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>

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index aac6a6183e6a371fe7dfbdfb83057dbe87b4a485..8f00a11ce7788739ceff318a4b86524d1c6bbbab 100644 (file)
--- 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);