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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3A49DC433F5 for ; Thu, 14 Oct 2021 09:22:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1CAA86109E for ; Thu, 14 Oct 2021 09:22:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229468AbhJNJY4 (ORCPT ); Thu, 14 Oct 2021 05:24:56 -0400 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:39240 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229967AbhJNJYz (ORCPT ); Thu, 14 Oct 2021 05:24:55 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R101e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=yun.wang@linux.alibaba.com;NM=1;PH=DS;RN=31;SR=0;TI=SMTPD_---0UrnMW2X_1634203363; Received: from testdeMacBook-Pro.local(mailfrom:yun.wang@linux.alibaba.com fp:SMTPD_---0UrnMW2X_1634203363) by smtp.aliyun-inc.com(127.0.0.1); Thu, 14 Oct 2021 17:22:45 +0800 Subject: Re: [PATCH v3 1/2] ftrace: disable preemption between ftrace_test_recursion_trylock/unlock() To: Miroslav Benes Cc: Guo Ren , Steven Rostedt , 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 , 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 References: <609b565a-ed6e-a1da-f025-166691b5d994@linux.alibaba.com> <7e4738b5-21d4-c4d0-3136-a096bbb5cd2c@linux.alibaba.com> From: =?UTF-8?B?546L6LSH?= Message-ID: Date: Thu, 14 Oct 2021 17:22:43 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 2021/10/14 下午5:13, Miroslav Benes wrote: >> diff --git a/kernel/livepatch/patch.c b/kernel/livepatch/patch.c >> index e8029ae..b8d75fb 100644 >> --- a/kernel/livepatch/patch.c >> +++ b/kernel/livepatch/patch.c >> @@ -49,14 +49,16 @@ static void notrace klp_ftrace_handler(unsigned long ip, >> >> ops = container_of(fops, struct klp_ops, fops); >> >> + /* >> + * > > This empty line is not useful. > >> + * The ftrace_test_recursion_trylock() will disable preemption, >> + * which is required for the variant of synchronize_rcu() that is >> + * used to allow patching functions where RCU is not watching. >> + * See klp_synchronize_transition() for more details. >> + */ >> 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(). >> - */ >> - preempt_disable_notrace(); >> >> func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, >> stack_node); >> @@ -120,7 +122,6 @@ static void notrace klp_ftrace_handler(unsigned long ip, >> klp_arch_set_pc(fregs, (unsigned long)func->new_func); >> >> unlock: >> - preempt_enable_notrace(); >> ftrace_test_recursion_unlock(bit); >> } > > Acked-by: Miroslav Benes > > for the livepatch part of the patch. > > I would also ask you not to submit new versions so often, so that the > other reviewers have time to actually review the patch set. > > Quoting from Documentation/process/submitting-patches.rst: > > "Wait for a minimum of one week before resubmitting or pinging reviewers - > possibly longer during busy times like merge windows." Thanks for the Ack and suggestion, will take care from now on :-) Regards, Michael Wang > > Thanks > > Miroslav >