Received: by 2002:a05:6a10:5bc5:0:0:0:0 with SMTP id os5csp2373311pxb; Tue, 12 Oct 2021 05:22:49 -0700 (PDT) X-Google-Smtp-Source: ABdhPJxhpjTkmQX/eE8kKd10C4wPlwC8U70W158ZcOoMZf9AmewCU2nyqTZBPDxF/r4GjsMdsfPM X-Received: by 2002:a17:906:2816:: with SMTP id r22mr33151213ejc.158.1634041368759; Tue, 12 Oct 2021 05:22:48 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1634041368; cv=none; d=google.com; s=arc-20160816; b=qlhTzL2vZ3r2Jz4tHI6Ufh1eglEQEThvVL/ol6yPfSJE92jbjgoZKifOUSJsgNlm0v RR3gLeojrnMcG1QrfCJuIr7Igs+qkmOALqUmOgbZYE8kdFmIMCpLXsfpmcOkfxiVzwNU 7LO4j315hgUb9HhEx0Bpx+Q+SVKNf9g5znCtAhgtlAwVErOGFONHXdjCSj7zPnp7VvUz p5C8x3J7rS+2NmPl2W1prvybEHid4gSGMlZ4s7G3hY/c8m+RvlYtCd9W+i874CyEqvsl CfonDnTrh9RE47cgGYfO9DORxkUOvt4OL05g+4kF2d5WxqWdICHCZCkONNZRYK8yKVc2 5uPQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:content-transfer-encoding:mime-version :references:in-reply-to:message-id:subject:cc:to:from:date; bh=/itJ3fFvWhECbJYDDMemyzgG5XiKu1wpGoakzIlqVHE=; b=byDWKySIKQKoj/szoyjbh/owCFP2hD6xElHC33bOcURiamot6yBTXPcIDqJeZIbAOD EHRXj0wULFAPzp6iUFKLerSk//ZnoureYlWdRtQTa8gMjjnj1d8dbh4rLvhZTcXXqbbG SZJhV/Wv50ZvvW5V1v4R9fUC+M8Fi5CttbJhUEWLg2PXjxgcBNxNQ6+89i/pVYEi4sXx AlOrMGwtsmFBjAIi3YGGBvhbNZPeGNm6XpeiSSoQRkPMf01mYsQZGGs0RTSkrtOsGOQp B/VnnqZRlMpUBBi19s6eDpRKVMF+USBYxfsEy+JFKsO61xTlNgknzEF2TvI5z7TTdfwv EcNQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id d11si19920526edm.216.2021.10.12.05.22.16; Tue, 12 Oct 2021 05:22:48 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236325AbhJLMTg convert rfc822-to-8bit (ORCPT + 99 others); Tue, 12 Oct 2021 08:19:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:53206 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236196AbhJLMTe (ORCPT ); Tue, 12 Oct 2021 08:19:34 -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 DD5ED60E97; Tue, 12 Oct 2021 12:17:29 +0000 (UTC) Date: Tue, 12 Oct 2021 08:17:28 -0400 From: Steven Rostedt To: =?UTF-8?B?546L6LSH?= Cc: Guo Ren , Ingo Molnar , "James E.J. Bottomley" , Helge Deller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Paul Walmsley , Palmer Dabbelt , Albert Ou , Thomas Gleixner , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , Josh Poimboeuf , Jiri Kosina , Miroslav Benes , Petr Mladek , Joe Lawrence , Colin Ian King , Masami Hiramatsu , "Peter Zijlstra (Intel)" , Nicholas Piggin , Jisheng Zhang , linux-csky@vger.kernel.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, live-patching@vger.kernel.org Subject: Re: [PATCH 1/2] ftrace: disable preemption on the testing of recursion Message-ID: <20211012081728.5d357d6c@gandalf.local.home> In-Reply-To: References: <8c7de46d-9869-aa5e-2bb9-5dbc2eda395e@linux.alibaba.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Oct 2021 13:40:08 +0800 王贇 wrote: > @@ -52,11 +52,6 @@ static void notrace klp_ftrace_handler(unsigned long ip, > bit = ftrace_test_recursion_trylock(ip, parent_ip); > if (WARN_ON_ONCE(bit < 0)) > return; > - /* > - * A variant of synchronize_rcu() is used to allow patching functions > - * where RCU is not watching, see klp_synchronize_transition(). > - */ I have to take a deeper look at this patch set, but do not remove this comment, as it explains the protection here, that is not obvious with the changes you made. -- Steve > - preempt_disable_notrace(); > > func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, > stack_node);