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=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 AA386C433ED for ; Fri, 30 Apr 2021 02:47:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 84548611CB for ; Fri, 30 Apr 2021 02:47:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229951AbhD3Csf (ORCPT ); Thu, 29 Apr 2021 22:48:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:45916 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229591AbhD3Cse (ORCPT ); Thu, 29 Apr 2021 22:48:34 -0400 Received: from oasis.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 A4CF561406; Fri, 30 Apr 2021 02:47:44 +0000 (UTC) Date: Thu, 29 Apr 2021 22:47:42 -0400 From: Steven Rostedt To: Changbin Du Cc: Palmer Dabbelt , linux-riscv@lists.infradead.org, Paul Walmsley , aou@eecs.berkeley.edu, peterz@infradead.org, jpoimboe@redhat.com, jbaron@akamai.com, ardb@kernel.org, Atish Patra , Anup Patel , akpm@linux-foundation.org, rppt@kernel.org, mhiramat@kernel.org, zong.li@sifive.com, guoren@linux.alibaba.com, wangkefeng.wang@huawei.com, 0x7f454c46@gmail.com, chenhuang5@huawei.com, linux-kernel@vger.kernel.org, kernel-team@android.com, Palmer Dabbelt Subject: Re: [PATCH] RISC-V: insn: Use a raw spinlock to protect TEXT_POKE* Message-ID: <20210429224742.391154ae@oasis.local.home> In-Reply-To: <20210429215451.yuey5gzmfh2dkzp5@mail.google.com> References: <20210429061713.783628-1-palmer@dabbelt.com> <20210429123007.5144fc0d@gandalf.local.home> <20210429215451.yuey5gzmfh2dkzp5@mail.google.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 30 Apr 2021 05:54:51 +0800 Changbin Du wrote: > The problem is that lockdep cannot handle locks across tasks since we use > stopmachine to patch code for risc-v. So there's a false positive report. > See privious disscussion here: > https://lkml.org/lkml/2021/4/29/63 Please use lore.kernel.org, lkml.org is highly unreliable, and is considered deprecated for use of referencing linux kernel archives. Would the following patch work? (note, I did not even compile test it) -- Steve diff --git a/arch/riscv/include/asm/ftrace.h b/arch/riscv/include/asm/ftrace.h index 845002cc2e57..19acbb4aaeff 100644 --- a/arch/riscv/include/asm/ftrace.h +++ b/arch/riscv/include/asm/ftrace.h @@ -25,6 +25,8 @@ struct dyn_arch_ftrace { }; #endif +extern int running_ftrace; + #ifdef CONFIG_DYNAMIC_FTRACE /* * A general call in RISC-V is a pair of insts: diff --git a/arch/riscv/kernel/ftrace.c b/arch/riscv/kernel/ftrace.c index 7f1e5203de88..834ab4fad637 100644 --- a/arch/riscv/kernel/ftrace.c +++ b/arch/riscv/kernel/ftrace.c @@ -11,15 +11,19 @@ #include #include +int running_ftrace; + #ifdef CONFIG_DYNAMIC_FTRACE int ftrace_arch_code_modify_prepare(void) __acquires(&text_mutex) { mutex_lock(&text_mutex); + running_ftrace = 1; return 0; } int ftrace_arch_code_modify_post_process(void) __releases(&text_mutex) { + running_ftrace = 0; mutex_unlock(&text_mutex); return 0; } diff --git a/arch/riscv/kernel/patch.c b/arch/riscv/kernel/patch.c index 0b552873a577..4cd1c79a9689 100644 --- a/arch/riscv/kernel/patch.c +++ b/arch/riscv/kernel/patch.c @@ -12,6 +12,7 @@ #include #include #include +#include struct patch_insn { void *addr; @@ -59,8 +60,13 @@ static int patch_insn_write(void *addr, const void *insn, size_t len) * Before reaching here, it was expected to lock the text_mutex * already, so we don't need to give another lock here and could * ensure that it was safe between each cores. + * + * ftrace uses stop machine, and even though the text_mutex is + * held, the stop machine task that calls this function will not + * be the owner. */ - lockdep_assert_held(&text_mutex); + if (!running_ftrace) + lockdep_assert_held(&text_mutex); if (across_pages) patch_map(addr + len, FIX_TEXT_POKE1);