Commit 2816c551 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
Browse files

tracing: trace_remove_event_call() should fail if call/file is in use 

Change trace_remove_event_call(call) to return the error if this
call is active. This is what the callers assume but can't verify
outside of the tracing locks. Both trace_kprobe.c/trace_uprobe.c
need the additional changes, unregister_trace_probe() should abort
if trace_remove_event_call() fails.

The caller is going to free this call/file so we must ensure that
nobody can use them after trace_remove_event_call() succeeds.
debugfs should be fine after the previous changes and event_remove()
does TRACE_REG_UNREGISTER, but still there are 2 reasons why we need
the additional checks:

- There could be a perf_event(s) attached to this tp_event, so the
  patch checks ->perf_refcount.

- TRACE_REG_UNREGISTER can be suppressed by FTRACE_EVENT_FL_SOFT_MODE,
  so we simply check FTRACE_EVENT_FL_ENABLED protected by event_mutex.

Link: http://lkml.kernel.org/r/20130729175033.GB26284@redhat.com



Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 776164c1

include/linux/ftrace_event.h

+1 −1
Original line number Diff line number Diff line
@@ -332,7 +332,7 @@ extern int trace_define_field(struct ftrace_event_call *call, const char *type, 
			      const char *name, int offset, int size,

			      int is_signed, int filter_type);

extern int trace_add_event_call(struct ftrace_event_call *call);

extern void trace_remove_event_call(struct ftrace_event_call *call);

extern int trace_remove_event_call(struct ftrace_event_call *call);



#define is_signed_type(type)	(((type)(-1)) < (type)1)

kernel/trace/trace_events.c

+33 −2
Original line number Diff line number Diff line
@@ -1713,16 +1713,47 @@ static void __trace_remove_event_call(struct ftrace_event_call *call) 
	destroy_preds(call);

}



static int probe_remove_event_call(struct ftrace_event_call *call)

{

	struct trace_array *tr;

	struct ftrace_event_file *file;



#ifdef CONFIG_PERF_EVENTS

	if (call->perf_refcount)

		return -EBUSY;

#endif

	do_for_each_event_file(tr, file) {

		if (file->event_call != call)

			continue;

		/*

		 * We can't rely on ftrace_event_enable_disable(enable => 0)

		 * we are going to do, FTRACE_EVENT_FL_SOFT_MODE can suppress

		 * TRACE_REG_UNREGISTER.

		 */

		if (file->flags & FTRACE_EVENT_FL_ENABLED)

			return -EBUSY;

		break;

	} while_for_each_event_file();



	__trace_remove_event_call(call);



	return 0;

}



/* Remove an event_call */

void trace_remove_event_call(struct ftrace_event_call *call)

int trace_remove_event_call(struct ftrace_event_call *call)

{

	int ret;



	mutex_lock(&trace_types_lock);

	mutex_lock(&event_mutex);

	down_write(&trace_event_sem);

	__trace_remove_event_call(call);

	ret = probe_remove_event_call(call);

	up_write(&trace_event_sem);

	mutex_unlock(&event_mutex);

	mutex_unlock(&trace_types_lock);



	return ret;

}



#define for_each_event(event, start, end)			\

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