From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11975C43219 for ; Fri, 26 Apr 2019 15:47:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DBFF121537 for ; Fri, 26 Apr 2019 15:47:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726638AbfDZPrE (ORCPT ); Fri, 26 Apr 2019 11:47:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:50068 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726343AbfDZPrD (ORCPT ); Fri, 26 Apr 2019 11:47:03 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 77C7B214AE; Fri, 26 Apr 2019 15:47:02 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.92) (envelope-from ) id 1hK341-0002Mr-JL; Fri, 26 Apr 2019 11:47:01 -0400 Message-Id: <20190426154701.478779075@goodmis.org> User-Agent: quilt/0.65 Date: Fri, 26 Apr 2019 11:46:25 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Waiman Long , Linus Torvalds , Ingo Molnar , Will Deacon , Thomas Gleixner , the arch/x86 maintainers , Davidlohr Bueso , Tim Chen , huang ying , Roman Gushchin , Alexei Starovoitov , Daniel Borkmann , stable@vger.kernel.org, "Peter Zijlstra (Intel)" Subject: [for-linus][PATCH 3/3] trace: Fix preempt_enable_no_resched() abuse References: <20190426154622.183993476@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra Unless the very next line is schedule(), or implies it, one must not use preempt_enable_no_resched(). It can cause a preemption to go missing and thereby cause arbitrary delays, breaking the PREEMPT=y invariant. Link: http://lkml.kernel.org/r/20190423200318.GY14281@hirez.programming.kicks-ass.net Cc: Waiman Long Cc: Linus Torvalds Cc: Ingo Molnar Cc: Will Deacon Cc: Thomas Gleixner Cc: the arch/x86 maintainers Cc: Davidlohr Bueso Cc: Tim Chen Cc: huang ying Cc: Roman Gushchin Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: stable@vger.kernel.org Fixes: 2c2d7329d8af ("tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()") Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 41b6f96e5366..4ee8d8aa3d0f 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -762,7 +762,7 @@ u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) preempt_disable_notrace(); time = rb_time_stamp(buffer); - preempt_enable_no_resched_notrace(); + preempt_enable_notrace(); return time; } -- 2.20.1