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Commit 75b8e982 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt
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tracing/filter: Swap entire filter of events 



When creating a new filter, instead of allocating the filter to the
event call first and then processing the filter, it is easier to
process a temporary filter and then just swap it with the call filter.
By doing this, it simplifies the code.

A filter is allocated and processed, when it is done, it is
swapped with the call filter, synchronize_sched() is called to make
sure all callers are done with the old filter (filters are called
with premption disabled), and then the old filter is freed.

Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent bf93f9ed

kernel/trace/trace_events_filter.c

+146 −105
Original line number Diff line number Diff line
@@ -425,10 +425,15 @@ int filter_match_preds(struct event_filter *filter, void *rec) 
	struct filter_pred *preds;

	struct filter_pred *pred;

	struct filter_pred *root;

	int n_preds = ACCESS_ONCE(filter->n_preds);

	int n_preds;

	int done = 0;



	/* no filter is considered a match */

	if (!filter)

		return 1;



	n_preds = filter->n_preds;



	if (!n_preds)

		return 1;
@@ -509,6 +514,9 @@ static void parse_error(struct filter_parse_state *ps, int err, int pos) 


static void remove_filter_string(struct event_filter *filter)

{

	if (!filter)

		return;



	kfree(filter->filter_string);

	filter->filter_string = NULL;

}
@@ -568,9 +576,10 @@ static void append_filter_err(struct filter_parse_state *ps, 


void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s)

{

	struct event_filter *filter = call->filter;

	struct event_filter *filter;



	mutex_lock(&event_mutex);

	filter = call->filter;

	if (filter && filter->filter_string)

		trace_seq_printf(s, "%s\n", filter->filter_string);

	else
@@ -581,9 +590,10 @@ void print_event_filter(struct ftrace_event_call *call, struct trace_seq *s) 
void print_subsystem_event_filter(struct event_subsystem *system,

				  struct trace_seq *s)

{

	struct event_filter *filter = system->filter;

	struct event_filter *filter;



	mutex_lock(&event_mutex);

	filter = system->filter;

	if (filter && filter->filter_string)

		trace_seq_printf(s, "%s\n", filter->filter_string);

	else
@@ -745,26 +755,9 @@ static void __free_preds(struct event_filter *filter) 
	filter->n_preds = 0;

}



static void reset_preds(struct event_filter *filter)

static void filter_disable(struct ftrace_event_call *call)

{

	int n_preds = filter->n_preds;

	int i;



	filter->n_preds = 0;

	filter->root = NULL;

	if (!filter->preds)

		return;



	for (i = 0; i < n_preds; i++)

		filter->preds[i].fn = filter_pred_none;

}



static void filter_disable_preds(struct ftrace_event_call *call)

{

	struct event_filter *filter = call->filter;



	call->flags &= ~TRACE_EVENT_FL_FILTERED;

	reset_preds(filter);

}



static void __free_filter(struct event_filter *filter)
@@ -777,11 +770,16 @@ static void __free_filter(struct event_filter *filter) 
	kfree(filter);

}



/*

 * Called when destroying the ftrace_event_call.

 * The call is being freed, so we do not need to worry about

 * the call being currently used. This is for module code removing

 * the tracepoints from within it.

 */

void destroy_preds(struct ftrace_event_call *call)

{

	__free_filter(call->filter);

	call->filter = NULL;

	call->flags &= ~TRACE_EVENT_FL_FILTERED;

}



static struct event_filter *__alloc_filter(void)
@@ -789,11 +787,6 @@ static struct event_filter *__alloc_filter(void) 
	struct event_filter *filter;



	filter = kzalloc(sizeof(*filter), GFP_KERNEL);

	if (!filter)

		return ERR_PTR(-ENOMEM);



	filter->n_preds = 0;



	return filter;

}
@@ -838,46 +831,28 @@ static int __alloc_preds(struct event_filter *filter, int n_preds) 
	return 0;

}



static int init_filter(struct ftrace_event_call *call)

{

	if (call->filter)

		return 0;



	call->flags &= ~TRACE_EVENT_FL_FILTERED;

	call->filter = __alloc_filter();

	if (IS_ERR(call->filter))

		return PTR_ERR(call->filter);



	return 0;

}



static int init_subsystem_preds(struct event_subsystem *system)

static void filter_free_subsystem_preds(struct event_subsystem *system)

{

	struct ftrace_event_call *call;

	int err;



	list_for_each_entry(call, &ftrace_events, list) {

		if (strcmp(call->class->system, system->name) != 0)

			continue;



		err = init_filter(call);

		if (err)

			return err;

		filter_disable(call);

		remove_filter_string(call->filter);

	}



	return 0;

}



static void filter_free_subsystem_preds(struct event_subsystem *system)

static void filter_free_subsystem_filters(struct event_subsystem *system)

{

	struct ftrace_event_call *call;



	list_for_each_entry(call, &ftrace_events, list) {

		if (strcmp(call->class->system, system->name) != 0)

			continue;



		filter_disable_preds(call);

		remove_filter_string(call->filter);

		__free_filter(call->filter);

		call->filter = NULL;

	}

}
@@ -1743,88 +1718,129 @@ static int replace_preds(struct ftrace_event_call *call, 
	return err;

}



struct filter_list {

	struct list_head	list;

	struct event_filter	*filter;

};



static int replace_system_preds(struct event_subsystem *system,

				struct filter_parse_state *ps,

				char *filter_string)

{

	struct ftrace_event_call *call;

	struct filter_list *filter_item;

	struct filter_list *tmp;

	LIST_HEAD(filter_list);

	bool fail = true;

	int err;



	list_for_each_entry(call, &ftrace_events, list) {

		struct event_filter *filter = call->filter;



		if (strcmp(call->class->system, system->name) != 0)

			continue;



		/* try to see if the filter can be applied */

		err = replace_preds(call, filter, ps, filter_string, true);

		/*

		 * Try to see if the filter can be applied

		 *  (filter arg is ignored on dry_run)

		 */

		err = replace_preds(call, NULL, ps, filter_string, true);

		if (err)

			goto fail;

	}



	/* set all filter pred counts to zero */

	list_for_each_entry(call, &ftrace_events, list) {

		struct event_filter *filter = call->filter;

		struct event_filter *filter;



		if (strcmp(call->class->system, system->name) != 0)

			continue;



		reset_preds(filter);

	}

		filter_item = kzalloc(sizeof(*filter_item), GFP_KERNEL);

		if (!filter_item)

			goto fail_mem;



	/*

	 * Since some of the preds may be used under preemption

	 * we need to wait for them to finish before we may

	 * reallocate them.

	 */

	synchronize_sched();

		list_add_tail(&filter_item->list, &filter_list);



	list_for_each_entry(call, &ftrace_events, list) {

		struct event_filter *filter = call->filter;

		filter_item->filter = __alloc_filter();

		if (!filter_item->filter)

			goto fail_mem;

		filter = filter_item->filter;



		if (strcmp(call->class->system, system->name) != 0)

			continue;

		/* Can only fail on no memory */

		err = replace_filter_string(filter, filter_string);

		if (err)

			goto fail_mem;



		/* really apply the filter */

		filter_disable_preds(call);

		err = replace_preds(call, filter, ps, filter_string, false);

		if (err)

			filter_disable_preds(call);

		else {

		if (err) {

			filter_disable(call);

			parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);

			append_filter_err(ps, filter);

		} else

			call->flags |= TRACE_EVENT_FL_FILTERED;

			replace_filter_string(filter, filter_string);

		}

		/*

		 * Regardless of if this returned an error, we still

		 * replace the filter for the call.

		 */

		filter = call->filter;

		call->filter = filter_item->filter;

		filter_item->filter = filter;



		fail = false;

	}



	if (fail)

		goto fail;



	/*

	 * The calls can still be using the old filters.

	 * Do a synchronize_sched() to ensure all calls are

	 * done with them before we free them.

	 */

	synchronize_sched();

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

		__free_filter(filter_item->filter);

		list_del(&filter_item->list);

		kfree(filter_item);

	}

	return 0;

 fail:

	/* No call succeeded */

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

		list_del(&filter_item->list);

		kfree(filter_item);

	}

	parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);

	return -EINVAL;

 fail_mem:

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

	if (!fail)

		synchronize_sched();

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

		__free_filter(filter_item->filter);

		list_del(&filter_item->list);

		kfree(filter_item);

	}

	return -ENOMEM;

}



int apply_event_filter(struct ftrace_event_call *call, char *filter_string)

{

	int err;

	struct filter_parse_state *ps;

	struct event_filter *filter;

	struct event_filter *tmp;

	int err = 0;



	mutex_lock(&event_mutex);



	err = init_filter(call);

	if (err)

		goto out_unlock;



	if (!strcmp(strstrip(filter_string), "0")) {

		filter_disable_preds(call);

		reset_preds(call->filter);

		filter_disable(call);

		filter = call->filter;

		if (!filter)

			goto out_unlock;

		call->filter = NULL;

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

		synchronize_sched();

		__free_preds(call->filter);

		remove_filter_string(call->filter);

		__free_filter(filter);

		goto out_unlock;

	}
@@ -1833,29 +1849,41 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string) 
	if (!ps)

		goto out_unlock;



	filter_disable_preds(call);

	replace_filter_string(call->filter, filter_string);

	filter = __alloc_filter();

	if (!filter) {

		kfree(ps);

		goto out_unlock;

	}



	replace_filter_string(filter, filter_string);



	parse_init(ps, filter_ops, filter_string);

	err = filter_parse(ps);

	if (err) {

		append_filter_err(ps, call->filter);

		append_filter_err(ps, filter);

		goto out;

	}



	err = replace_preds(call, filter, ps, filter_string, false);

	if (err) {

		filter_disable(call);

		append_filter_err(ps, filter);

	} else

		call->flags |= TRACE_EVENT_FL_FILTERED;

out:

	/*

	 * Make sure all the pred counts are zero so that

	 * no task is using it when we reallocate the preds array.

	 * Always swap the call filter with the new filter

	 * even if there was an error. If there was an error

	 * in the filter, we disable the filter and show the error

	 * string

	 */

	reset_preds(call->filter);

	tmp = call->filter;

	call->filter = filter;

	if (tmp) {

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

		synchronize_sched();



	err = replace_preds(call, call->filter, ps, filter_string, false);

	if (err)

		append_filter_err(ps, call->filter);

	else

		call->flags |= TRACE_EVENT_FL_FILTERED;

out:

		__free_filter(tmp);

	}

	filter_opstack_clear(ps);

	postfix_clear(ps);

	kfree(ps);
@@ -1868,18 +1896,21 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string) 
int apply_subsystem_event_filter(struct event_subsystem *system,

				 char *filter_string)

{

	int err;

	struct filter_parse_state *ps;

	struct event_filter *filter;

	int err = 0;



	mutex_lock(&event_mutex);



	err = init_subsystem_preds(system);

	if (err)

		goto out_unlock;



	if (!strcmp(strstrip(filter_string), "0")) {

		filter_free_subsystem_preds(system);

		remove_filter_string(system->filter);

		filter = system->filter;

		system->filter = NULL;

		/* Ensure all filters are no longer used */

		synchronize_sched();

		filter_free_subsystem_filters(system);

		__free_filter(filter);

		goto out_unlock;

	}
@@ -1888,7 +1919,17 @@ int apply_subsystem_event_filter(struct event_subsystem *system, 
	if (!ps)

		goto out_unlock;



	replace_filter_string(system->filter, filter_string);

	filter = __alloc_filter();

	if (!filter)

		goto out;



	replace_filter_string(filter, filter_string);

	/*

	 * No event actually uses the system filter

	 * we can free it without synchronize_sched().

	 */

	__free_filter(system->filter);

	system->filter = filter;



	parse_init(ps, filter_ops, filter_string);

	err = filter_parse(ps);
@@ -1945,7 +1986,7 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id, 
		goto out_unlock;



	filter = __alloc_filter();

	if (IS_ERR(filter)) {

	if (!filter) {

		err = PTR_ERR(filter);

		goto out_unlock;

	}