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 91B7BC4332F for ; Mon, 11 Dec 2023 20:04:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344920AbjLKUED (ORCPT ); Mon, 11 Dec 2023 15:04:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229790AbjLKUEB (ORCPT ); Mon, 11 Dec 2023 15:04:01 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 496B2D8 for ; Mon, 11 Dec 2023 12:04:08 -0800 (PST) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 71CFDC433C7; Mon, 11 Dec 2023 20:04:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1702325047; bh=CB/ZILfzWkqt0zgGJLAEBpldUB3+zyNpoonT0GRnSAc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=g3LoFel/RjaKrbKg7l7rU7wbifetCkYO+bcMXGxYp2tCcOP6+Un2Uv2NG9kNNqjOC 2KLartpPxHgz9YX2hct8ORM0z64paFHwEN4JF+8Yhnynt0/PQtWQpEhqaHq3nqEu5A R7oTFH3hZeBkVbDcgQ0g2tlqyqm3inbjP8MGE5FB0IQ4zMiQ3Btip/Bp9lqxwSnSKz MbSsczCe5HJDHzugjfTTArg/5+szlNFSjFUo9k37Y3XXDxVwxiivYW3+ZUhpQRw8JO jJmsil+9/v8W+qjEKNE+LDLQzxvVlQF/VWhWMW4SbBWX8ctYw90jNFyY1oh3rqt7DV /jUd5MPrw00Iw== Date: Mon, 11 Dec 2023 21:04:04 +0100 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: LKML , Boqun Feng , Joel Fernandes , Neeraj Upadhyay , Uladzislau Rezki , Zqiang , rcu Subject: Re: [PATCH 0/8] rcu: Fix expedited GP deadlock (and cleanup some nocb stuff) Message-ID: References: <20231208220545.7452-1-frederic@kernel.org> <0be847d6-804e-4f9d-9eb4-beee9efb6c78@paulmck-laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0be847d6-804e-4f9d-9eb4-beee9efb6c78@paulmck-laptop> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le Mon, Dec 11, 2023 at 08:38:59AM -0800, Paul E. McKenney a écrit : > On Fri, Dec 08, 2023 at 11:05:37PM +0100, Frederic Weisbecker wrote: > > TREE04 can trigger a writer stall if run with memory pressure. This > > is due to a circular dependency between waiting for expedited grace > > period and polling on expedited grace period when workqueues go back > > to mayday serialization. > > > > Here is a proposal fix. > > The torture.sh "acceptance test" with KCSAN and --duration 30 ran > fine except for this in TREE09: > > kernel/rcu/tree_nocb.h:1785:13: error: unused function '__call_rcu_nocb_wake' [-Werror,-Wunused-function] > > My guess is that the declaration of __call_rcu_nocb_wake() in > kernel/rcu/tree.h needs an "#ifdef CONFIG_SMP", but you might have a > better fix. Could be because if CONFIG_RCU_NO_CB_CPU=n, the function is only called (though as dead code) from rcutree_migrate_callbacks() which in turn only exists if CONFIG_HOTPLUG_CPU=y. Something like that then: diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 35f7af331e6c..e1ff53d5084c 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -445,6 +445,8 @@ static void rcu_qs(void); static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); #ifdef CONFIG_HOTPLUG_CPU static bool rcu_preempt_has_tasks(struct rcu_node *rnp); +static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, + unsigned long flags); #endif /* #ifdef CONFIG_HOTPLUG_CPU */ static int rcu_print_task_exp_stall(struct rcu_node *rnp); static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp); @@ -466,8 +468,6 @@ static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp, unsigned long j, bool lazy); static void call_rcu_nocb(struct rcu_data *rdp, struct rcu_head *head, rcu_callback_t func, unsigned long flags, bool lazy); -static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty, - unsigned long flags); static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level); static bool do_nocb_deferred_wakeup(struct rcu_data *rdp); static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);