Commit c37775d5 authored by Steven Rostedt's avatar Steven Rostedt
Browse files

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: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f4d34a87

kernel/trace/trace.c

+3 −0
Original line number Diff line number Diff line
@@ -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

kernel/trace/trace.h

+2 −0
Original line number Diff line number Diff line
@@ -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					\

kernel/trace/trace_events.c

+74 −10
Original line number Diff line number Diff line
@@ -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;



	return !test_bit(task->pid, filtered_pids->pids);

	/* "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

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