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Commit e0a568dc authored by Steven Rostedt (VMware)'s avatar Steven Rostedt (VMware)
Browse files

tracing: Fix synchronizing to event changes with tracepoint_synchronize_unregister() 



Now that some trace events can be protected by srcu_read_lock(tracepoint_srcu),
we need to make sure all locations that depend on this are also protected.
There were many places that did a synchronize_sched() thinking that it was
enough to protect againts access to trace events. This use to be the case,
but now that we use SRCU for _rcuidle() trace events, they may not be
protected by synchronize_sched(), as they may be called in paths that RCU is
not watching for preempt disable.

Fixes: e6753f23 ("tracepoint: Make rcuidle tracepoint callers use SRCU")
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent b207de3e

kernel/trace/trace_events.c

+4 −4
Original line number Diff line number Diff line
@@ -636,7 +636,7 @@ static void __ftrace_clear_event_pids(struct trace_array *tr) 
	rcu_assign_pointer(tr->filtered_pids, NULL);



	/* Wait till all users are no longer using pid filtering */

	synchronize_sched();

	tracepoint_synchronize_unregister();



	trace_free_pid_list(pid_list);

}
@@ -1622,7 +1622,7 @@ ftrace_event_pid_write(struct file *filp, const char __user *ubuf, 
	}



	if (filtered_pids) {

		synchronize_sched();

		tracepoint_synchronize_unregister();

		trace_free_pid_list(filtered_pids);

	} else if (pid_list) {

		/*
@@ -3036,8 +3036,8 @@ int event_trace_del_tracer(struct trace_array *tr) 
	/* Disable any running events */

	__ftrace_set_clr_event_nolock(tr, NULL, NULL, NULL, 0);



	/* Access to events are within rcu_read_lock_sched() */

	synchronize_sched();

	/* Make sure no more events are being executed */

	tracepoint_synchronize_unregister();



	down_write(&trace_event_sem);

	__trace_remove_event_dirs(tr);

kernel/trace/trace_events_filter.c

+8 −7
Original line number Diff line number Diff line
@@ -899,7 +899,8 @@ int filter_match_preds(struct event_filter *filter, void *rec) 
	if (!filter)

		return 1;



	prog = rcu_dereference_sched(filter->prog);

	/* Protected by either SRCU(tracepoint_srcu) or preempt_disable */

	prog = rcu_dereference_raw(filter->prog);

	if (!prog)

		return 1;
@@ -1626,10 +1627,10 @@ static int process_system_preds(struct trace_subsystem_dir *dir, 


	/*

	 * The calls can still be using the old filters.

	 * Do a synchronize_sched() to ensure all calls are

	 * Do a synchronize_sched() and to ensure all calls are

	 * done with them before we free them.

	 */

	synchronize_sched();

	tracepoint_synchronize_unregister();

	list_for_each_entry_safe(filter_item, tmp, &filter_list, list) {

		__free_filter(filter_item->filter);

		list_del(&filter_item->list);
@@ -1648,7 +1649,7 @@ static int process_system_preds(struct trace_subsystem_dir *dir, 
	kfree(filter);

	/* If any call succeeded, we still need to sync */

	if (!fail)

		synchronize_sched();

		tracepoint_synchronize_unregister();

	list_for_each_entry_safe(filter_item, tmp, &filter_list, list) {

		__free_filter(filter_item->filter);

		list_del(&filter_item->list);
@@ -1790,7 +1791,7 @@ int apply_event_filter(struct trace_event_file *file, char *filter_string) 
		event_clear_filter(file);



		/* Make sure the filter is not being used */

		synchronize_sched();

		tracepoint_synchronize_unregister();

		__free_filter(filter);



		return 0;
@@ -1817,7 +1818,7 @@ int apply_event_filter(struct trace_event_file *file, char *filter_string) 


		if (tmp) {

			/* Make sure the call is done with the filter */

			synchronize_sched();

			tracepoint_synchronize_unregister();

			__free_filter(tmp);

		}

	}
@@ -1847,7 +1848,7 @@ int apply_subsystem_event_filter(struct trace_subsystem_dir *dir, 
		filter = system->filter;

		system->filter = NULL;

		/* Ensure all filters are no longer used */

		synchronize_sched();

		tracepoint_synchronize_unregister();

		filter_free_subsystem_filters(dir, tr);

		__free_filter(filter);

		goto out_unlock;

kernel/trace/trace_events_hist.c

+1 −1
Original line number Diff line number Diff line
@@ -5141,7 +5141,7 @@ static void hist_clear(struct event_trigger_data *data) 
	if (data->name)

		pause_named_trigger(data);



	synchronize_sched();

	tracepoint_synchronize_unregister();



	tracing_map_clear(hist_data->map);

kernel/trace/trace_events_trigger.c

+4 −2
Original line number Diff line number Diff line
@@ -34,7 +34,9 @@ void trigger_data_free(struct event_trigger_data *data) 
	if (data->cmd_ops->set_filter)

		data->cmd_ops->set_filter(NULL, data, NULL);



	synchronize_sched(); /* make sure current triggers exit before free */

	/* make sure current triggers exit before free */

	tracepoint_synchronize_unregister();



	kfree(data);

}
@@ -752,7 +754,7 @@ int set_trigger_filter(char *filter_str, 


	if (tmp) {

		/* Make sure the call is done with the filter */

		synchronize_sched();

		tracepoint_synchronize_unregister();

		free_event_filter(tmp);

	}