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tracing: Add infrastructure to allow set_event_pid to follow children

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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>
This commit is contained in:
Steven Rostedt
2016-04-13 16:59:18 -04:00
parent f4d34a87e9
commit c37775d578
3 changed files with 79 additions and 10 deletions
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84
kernel/trace/trace_events.c
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@@ -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
find_filtered_pid(struct trace_pid_list *filtered_pids, pid_t search_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)
{
pid_t pid;
/*
* 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;
return !test_bit(task->pid, filtered_pids->pids);
/* 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);
}
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