[PATCH] tracing/filters: disallow concurrent/multiple setting/enabling of filters

[PATCH] tracing/filters: disallow concurrent/multiple setting/enabling of filters

[Tom Zanussi]

This patch disallows setting/enabling or multiple concurrent setting
and/or reading of event filters. 

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>

---
 kernel/trace/trace_events.c |   30 ++++++++++++++++++++++++++----
 1 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index be9299a..eb7ee65 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -481,7 +481,10 @@ event_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
 
 	trace_seq_init(s);
 
+	mutex_lock(&event_mutex);
 	filter_print_preds(call->preds, s);
+	mutex_unlock(&event_mutex);
+
 	r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);
 
 	kfree(s);
@@ -514,20 +517,28 @@ event_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
 		return err;
 	}
 
+	mutex_lock(&event_mutex);
 	if (pred->clear) {
 		filter_free_preds(call);
 		filter_free_pred(pred);
-		return cnt;
+		err = cnt;
+		goto out;
 	}
 
 	if (filter_add_pred(call, pred)) {
 		filter_free_pred(pred);
-		return -EINVAL;
+		err = -EINVAL;
+		goto out;
 	}
+	mutex_unlock(&event_mutex);
 
 	*ppos += cnt;
 
 	return cnt;
+
+out:
+	mutex_unlock(&event_mutex);
+	return err;
 }
 
 static ssize_t
@@ -547,7 +558,10 @@ subsystem_filter_read(struct file *filp, char __user *ubuf, size_t cnt,
 
 	trace_seq_init(s);
 
+	mutex_lock(&event_mutex);
 	filter_print_preds(system->preds, s);
+	mutex_unlock(&event_mutex);
+
 	r = simple_read_from_buffer(ubuf, cnt, ppos, s->buffer, s->len);
 
 	kfree(s);
@@ -580,21 +594,29 @@ subsystem_filter_write(struct file *filp, const char __user *ubuf, size_t cnt,
 		return err;
 	}
 
+	mutex_lock(&event_mutex);
 	if (pred->clear) {
 		filter_free_subsystem_preds(system);
 		filter_free_pred(pred);
-		return cnt;
+		err = cnt;
+		goto out;
 	}
 
 	if (filter_add_subsystem_pred(system, pred)) {
 		filter_free_subsystem_preds(system);
 		filter_free_pred(pred);
-		return -EINVAL;
+		err = -EINVAL;
+		goto out;
 	}
+	mutex_unlock(&event_mutex);
 
 	*ppos += cnt;
 
 	return cnt;
+
+out:
+	mutex_unlock(&event_mutex);
+	return err;
 }
 
 static const struct seq_operations show_event_seq_ops = {
-- 
1.5.6.3