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authorSteven Rostedt <srostedt@redhat.com>2009-04-24 12:20:52 -0400
committerSteven Rostedt <rostedt@goodmis.org>2009-04-24 23:06:00 -0400
commit060fa5c83e67901ba47ab484cfcdb32737d630ba (patch)
treec83ec27ae1064cfb290904f95cb85b3b0889b2a1
parentb8e65554d80b4c560d201362d0e8fa02109d89fd (diff)
tracing/events: reuse trace event ids after overflow
With modules being able to add trace events, and the max trace event counter is 16 bits (65536) we can overflow the counter easily with a simple while loop adding and removing modules that contain trace events. This patch links together the registered trace events and on overflow searches for available trace event ids. It will still fail if over 65536 events are registered, but considering that a typical kernel only has 22000 functions, 65000 events should be sufficient. Reported-by: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
-rw-r--r--include/linux/ftrace_event.h1
-rw-r--r--kernel/trace/trace_output.c71
2 files changed, 61 insertions, 11 deletions
diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
index 07e0a6d64a2..78a9ba24cbf 100644
--- a/include/linux/ftrace_event.h
+++ b/include/linux/ftrace_event.h
@@ -56,6 +56,7 @@ typedef enum print_line_t (*trace_print_func)(struct trace_iterator *iter,
int flags);
struct trace_event {
struct hlist_node node;
+ struct list_head list;
int type;
trace_print_func trace;
trace_print_func raw;
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 06997e75114..5fc51f0f75f 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -483,6 +483,36 @@ struct trace_event *ftrace_find_event(int type)
return NULL;
}
+static LIST_HEAD(ftrace_event_list);
+
+static int trace_search_list(struct list_head **list)
+{
+ struct trace_event *e;
+ int last = __TRACE_LAST_TYPE;
+
+ if (list_empty(&ftrace_event_list)) {
+ *list = &ftrace_event_list;
+ return last + 1;
+ }
+
+ /*
+ * We used up all possible max events,
+ * lets see if somebody freed one.
+ */
+ list_for_each_entry(e, &ftrace_event_list, list) {
+ if (e->type != last + 1)
+ break;
+ last++;
+ }
+
+ /* Did we used up all 65 thousand events??? */
+ if ((last + 1) > FTRACE_MAX_EVENT)
+ return 0;
+
+ *list = &e->list;
+ return last + 1;
+}
+
/**
* register_ftrace_event - register output for an event type
* @event: the event type to register
@@ -505,20 +535,40 @@ int register_ftrace_event(struct trace_event *event)
mutex_lock(&trace_event_mutex);
- if (!event) {
- ret = next_event_type++;
+ if (WARN_ON(!event))
goto out;
- }
- if (!event->type)
- event->type = next_event_type++;
- else if (event->type > __TRACE_LAST_TYPE) {
+ INIT_LIST_HEAD(&event->list);
+
+ if (!event->type) {
+ struct list_head *list;
+
+ if (next_event_type > FTRACE_MAX_EVENT) {
+
+ event->type = trace_search_list(&list);
+ if (!event->type)
+ goto out;
+
+ } else {
+
+ event->type = next_event_type++;
+ list = &ftrace_event_list;
+ }
+
+ if (WARN_ON(ftrace_find_event(event->type)))
+ goto out;
+
+ list_add_tail(&event->list, list);
+
+ } else if (event->type > __TRACE_LAST_TYPE) {
printk(KERN_WARNING "Need to add type to trace.h\n");
WARN_ON(1);
- }
-
- if (ftrace_find_event(event->type))
goto out;
+ } else {
+ /* Is this event already used */
+ if (ftrace_find_event(event->type))
+ goto out;
+ }
if (event->trace == NULL)
event->trace = trace_nop_print;
@@ -537,8 +587,6 @@ int register_ftrace_event(struct trace_event *event)
out:
mutex_unlock(&trace_event_mutex);
- WARN_ON_ONCE(next_event_type > FTRACE_MAX_EVENT);
-
return ret;
}
EXPORT_SYMBOL_GPL(register_ftrace_event);
@@ -551,6 +599,7 @@ int unregister_ftrace_event(struct trace_event *event)
{
mutex_lock(&trace_event_mutex);
hlist_del(&event->node);
+ list_del(&event->list);
mutex_unlock(&trace_event_mutex);
return 0;