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=-12.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_PASS 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 E7064C43219 for ; Mon, 29 Apr 2019 13:31:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B90372084B for ; Mon, 29 Apr 2019 13:31:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728321AbfD2NbV (ORCPT ); Mon, 29 Apr 2019 09:31:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:35648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726321AbfD2NbV (ORCPT ); Mon, 29 Apr 2019 09:31:21 -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 004C520652; Mon, 29 Apr 2019 13:31:18 +0000 (UTC) Date: Mon, 29 Apr 2019 09:31:17 -0400 From: Steven Rostedt To: tip-bot for Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, guro@fb.com, peterz@infradead.org, hpa@zytor.com, dave@stgolabs.net, tim.c.chen@linux.intel.com, rostedt@goodmis.org, ast@kernel.org, torvalds@linux-foundation.org, longman@redhat.com, will.deacon@arm.com, huang.ying.caritas@gmail.com, daniel@iogearbox.net, tglx@linutronix.de, linux-tip-commits@vger.kernel.org Subject: Re: [tip:sched/core] trace: Fix preempt_enable_no_resched() abuse Message-ID: <20190429093117.23760399@gandalf.local.home> In-Reply-To: References: <20190423200318.GY14281@hirez.programming.kicks-ass.net> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 28 Apr 2019 23:39:03 -0700 tip-bot for Peter Zijlstra wrote: > Commit-ID: e8bd5814989b994cf1b0cb179e1c777e40c0f02c > Gitweb: https://git.kernel.org/tip/e8bd5814989b994cf1b0cb179e1c777e40c0f02c > Author: Peter Zijlstra > AuthorDate: Tue, 23 Apr 2019 22:03:18 +0200 > Committer: Ingo Molnar > CommitDate: Mon, 29 Apr 2019 08:27:09 +0200 > > trace: Fix preempt_enable_no_resched() abuse Hi Ingo, I already sent this fix to Linus, and it's been pulled in to his tree. Commit: d6097c9e4454adf1f8f2c9547c2fa6060d55d952 -- Steve > > Unless there is a call into schedule() in the immediate > (deterministic) future, 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. > > Signed-off-by: Peter Zijlstra (Intel) > Cc: Alexei Starovoitov > Cc: Daniel Borkmann > Cc: Davidlohr Bueso > Cc: Linus Torvalds > Cc: Roman Gushchin > Cc: Steven Rostedt > Cc: Thomas Gleixner > Cc: Tim Chen > Cc: Waiman Long > Cc: Will Deacon > Cc: huang ying > Fixes: 2c2d7329d8af ("tracing/ftrace: use preempt_enable_no_resched_notrace in ring_buffer_time_stamp()") > Link: https://lkml.kernel.org/r/20190423200318.GY14281@hirez.programming.kicks-ass.net > Signed-off-by: Ingo Molnar > --- > 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; > }