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=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 1D53CC433E0 for ; Wed, 3 Jun 2020 09:59:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EADB82074B for ; Wed, 3 Jun 2020 09:59:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591178375; bh=IzFcQybnWhy0o7ePqiwAbjE20V7uSYo4yk8k+ca5LWk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=Tk+OWAizMna2ZtTjwYURz8Y0fGapfL0YqV+fN2tEdOOeQac4zjLKDlILlUiwY90Tl XDp7MlXm4crOi7rvGR0Yp0IqKs4Ex96wH6t4HpraSIGgGMXO8l2SmSOlSrTe3g6kaj C3u48DDYZTGIuTEPDc/JupFb11pRF5DikKQBZSGM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726711AbgFCJ7e (ORCPT ); Wed, 3 Jun 2020 05:59:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:33512 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726597AbgFCJ7d (ORCPT ); Wed, 3 Jun 2020 05:59:33 -0400 Received: from paulmck-ThinkPad-P72.home (50-39-105-78.bvtn.or.frontiernet.net [50.39.105.78]) (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 B958720734; Wed, 3 Jun 2020 09:59:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1591178372; bh=IzFcQybnWhy0o7ePqiwAbjE20V7uSYo4yk8k+ca5LWk=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=CQ3ENkUih/3yjm1HsvrgHxRFdP0J+pqYjVui3V8pACDoR3+bOLRkFFB5AqJuFcVux fiusxdVBIYjeKlCCoJ/CIuX77dIcjSX8+uZW+9JhosSKeq1L2IhtxPZj+K7+BvMivd nrOmok80cpMvuVjrbdQoaIErxOFS1Ve3xI06Tcq4= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 9D36D352281E; Wed, 3 Jun 2020 02:59:32 -0700 (PDT) Date: Wed, 3 Jun 2020 02:59:32 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Marco Elver , Nick Desaulniers , Will Deacon , Borislav Petkov , Thomas Gleixner , Ingo Molnar , clang-built-linux , Dmitry Vyukov , Alexander Potapenko , Andrey Konovalov , kasan-dev , LKML Subject: Re: [PATCH] rcu: Fixup noinstr warnings Message-ID: <20200603095932.GM29598@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20200602184409.22142-1-elver@google.com> <20200602191936.GE2604@hirez.programming.kicks-ass.net> <20200602193853.GF2604@hirez.programming.kicks-ass.net> <20200603084818.GB2627@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200603084818.GB2627@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 03, 2020 at 10:48:18AM +0200, Peter Zijlstra wrote: > On Tue, Jun 02, 2020 at 09:38:53PM +0200, Peter Zijlstra wrote: > > > That said; noinstr's __no_sanitize combined with atomic_t might be > > 'interesting', because the regular atomic things have explicit > > annotations in them. That should give validation warnings for the right > > .config, I'll have to go try -- so far I've made sure to never enable > > the *SAN stuff. > > --- > Subject: rcu: Fixup noinstr warnings > > A KCSAN build revealed we have explicit annoations through atomic_t > usage, switch to arch_atomic_*() for the respective functions. > > vmlinux.o: warning: objtool: rcu_nmi_exit()+0x4d: call to __kcsan_check_access() leaves .noinstr.text section > vmlinux.o: warning: objtool: rcu_dynticks_eqs_enter()+0x25: call to __kcsan_check_access() leaves .noinstr.text section > vmlinux.o: warning: objtool: rcu_nmi_enter()+0x4f: call to __kcsan_check_access() leaves .noinstr.text section > vmlinux.o: warning: objtool: rcu_dynticks_eqs_exit()+0x2a: call to __kcsan_check_access() leaves .noinstr.text section > vmlinux.o: warning: objtool: __rcu_is_watching()+0x25: call to __kcsan_check_access() leaves .noinstr.text section > > Signed-off-by: Peter Zijlstra (Intel) This one does not apply cleanly onto the -rcu tree's "dev" branch, so I am guessing that it is intended to be carried in -tip with yours and Thomas's patch series. If you do instead want this in -rcu, please let me know. Thanx, Paul > --- > kernel/rcu/tree.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index c716eadc7617..162656b80db9 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -250,7 +250,7 @@ static noinstr void rcu_dynticks_eqs_enter(void) > * next idle sojourn. > */ > rcu_dynticks_task_trace_enter(); // Before ->dynticks update! > - seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); > + seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); > // RCU is no longer watching. Better be in extended quiescent state! > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && > (seq & RCU_DYNTICK_CTRL_CTR)); > @@ -274,13 +274,13 @@ static noinstr void rcu_dynticks_eqs_exit(void) > * and we also must force ordering with the next RCU read-side > * critical section. > */ > - seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); > + seq = arch_atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); > // RCU is now watching. Better not be in an extended quiescent state! > rcu_dynticks_task_trace_exit(); // After ->dynticks update! > WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && > !(seq & RCU_DYNTICK_CTRL_CTR)); > if (seq & RCU_DYNTICK_CTRL_MASK) { > - atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks); > + arch_atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks); > smp_mb__after_atomic(); /* _exit after clearing mask. */ > } > } > @@ -313,7 +313,7 @@ static __always_inline bool rcu_dynticks_curr_cpu_in_eqs(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > > - return !(atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR); > + return !(arch_atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR); > } > > /* > @@ -692,6 +692,7 @@ noinstr void rcu_nmi_exit(void) > { > struct rcu_data *rdp = this_cpu_ptr(&rcu_data); > > + instrumentation_begin(); > /* > * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. > * (We are exiting an NMI handler, so RCU better be paying attention > @@ -705,7 +706,6 @@ noinstr void rcu_nmi_exit(void) > * leave it in non-RCU-idle state. > */ > if (rdp->dynticks_nmi_nesting != 1) { > - instrumentation_begin(); > trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, > atomic_read(&rdp->dynticks)); > WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ > @@ -714,7 +714,6 @@ noinstr void rcu_nmi_exit(void) > return; > } > > - instrumentation_begin(); > /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ > trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks)); > WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */