From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752051AbdIWU67 (ORCPT ); Sat, 23 Sep 2017 16:58:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:59298 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751578AbdIWU6G (ORCPT ); Sat, 23 Sep 2017 16:58:06 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 94DDE21889 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 Message-Id: <20170923205804.541902059@goodmis.org> User-Agent: quilt/0.63-1 Date: Sat, 23 Sep 2017 16:56:25 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton , "Paul E. McKenney" , stable@vger.kernel.org Subject: [PATCH 4/4] tracing: Remove RCU work arounds from stack tracer References: <20170923205621.811805556@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Disposition: inline; filename=0004-tracing-Remove-RCU-work-arounds-from-stack-tracer.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Steven Rostedt (VMware)" Currently the stack tracer calls rcu_irq_enter() to make sure RCU is watching when it records a stack trace. But if the stack tracer is triggered while tracing inside of a rcu_irq_enter(), calling rcu_irq_enter() unconditionally can be problematic. The reason for having rcu_irq_enter() in the first place has been fixed from within the saving of the stack trace code, and there's no reason for doing it in the stack tracer itself. Just remove it. Cc: stable@vger.kernel.org Fixes: 0be964be0 ("module: Sanitize RCU usage and locking") Acked-by: Paul E. McKenney Suggested-by: "Paul E. McKenney" Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_stack.c | 15 --------------- 1 file changed, 15 deletions(-) diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index a4df67cbc711..49cb41412eec 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -96,23 +96,9 @@ check_stack(unsigned long ip, unsigned long *stack) if (in_nmi()) return; - /* - * There's a slight chance that we are tracing inside the - * RCU infrastructure, and rcu_irq_enter() will not work - * as expected. - */ - if (unlikely(rcu_irq_enter_disabled())) - return; - local_irq_save(flags); arch_spin_lock(&stack_trace_max_lock); - /* - * RCU may not be watching, make it see us. - * The stack trace code uses rcu_sched. - */ - rcu_irq_enter(); - /* In case another CPU set the tracer_frame on us */ if (unlikely(!frame_size)) this_size -= tracer_frame; @@ -205,7 +191,6 @@ check_stack(unsigned long ip, unsigned long *stack) } out: - rcu_irq_exit(); arch_spin_unlock(&stack_trace_max_lock); local_irq_restore(flags); } -- 2.13.2