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 70462C4332F for ; Thu, 20 Oct 2022 22:42:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229868AbiJTWmF (ORCPT ); Thu, 20 Oct 2022 18:42:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229779AbiJTWmC (ORCPT ); Thu, 20 Oct 2022 18:42:02 -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 00DCF222F32; Thu, 20 Oct 2022 15:41:49 -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 C613FB8224C; Thu, 20 Oct 2022 22:41:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 69FBDC433D6; Thu, 20 Oct 2022 22:41:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666305706; bh=Yi4fDwSopn4pkowl2P2tTxm/UJWI6VaP5ZfVWNtQKvM=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=gpAMmahO3E4acOm9gJLrL+b9ScxKrlfJraDV6LtILX0BSz9nKft5lmvO7XuLB3Pp9 8vlJqa3lT4ZtCDDpQc1HtmZ5XY1+XSkuxkGDSJ3P/II05+vlyvjqCxAnmD6hYaNtBO LeP26d68XGpwpddeC+k3+SWNyyOPsgkcLMYA0DcuWX2fEZgDp8kT8W34rnocsfXziU 9fM4GKb9bBArzsxwFjwets/PLxQFhs/Xc6V5QpHt2I5wS8crMQ8+Yy26OJVUBFAyeX GHXT71fu7fCSqrmUWZKBLRhfPz6ySeRW/wM+5thGosFBvdWmnA+922b3+EzpZqiUuQ 7pzxmFBAXCZhA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 0BC1E5C1109; Thu, 20 Oct 2022 15:41:46 -0700 (PDT) Date: Thu, 20 Oct 2022 15:41:46 -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: <20221020224146.GA354603@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <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> <20221020222718.GA5600@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221020222718.GA5600@paulmck-ThinkPad-P17-Gen-1> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 20, 2022 at 03:27:18PM -0700, Paul E. McKenney wrote: > 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. Aside from having accidentally fused Frederic's last two commits together. I will split them back out on the next rebase. 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 > > > >