From: Oleg Nesterov <oleg@redhat.com>
Date: Mon, 17 Jun 2013 17:02:07 +0000 (+0200)
Subject: tracing/syscall: Avoid perf_trace_buf_*() if sys_data->perf_events is empty
X-Git-Tag: v3.11-rc3~29^2~9
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=421c7860c6e1989da3962fafdd6699316c9f8e20;p=pandora-kernel.git

tracing/syscall: Avoid perf_trace_buf_*() if sys_data->perf_events is empty

perf_trace_buf_prepare() + perf_trace_buf_submit(head, task => NULL)
make no sense if hlist_empty(head). Change perf_syscall_enter/exit()
to check sys_data->{enter,exit}_event->perf_events beforehand.

Link: http://lkml.kernel.org/r/20130617170207.GA19806@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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