRWXU);
        if (ret < 0) {
@@ -44,6 +50,30 @@ void create_file(const char *path)
        }
 
        (void) close(ret);
+       file_created = true;
+}
+
+static
+void wait_on_file(const char *path)
+{
+       if (!path) {
+               return;
+       }
+       for (;;) {
+               int ret;
+               struct stat buf;
+
+               ret = stat(path, &buf);
+               if (ret == -1 && errno == ENOENT) {
+                       (void) poll(NULL, 0, 10);       /* 10 ms delay */
+                       continue;                       /* retry */
+               }
+               if (ret) {
+                       perror("stat");
+                       exit(EXIT_FAILURE);
+               }
+               break;  /* found */
+       }
 }
 
 int main(int argc, char **argv)
@@ -55,8 +85,8 @@ int main(int argc, char **argv)
        float flt = 2222.0;
        int nr_iter = 100;
        useconds_t nr_usec = 0;
-       char *tmp_file_path = NULL;
-       bool file_created = false;
+       char *after_first_event_file_path = NULL;
+       char *before_last_event_file_path = NULL;
 
        if (argc >= 2) {
                /*
@@ -71,22 +101,30 @@ int main(int argc, char **argv)
        }
 
        if (argc >= 4) {
-               tmp_file_path = argv[3];
+               after_first_event_file_path = argv[3];
+       }
+
+       if (argc >= 5) {
+               before_last_event_file_path = argv[4];
        }
 
        for (i = 0; nr_iter < 0 || i < nr_iter; i++) {
+               if (nr_iter >= 0 && i == nr_iter - 1) {
+                       /*
+                        * Wait on synchronization before writing last
+                        * event.
+                        */
+                       wait_on_file(before_last_event_file_path);
+               }
                netint = htonl(i);
-               tracepoint(tp, tptest, i, netint, values, text, strlen(text), dbl,
-                               flt);
+               tracepoint(tp, tptest, i, netint, values, text,
+                       strlen(text), dbl, flt);
 
                /*
-                * First loop we create the file if asked to indicate that at least one
-                * tracepoint has been hit.
+                * First loop we create the file if asked to indicate
+                * that at least one tracepoint has been hit.
                 */
-               if (!file_created && tmp_file_path) {
-                       create_file(tmp_file_path);
-                       file_created = true;
-               }
+               create_file(after_first_event_file_path);
                usleep(nr_usec);
        }