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authorSteven Rostedt <srostedt@redhat.com>2009-06-09 17:29:07 -0400
committerSteven Rostedt <rostedt@goodmis.org>2009-06-09 17:29:07 -0400
commit110bf2b764eb6026b868d84499263cb24b1bcc8d (patch)
tree66c869f6f96497051c4bda0797e234b3f7b39e8f /kernel/trace/trace_output.c
parent725c624a58a10ef90a2ff889e122158fabf36147 (diff)
tracing: add protection around module events unload
When reading the trace buffer, there is a race that when a module is unloaded it removes events that is stilled referenced in the buffers. This patch adds the protection around the unloading of the events from modules and the reading of the trace buffers. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/trace/trace_output.c')
-rw-r--r--kernel/trace/trace_output.c15
1 files changed, 12 insertions, 3 deletions
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index c05aff465dc..7938f3ae93e 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -14,7 +14,7 @@
/* must be a power of 2 */
#define EVENT_HASHSIZE 128
-static DECLARE_RWSEM(trace_event_mutex);
+DECLARE_RWSEM(trace_event_mutex);
DEFINE_PER_CPU(struct trace_seq, ftrace_event_seq);
EXPORT_PER_CPU_SYMBOL(ftrace_event_seq);
@@ -702,6 +702,16 @@ int register_ftrace_event(struct trace_event *event)
}
EXPORT_SYMBOL_GPL(register_ftrace_event);
+/*
+ * Used by module code with the trace_event_mutex held for write.
+ */
+int __unregister_ftrace_event(struct trace_event *event)
+{
+ hlist_del(&event->node);
+ list_del(&event->list);
+ return 0;
+}
+
/**
* unregister_ftrace_event - remove a no longer used event
* @event: the event to remove
@@ -709,8 +719,7 @@ EXPORT_SYMBOL_GPL(register_ftrace_event);
int unregister_ftrace_event(struct trace_event *event)
{
down_write(&trace_event_mutex);
- hlist_del(&event->node);
- list_del(&event->list);
+ __unregister_ftrace_event(event);
up_write(&trace_event_mutex);
return 0;