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=-6.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 AEBAAC04AA6 for ; Tue, 30 Apr 2019 11:44:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7EA30217D6 for ; Tue, 30 Apr 2019 11:44:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556624682; bh=vcfxo2TFke0cuyMwibf/eIW/V6zVHCpZXvsgz4Sm4gY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=netkt6I3UP6xPLHlJxuxTQdRU5//Fnlrvt4j4XKYAm3lU8H1Gxwh3lDJmCGYOyt5j MJdwuOQHsMi25Hea3ARl3CCptnL9/QDd3+rCJ3eh8hYsEQw4KLYKBZnP4AaG+KT7Vc LpOa5kQvuMGke/Ge7qFPNDRDf4R0YJt1+0LCY+js= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729312AbfD3Lol (ORCPT ); Tue, 30 Apr 2019 07:44:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:56210 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729295AbfD3Lok (ORCPT ); Tue, 30 Apr 2019 07:44:40 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 DD71721670; Tue, 30 Apr 2019 11:44:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556624679; bh=vcfxo2TFke0cuyMwibf/eIW/V6zVHCpZXvsgz4Sm4gY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vnizXFoWTI0oZuP9hsB6DJ1iJT0SlfA/RzaAUvCNwtmT+NWroPx8kN7u/H/Sqr1vc PYBuquELVtyvF2v4+Dl/2uf39ppHQ0WdKph9wysgk6vT011Vh84jscxOb2kAxguPuy JMFxN61szIFjEz4+9l8Lv2YQoB9VYRfX0RfAaeKg= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, 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 , "Peter Zijlstra (Intel)" , "Steven Rostedt (VMware)" Subject: [PATCH 4.19 031/100] trace: Fix preempt_enable_no_resched() abuse Date: Tue, 30 Apr 2019 13:38:00 +0200 Message-Id: <20190430113610.291111512@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190430113608.616903219@linuxfoundation.org> References: <20190430113608.616903219@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Peter Zijlstra commit d6097c9e4454adf1f8f2c9547c2fa6060d55d952 upstream. 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) Signed-off-by: Greg Kroah-Hartman --- kernel/trace/ring_buffer.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -730,7 +730,7 @@ u64 ring_buffer_time_stamp(struct ring_b preempt_disable_notrace(); time = rb_time_stamp(buffer); - preempt_enable_no_resched_notrace(); + preempt_enable_notrace(); return time; }