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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 60FCDC4332F for ; Thu, 20 Oct 2022 22:27:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229667AbiJTW1Y (ORCPT ); Thu, 20 Oct 2022 18:27:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229489AbiJTW1W (ORCPT ); Thu, 20 Oct 2022 18:27:22 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0D98922BAC9; Thu, 20 Oct 2022 15:27:21 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id CB342B8238D; Thu, 20 Oct 2022 22:27:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7CB16C433D6; Thu, 20 Oct 2022 22:27:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666304838; bh=Hplm7yNv/x7EyeXp8SfEb20uj/fqyD9O6uJA3g5LIrI=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=vJ8sA+wiQF4XIzA+76+EQxH5rvFbrJDxIsxHj5Rp+iJ/n4t+dQSRas9krLQmExXWj DxzJPCbEAi5fE8d64TvDhBERvhy5Ai3sP339Z/J7aEbr/ERR3xZvl2k4QhuZZNWJAm mhTbY3UVicyH61NAL5n71UaYjWqd8KqyqODlSfaq/Hq64gYkNWweKdaOrYEMND1Ndg RjeEI2nDQgvsWh/IQql6INCiQcmsYG5aMMxN7lAPyoRElI6g1GW1rn26PAkaNi2kBc UqaedyD/A11SXRYzuKF7uCjDDmIqTTahVW+WoDAlTF30JS2Ii25TuBsVqalT/Umej7 w5YwR0CVrhxPg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 1D8B15C1109; Thu, 20 Oct 2022 15:27:18 -0700 (PDT) Date: Thu, 20 Oct 2022 15:27:18 -0700 From: "Paul E. McKenney" To: Frederic Weisbecker Cc: John Ogness , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, tglx@linutronix.de, pmladek@suse.com Subject: Re: [PATCH v2 rcu 0/8] NMI-safe SRCU reader API Message-ID: <20221020222718.GA5600@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20220921144620.GA1200846@paulmck-ThinkPad-P17-Gen-1> <20220929180714.GA2874192@paulmck-ThinkPad-P17-Gen-1> <87k04x4e0r.fsf@jogness.linutronix.de> <20221018152418.GR5600@paulmck-ThinkPad-P17-Gen-1> <87ilkh0y52.fsf@jogness.linutronix.de> <20221018185936.GX5600@paulmck-ThinkPad-P17-Gen-1> <20221018215721.GA1716567@paulmck-ThinkPad-P17-Gen-1> <87pmeoawwe.fsf@jogness.linutronix.de> <20221019191418.GF5600@paulmck-ThinkPad-P17-Gen-1> <20221019220537.GA1234896@lothringen> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221019220537.GA1234896@lothringen> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 20, 2022 at 12:05:37AM +0200, Frederic Weisbecker wrote: > On Wed, Oct 19, 2022 at 12:14:18PM -0700, Paul E. McKenney wrote: > > On Wed, Oct 19, 2022 at 01:19:53PM +0206, John Ogness wrote: > > > On 2022-10-18, "Paul E. McKenney" wrote: > > > > And the v6.1-rc1 stack is now at srcunmisafe.2022.10.18b. > > > > > > Thanks! > > > > > > I guess the kernel test robot will catch this, but if you checkout > > > commit 79c95dc428ad ("arch/x86: Add ARCH_HAS_NMI_SAFE_THIS_CPU_OPS > > > Kconfig option") and build for x86_64, you will get: > > > > > > x86_64-linux-gnu-ld: kernel/rcu/srcutree.o: in function `srcu_gp_start_if_needed': > > > srcutree.c:(.text+0x133a): undefined reference to `__srcu_read_lock_nmisafe' > > > x86_64-linux-gnu-ld: srcutree.c:(.text+0x1490): undefined reference to `__srcu_read_unlock_nmisafe' > > > x86_64-linux-gnu-ld: kernel/rcu/srcutree.o: in function `srcu_barrier': > > > srcutree.c:(.text+0x1b03): undefined reference to `__srcu_read_lock_nmisafe' > > > x86_64-linux-gnu-ld: srcutree.c:(.text+0x1b38): undefined reference to `__srcu_read_unlock_nmisafe' > > > > > > Note that this error is fixed with a later commit: > > > > > > commit c2d158a284ab ("srcu: Debug NMI safety even on archs that don't > > > require it"). > > > > > > This does not affect what I am working on, so feel free to take care of > > > it whenever it fits your schedule. > > > > Good catch, thank you! > > > > It looks like the first two hunks in include/linux/srcu.h from that > > later commit need to be in that earlier commit. > > > > Frederic, does this make sense, or am I off in the weeds? > > Actually you need to do that earlier, in > 6584822b1be1 ("srcu: Create an srcu_read_lock_nmisafe() and srcu_read_unlock_nmisafe()") > > This way you don't only fix x86 bisectability but also the one of all the other safe archs. > > And it's not just the first two hunks, you also need to include > the removal of the srcutiny.h/srcutree.h definitions. > > So namely you need to apply the following to 6584822b1be1. You might > meet some minor retro-conflicts (the chknmisafe parameter didn't exist yet), > but that's pretty much it: Thank you both! I have an untested but allegedly fixed branch on -rcu on branch srcunmisafe.2022.10.20a. Thanx, Paul > diff --git a/include/linux/srcu.h b/include/linux/srcu.h > index 565f60d57484..f0814ffca34b 100644 > --- a/include/linux/srcu.h > +++ b/include/linux/srcu.h > @@ -52,8 +52,6 @@ int init_srcu_struct(struct srcu_struct *ssp); > #else > /* Dummy definition for things like notifiers. Actual use gets link error. */ > struct srcu_struct { }; > -int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe) __acquires(ssp); > -void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe) __releases(ssp); > #endif > > void call_srcu(struct srcu_struct *ssp, struct rcu_head *head, > @@ -66,6 +64,20 @@ unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp); > unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp); > bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie); > > +#ifdef CONFIG_NEED_SRCU_NMI_SAFE > +int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquires(ssp); > +void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) __releases(ssp); > +#else > +static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp) > +{ > + return __srcu_read_lock(ssp); > +} > +static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx) > +{ > + __srcu_read_unlock(ssp, idx); > +} > +#endif /* CONFIG_NEED_SRCU_NMI_SAFE */ > + > #ifdef CONFIG_SRCU > void srcu_init(void); > #else /* #ifdef CONFIG_SRCU */ > diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h > index f890301f123d..f3a4d65b91ef 100644 > --- a/include/linux/srcutiny.h > +++ b/include/linux/srcutiny.h > @@ -89,16 +89,4 @@ static inline void srcu_torture_stats_print(struct srcu_struct *ssp, > data_race(READ_ONCE(ssp->srcu_idx)), > data_race(READ_ONCE(ssp->srcu_idx_max))); > } > - > -static inline int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe) > -{ > - BUG(); > - return 0; > -} > - > -static inline void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe) > -{ > - BUG(); > -} > - > #endif > diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h > index 35ffdedf86cc..c689a81752c9 100644 > --- a/include/linux/srcutree.h > +++ b/include/linux/srcutree.h > @@ -159,7 +155,4 @@ void synchronize_srcu_expedited(struct srcu_struct *ssp); > void srcu_barrier(struct srcu_struct *ssp); > void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); > > -int __srcu_read_lock_nmisafe(struct srcu_struct *ssp, bool chknmisafe) __acquires(ssp); > -void __srcu_read_unlock_nmisafe(struct srcu_struct *ssp, int idx, bool chknmisafe) __releases(ssp); > - > #endif > >