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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
parent725c624a58a10ef90a2ff889e122158fabf36147 (diff)
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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>
-rw-r--r--kernel/trace/trace_events.c4
-rw-r--r--kernel/trace/trace_output.c15
-rw-r--r--kernel/trace/trace_output.h4
3 files changed, 19 insertions, 4 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 6c81f9c..aa08be6 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1050,12 +1050,13 @@ static void trace_module_remove_events(struct module *mod)
struct ftrace_event_call *call, *p;
bool found = false;
+ down_write(&trace_event_mutex);
list_for_each_entry_safe(call, p, &ftrace_events, list) {
if (call->mod == mod) {
found = true;
ftrace_event_enable_disable(call, 0);
if (call->event)
- unregister_ftrace_event(call->event);
+ __unregister_ftrace_event(call->event);
debugfs_remove_recursive(call->dir);
list_del(&call->list);
trace_destroy_fields(call);
@@ -1079,6 +1080,7 @@ static void trace_module_remove_events(struct module *mod)
*/
if (found)
tracing_reset_current_online_cpus();
+ up_write(&trace_event_mutex);
}
static int trace_module_notify(struct notifier_block *self,
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index c05aff4..7938f3a 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;
diff --git a/kernel/trace/trace_output.h b/kernel/trace/trace_output.h
index ac240e7..d38bec4 100644
--- a/kernel/trace/trace_output.h
+++ b/kernel/trace/trace_output.h
@@ -27,6 +27,10 @@ extern struct trace_event *ftrace_find_event(int type);
extern enum print_line_t trace_nop_print(struct trace_iterator *iter,
int flags);
+/* used by module unregistering */
+extern int __unregister_ftrace_event(struct trace_event *event);
+extern struct rw_semaphore trace_event_mutex;
+
#define MAX_MEMHEX_BYTES 8
#define HEX_CHARS (MAX_MEMHEX_BYTES*2 + 1)