tracing/filter: Call synchronize_sched() just once for system filters

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@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 63 insertions, 17 deletions

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index aac6a6183e6a..8f00a11ce778 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 +631,17 @@ 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);
                 }
         }
@@ -1328,6 +1341,30 @@ 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 */
@@ -1342,11 +1379,13 @@ 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)
@@ -1381,6 +1420,13 @@ 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);