[RFC][PATCH 04/12] tracing/filter: Call synchronize_sched() just once for system filters

From: Steven Rostedt
Date: Thu Jan 27 2011 - 23:34:10 EST


From: Steven Rostedt <srostedt@xxxxxxxxxx>

By separating out the reseting of the filter->n_preds to zero from
the reallocation of preds for the filter, we can reset groups of
filters first, call synchronize_sched() just once, and then reallocate
each of the filters in the system group.

Cc: Tom Zanussi <tzanussi@xxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/trace/trace_events_filter.c | 80 ++++++++++++++++++++++++++++-------
1 files changed, 64 insertions(+), 16 deletions(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 932f605..1c14cf2 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -570,17 +570,28 @@ static void __free_preds(struct event_filter *filter)
filter->n_preds = 0;
}

+static void reset_preds(struct event_filter *filter)
+{
+ struct filter_pred *pred;
+ int n_preds = filter->n_preds;
+ int i;
+
+ filter->n_preds = 0;
+ if (!filter->preds)
+ return;
+
+ for (i = 0; i < n_preds; i++) {
+ pred = filter->preds[i];
+ pred->fn = filter_pred_none;
+ }
+}
+
static void filter_disable_preds(struct ftrace_event_call *call)
{
struct event_filter *filter = call->filter;
- int i;

call->flags &= ~TRACE_EVENT_FL_FILTERED;
- if (filter->preds) {
- for (i = 0; i < filter->n_preds; i++)
- filter->preds[i]->fn = filter_pred_none;
- }
- filter->n_preds = 0;
+ reset_preds(filter);
}

static void __free_filter(struct event_filter *filter)
@@ -620,15 +631,18 @@ static int __alloc_preds(struct event_filter *filter, int n_preds)

if (filter->preds) {
if (filter->a_preds < n_preds) {
- /* We need to reallocate */
- filter->n_preds = 0;
/*
- * It is possible that the filter is currently
- * being used. We need to zero out the number
- * of preds, wait on preemption and then free
- * the preds.
+ * We need to reallocate.
+ * We should have already have zeroed out
+ * the pred count and called synchronized_sched()
+ * to make sure no one is using the preds.
*/
synchronize_sched();
+ if (WARN_ON_ONCE(filter->n_preds)) {
+ /* We need to reset it now */
+ filter->n_preds = 0;
+ synchronize_sched();
+ }
__free_preds(filter);
}
}
@@ -1267,6 +1281,7 @@ static int replace_preds(struct ftrace_event_call *call,
return err;
}

+ n_preds = 0;
list_for_each_entry(elt, &ps->postfix, list) {
if (elt->op == OP_NONE) {
if (!operand1)
@@ -1327,6 +1342,30 @@ static int replace_system_preds(struct event_subsystem *system,
/* try to see if the filter can be applied */
err = replace_preds(call, filter, 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;
+
+ if (strcmp(call->class->system, system->name) != 0)
+ continue;
+
+ reset_preds(filter);
+ }
+
+ /*
+ * 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_for_each_entry(call, &ftrace_events, list) {
+ struct event_filter *filter = call->filter;
+
+ if (strcmp(call->class->system, system->name) != 0)
continue;

/* really apply the filter */
@@ -1341,11 +1380,13 @@ static int replace_system_preds(struct event_subsystem *system,
fail = false;
}

- if (fail) {
- parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
- return -EINVAL;
- }
+ if (fail)
+ goto fail;
+
return 0;
+ fail:
+ parse_error(ps, FILT_ERR_BAD_SUBSYS_FILTER, 0);
+ return -EINVAL;
}

int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
@@ -1380,6 +1421,13 @@ int apply_event_filter(struct ftrace_event_call *call, char *filter_string)
goto out;
}

+ /*
+ * Make sure all the pred counts are zero so that
+ * no task is using it when we reallocate the preds array.
+ */
+ reset_preds(call->filter);
+ synchronize_sched();
+
err = replace_preds(call, call->filter, ps, filter_string, false);
if (err)
append_filter_err(ps, call->filter);
--
1.7.2.3


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/