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=-6.0 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 C904FC04E53 for ; Wed, 15 May 2019 12:16:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9462920675 for ; Wed, 15 May 2019 12:16:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557922588; bh=PY83nNRfvy6AsMvB6zhM8qpy4kWbxWXj25HJ8FDV6TY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=NcZZaGOp8hLVmmijgtfiy6hFArkIsYz20NshG+Lfdn6n3KR/9qS89tazkgtmAZRVN 2nGMQlu3vSardMmGAWbNCXG9EEEImA4scxab4nSkBfFi1nET5JtWz/QbOEhniJdNUF bHoZ7QE/2cPUjJJzzaginGyP5iMrnnEJ/Lu3GZEE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728378AbfEOMQ1 (ORCPT ); Wed, 15 May 2019 08:16:27 -0400 Received: from mail.kernel.org ([198.145.29.99]:59864 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727105AbfEOLCd (ORCPT ); Wed, 15 May 2019 07:02:33 -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 44A5020644; Wed, 15 May 2019 11:02:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557918152; bh=PY83nNRfvy6AsMvB6zhM8qpy4kWbxWXj25HJ8FDV6TY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WaP4JCiPyOXLHU++UlUR8KZBpu1B2c7UYrg6NwQg8CsrH4M9NWaanAu3zKHK65CEX MjvskWQE5931ZhfMZA0mgoeuM6xLYoG909sNkgDiZo4Lud5oR8sgJ3VhtVhLW2S4J8 reaTMKvz+Z2w1PlLPIH5DFGaRuOUN9nvfsOxaCsc= 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 4.4 005/266] trace: Fix preempt_enable_no_resched() abuse Date: Wed, 15 May 2019 12:51:52 +0200 Message-Id: <20190515090722.861525812@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190515090722.696531131@linuxfoundation.org> References: <20190515090722.696531131@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 @@ -701,7 +701,7 @@ 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; }