tracing: Add infrastructure to allow set_event_pid to follow children

Add the infrastructure needed to have the PIDs in set_event_pid to
automatically add PIDs of the children of the tasks that have their PIDs in
set_event_pid. This will also remove PIDs from set_event_pid when a task
exits

This is implemented by adding hooks into the fork and exit tracepoints. On
fork, the PIDs are added to the list, and on exit, they are removed.

Add a new option called event_fork that when set, PIDs in set_event_pid will
automatically get their children PIDs added when they fork, as well as any
task that exits will have its PID removed from set_event_pid.

This works for instances as well.

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

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a2f0b9f..0d12dbd 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3571,6 +3571,9 @@ int set_tracer_flag(struct trace_array *tr, unsigned int mask, int enabled)
        if (mask == TRACE_ITER_RECORD_CMD)
                trace_event_enable_cmd_record(enabled);
 
+       if (mask == TRACE_ITER_EVENT_FORK)
+               trace_event_follow_fork(tr, enabled);
+
        if (mask == TRACE_ITER_OVERWRITE) {
                ring_buffer_change_overwrite(tr->trace_buffer.buffer, enabled);
 #ifdef CONFIG_TRACER_MAX_TRACE

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 68cbb8e..2525042 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -655,6 +655,7 @@ static inline void __trace_stack(struct trace_array *tr, unsigned long flags,
 extern cycle_t ftrace_now(int cpu);
 
 extern void trace_find_cmdline(int pid, char comm[]);
+extern void trace_event_follow_fork(struct trace_array *tr, bool enable);
 
 #ifdef CONFIG_DYNAMIC_FTRACE
 extern unsigned long ftrace_update_tot_cnt;
@@ -966,6 +967,7 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
                C(STOP_ON_FREE,         "disable_on_free"),     \
                C(IRQ_INFO,             "irq-info"),            \
                C(MARKERS,              "markers"),             \
+               C(EVENT_FORK,           "event-fork"),          \
                FUNCTION_FLAGS                                  \
                FGRAPH_FLAGS                                    \
                STACK_FLAGS                                     \

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 45f7cc7..add81df 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -474,11 +474,23 @@ static void ftrace_clear_events(struct trace_array *tr)
 /* Shouldn't this be in a header? */
 extern int pid_max;
 
+/* Returns true if found in filter */
 static bool
-ignore_this_task(struct trace_pid_list *filtered_pids, struct task_struct *task)
+find_filtered_pid(struct trace_pid_list *filtered_pids, pid_t search_pid)
 {
-       pid_t pid;
+       /*
+        * If pid_max changed after filtered_pids was created, we
+        * by default ignore all pids greater than the previous pid_max.
+        */
+       if (search_pid >= filtered_pids->pid_max)
+               return false;
+
+       return test_bit(search_pid, filtered_pids->pids);
+}
 
+static bool
+ignore_this_task(struct trace_pid_list *filtered_pids, struct task_struct *task)
+{
        /*
         * Return false, because if filtered_pids does not exist,
         * all pids are good to trace.
@@ -486,16 +498,68 @@ ignore_this_task(struct trace_pid_list *filtered_pids, struct task_struct *task)
        if (!filtered_pids)
                return false;
 
-       pid = task->pid;
+       return !find_filtered_pid(filtered_pids, task->pid);
+}
 
-       /*
-        * If pid_max changed after filtered_pids was created, we
-        * by default ignore all pids greater than the previous pid_max.
-        */
-       if (task->pid >= filtered_pids->pid_max)
-               return true;
+static void filter_add_remove_task(struct trace_pid_list *pid_list,
+                                  struct task_struct *self,
+                                  struct task_struct *task)
+{
+       if (!pid_list)
+               return;
+
+       /* For forks, we only add if the forking task is listed */
+       if (self) {
+               if (!find_filtered_pid(pid_list, self->pid))
+                       return;
+       }
+
+       /* Sorry, but we don't support pid_max changing after setting */
+       if (task->pid >= pid_list->pid_max)
+               return;
+
+       /* "self" is set for forks, and NULL for exits */
+       if (self)
+               set_bit(task->pid, pid_list->pids);
+       else
+               clear_bit(task->pid, pid_list->pids);
+}
+
+static void
+event_filter_pid_sched_process_exit(void *data, struct task_struct *task)
+{
+       struct trace_pid_list *pid_list;
+       struct trace_array *tr = data;
+
+       pid_list = rcu_dereference_sched(tr->filtered_pids);
+       filter_add_remove_task(pid_list, NULL, task);
+}
 
-       return !test_bit(task->pid, filtered_pids->pids);
+static void
+event_filter_pid_sched_process_fork(void *data,
+                                   struct task_struct *self,
+                                   struct task_struct *task)
+{
+       struct trace_pid_list *pid_list;
+       struct trace_array *tr = data;
+
+       pid_list = rcu_dereference_sched(tr->filtered_pids);
+       filter_add_remove_task(pid_list, self, task);
+}
+
+void trace_event_follow_fork(struct trace_array *tr, bool enable)
+{
+       if (enable) {
+               register_trace_prio_sched_process_fork(event_filter_pid_sched_process_fork,
+                                                      tr, INT_MIN);
+               register_trace_prio_sched_process_exit(event_filter_pid_sched_process_exit,
+                                                      tr, INT_MAX);
+       } else {
+               unregister_trace_sched_process_fork(event_filter_pid_sched_process_fork,
+                                                   tr);
+               unregister_trace_sched_process_exit(event_filter_pid_sched_process_exit,
+                                                   tr);
+       }
 }
 
 static void