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 F3FFCC433F5 for ; Tue, 19 Apr 2022 00:01:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236739AbiDSADk (ORCPT ); Mon, 18 Apr 2022 20:03:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236195AbiDSAC7 (ORCPT ); Mon, 18 Apr 2022 20:02:59 -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 8492B11145; Mon, 18 Apr 2022 17:00:19 -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 27747B81141; Tue, 19 Apr 2022 00:00:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94F09C385B7; Tue, 19 Apr 2022 00:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650326416; bh=4EFYBPM+fGUTWUUGcdM/Li8/8Rj9SLDD6se7yA60e4k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=J99x+TkUhjHDOZsEQ0dz7mFkh00X4WYXNS3ZJ6SD5xAMIOFF8DlJbaDR8N7xzy+7P RRhB6UUmJzwcWAO/0BqkWQw9CO6m5fCmW4EOFcMy0TC9AK9K+ZcxigVsQqicd4aLdn dY+shGly3v0HR7R4flST8Cpps60IA6ys1V2CLBG516vM8KtTVgOgJTJ2DT4eqxgjvV C4FZPbVgp027G20MH8VF0RiHkREB5IcZMIHGtseZ9ddKN/3ALnWmOvO133u0RP4U56 whDggywIOBgHlv1d+bA3EDTbd3Pn6pjcKXIZCP033DXcqx2MMcuIg37YHstBiiH0u3 AnV6hcqxRUajA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id E6AB25C12AB; Mon, 18 Apr 2022 17:00:15 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, rostedt@goodmis.org, "Paul E. McKenney" , Eric Dumazet Subject: [PATCH rcu 9/9] rcu-tasks: Handle sparse cpu_possible_mask in rcu_tasks_invoke_cbs() Date: Mon, 18 Apr 2022 17:00:14 -0700 Message-Id: <20220419000014.3948512-9-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220419000007.GA3945818@paulmck-ThinkPad-P17-Gen-1> References: <20220419000007.GA3945818@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If the cpu_possible_mask is sparse (for example, if bits are set only for CPUs 0, 4, 8, ...), then rcu_tasks_invoke_cbs() will access per-CPU data for a CPU not in cpu_possible_mask. It makes these accesses while doing a workqueue-based binary search for non-empty callback lists. Although this search must pass through CPUs not represented in cpu_possible_mask, it has no need to check the callback list for such CPUs. This commit therefore changes the rcu_tasks_invoke_cbs() function's binary search so as to only check callback lists for CPUs present in cpu_possible_mask. Reported-by: Eric Dumazet Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index fd70d86eb7cd..3925e32159b5 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -468,7 +468,7 @@ static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu } } - if (rcu_segcblist_empty(&rtpcp->cblist)) + if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu)) return; raw_spin_lock_irqsave_rcu_node(rtpcp, flags); rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq)); -- 2.31.1.189.g2e36527f23