trace-cmd: Add sched_switch to and wake up of pid to filter

If the -F option is set, include events that wake up that pid or
switch to it. That is, even if the event is done by another task,
if that task calls the wakeup event to the filtered pid, it should
also be shown, as well as the context switches to the filtered task.

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

1 files changed, 62 insertions, 2 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index 6c3d91c..4466f93 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -283,7 +283,7 @@ static void update_ftrace_pid(const char *pid)
         close(fd);
 }
 
-static void update_pid_event_filters(char *pid);
+static void update_pid_event_filters(const char *pid);
 static void enable_tracing(void);
 
 static void update_task_filter(void)
@@ -720,7 +720,60 @@ static void disable_all(void)
         clear_trace();
 }
 
-static void update_pid_event_filters(char *pid)
+static void update_filter(const char *event_name, const char *field,
+                          const char *pid)
+{
+        char buf[BUFSIZ];
+        char *filter_name;
+        char *path;
+        char *filter;
+        int fd;
+        int ret;
+
+        filter_name = malloc_or_die(strlen(event_name) +
+                                    strlen("events//filter") + 1);
+        sprintf(filter_name, "events/%s/filter", event_name);
+
+        path = get_tracing_file(filter_name);
+        free(filter_name);
+
+        /* Ignore if file does not exist */
+        fd = open(path, O_RDONLY);
+        if (fd < 0)
+                goto out;
+
+        ret = read(fd, buf, BUFSIZ);
+        if (ret < 0)
+                die("Can't read %s", path);
+        close(fd);
+
+        /* append unless there is currently no filter */
+        if (strcmp(buf, "none") == 0) {
+                filter = malloc_or_die(strlen(pid) + strlen(field) +
+                                       strlen("(==)") + 1);
+                sprintf(filter, "(%s==%s)", field, pid);
+        } else {
+                filter = malloc_or_die(strlen(pid) + strlen(field) +
+                                       strlen(buf) + strlen("()||(==)") + 1);
+                sprintf(filter, "(%s)||(%s==%s)", buf, field, pid);
+        }
+
+        fd = open(path, O_WRONLY);
+        if (fd < 0)
+                die("can't open %s", path);
+
+        ret = write(fd, filter, strlen(filter));
+        if (ret < 0)
+                die("Can't write to %s", path);
+        close(fd);
+
+        free(filter);
+
+ out:
+        put_tracing_file(path);
+}
+
+static void update_pid_event_filters(const char *pid)
 {
         struct event_list *event;
         char *filter;
@@ -745,6 +798,13 @@ static void update_pid_event_filters(char *pid)
         }
 
         free(filter);
+
+        /*
+         * Also make sure that the sched_switch to this pid
+         * and wakeups of this pid are also traced.
+         */
+        update_filter("sched/sched_switch", "next_pid", pid);
+        update_filter("sched/sched_wakeup", "pid", pid);
 }
 
 static void enable_events(void)