From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755399AbdERNic (ORCPT ); Thu, 18 May 2017 09:38:32 -0400 Received: from mail.kernel.org ([198.145.29.99]:41698 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932210AbdERNiO (ORCPT ); Thu, 18 May 2017 09:38:14 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D6C42399A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Thu, 18 May 2017 09:38:09 -0400 From: Steven Rostedt To: "Paul E. McKenney" Cc: LKML , Ingo Molnar , Thomas Gleixner Subject: [PATCH v2] tracing: Make sure RCU is watching before calling a stack trace Message-ID: <20170518093809.13428efa@gandalf.local.home> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" As stack tracing now requires "rcu watching", force RCU to be watching when recording a stack trace. Link: http://lkml.kernel.org/r/20170512172449.879684501@goodmis.org Cc: "Paul E. McKenney" Signed-off-by: Steven Rostedt (VMware) --- Changes since v1: My testing discovered that the stack trace can be called with interrupts enabled, which is a no no to have when calling rcu_irq_enter(). When interrupts are enabled, as with being in an NMI, RCU will also be watching. kernel/trace/trace.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index fcc9a2d..34a98ba 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2568,7 +2568,31 @@ static inline void ftrace_trace_stack(struct trace_array *tr, void __trace_stack(struct trace_array *tr, unsigned long flags, int skip, int pc) { - __ftrace_trace_stack(tr->trace_buffer.buffer, flags, skip, pc, NULL); + struct ring_buffer *buffer = tr->trace_buffer.buffer; + + /* + * When an NMI triggers, RCU is enabled via rcu_nmi_enter() + * Also, RCU is always enabled when interrupts are. + */ + if (!irqs_disabled() || in_nmi()) { + __ftrace_trace_stack(buffer, flags, skip, pc, NULL); + return; + } + + /* + * It is possible that a function is being traced in a + * location that RCU is not watching. A call to + * rcu_irq_enter() will make sure that it is, but there's + * a few internal rcu functions that could be traced + * where that wont work either. In those cases, we just + * do nothing. + */ + if (unlikely(rcu_irq_enter_disabled())) + return; + + rcu_irq_enter(); + __ftrace_trace_stack(buffer, flags, skip, pc, NULL); + rcu_irq_exit(); } /** -- 2.9.3