From b8ebfd3f7113b63dda93d76bfec638c00e6bd514 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Mon, 17 Jun 2013 19:02:04 +0200
Subject: [PATCH] tracing/function: Avoid perf_trace_buf_*() if
 event_function.perf_events is empty

perf_trace_buf_prepare() + perf_trace_buf_submit(head, task => NULL)
make no sense if hlist_empty(head). Change perf_ftrace_function_call()
to check event_function.perf_events beforehand.

Link: http://lkml.kernel.org/r/20130617170204.GA19803@redhat.com

Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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