trace-cmd: Allow update_ftrace_pid() to allow multiple calls

Change the way update_ftrace_pid() to allow multiple calls
to add more than one pid.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 34 insertions, 12 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index 5055db6..e1341bf 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -317,19 +317,37 @@ static void reset_max_latency(void)
         fclose(fp);
 }
 
-static void update_ftrace_pid(const char *pid)
+static void update_ftrace_pid(const char *pid, int reset)
 {
-        char *path;
+        static char *path;
         int ret;
-        int fd;
+        static int fd = -1;
 
-        path = tracecmd_get_tracing_file("set_ftrace_pid");
-        if (!path)
+        if (!pid) {
+                if (fd >= 0)
+                        close(fd);
+                if (path)
+                        tracecmd_put_tracing_file(path);
+                fd = -1;
+                path = NULL;
                 return;
+        }
 
-        fd = open(path, O_WRONLY | O_TRUNC);
-        if (fd < 0)
-                return;
+        /* Force reopen on reset */
+        if (reset && fd >= 0) {
+                close(fd);
+                fd = -1;
+        }
+
+        if (fd < 0) {
+                if (!path)
+                        path = tracecmd_get_tracing_file("set_ftrace_pid");
+                if (!path)
+                        return;
+                fd = open(path, O_WRONLY | (reset ? O_TRUNC : 0));
+                if (fd < 0)
+                        return;
+        }
 
         ret = write(fd, pid, strlen(pid));
 
@@ -342,7 +360,8 @@ static void update_ftrace_pid(const char *pid)
         if (ret < 0)
                 die("error writing to %s", path);
 
-        close(fd);
+        /* add whitespace in case another pid is written */
+        write(fd, " ", 1);
 }
 
 static void update_pid_event_filters(const char *pid);
@@ -354,7 +373,7 @@ static void update_task_filter(void)
         char spid[100];
 
         if (!filter_task && filter_pid < 0) {
-                update_ftrace_pid("");
+                update_ftrace_pid("", 1);
                 enable_tracing();
                 return;
         }
@@ -364,7 +383,7 @@ static void update_task_filter(void)
 
         snprintf(spid, 100, "%d", pid);
 
-        update_ftrace_pid(spid);
+        update_ftrace_pid(spid, 1);
 
         update_pid_event_filters(spid);
 
@@ -837,7 +856,10 @@ static void disable_all(void)
 
         set_plugin("nop");
         update_event("all", "0", 0, '0');
-        update_ftrace_pid("");
+
+        /* Force close and reset of ftrace pid file */
+        update_ftrace_pid("", 1);
+        update_ftrace_pid(NULL, 0);
 
         clear_trace();
 }