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 8F590C433EF for ; Tue, 19 Apr 2022 00:04:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237452AbiDSAHH (ORCPT ); Mon, 18 Apr 2022 20:07:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52794 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236959AbiDSAGJ (ORCPT ); Mon, 18 Apr 2022 20:06:09 -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 997C729811; Mon, 18 Apr 2022 17:03:28 -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 2124AB81147; Tue, 19 Apr 2022 00:03:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 10929C385BB; Tue, 19 Apr 2022 00:03:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650326605; bh=lyjONtqSbnzzy2uBjKzwL8KfGkjOoSlgn7pyA+mj6/U=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Mkgdn4M5oB9OoSqAu55ZEyQz393wg6gC6DZAwCRubHlDFFbt87VBtGr8Vko7bWh4u Iui26/tjpkfUxiXQ+x5dt56JOjUN5+DoBVbxyH7TTp2+rwrmg30EiIDE4d/wqfnkyi ZPnYEwaDXU2QvosmHPtStrD4cp15M/624W+rdifuxnDuV3WgSMy283vrOS4xtiXL06 EZy+myupAat6x0JQHbB06wAanOWOUqVj8dnu5xD/za3V0xL/RtLp7vQMWoxIbpwvYb rkuA6hgP+VaGPTqsttKtSrFoXfE/vTxhw93j2+ueym18o18bM0lvpsXY/m1Ub/fZgM his/QY6is5SBw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 660AC5C2B13; Mon, 18 Apr 2022 17:03:24 -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" , Neeraj Upadhyay Subject: [PATCH rcu 14/21] srcu: Prevent cleanup_srcu_struct() from freeing non-dynamic ->sda Date: Mon, 18 Apr 2022 17:03:15 -0700 Message-Id: <20220419000322.3948903-14-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20220419000315.GA3948789@paulmck-ThinkPad-P17-Gen-1> References: <20220419000315.GA3948789@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 When an srcu_struct structure is created (but not in a kernel module) by DEFINE_SRCU() and friends, the per-CPU srcu_data structure is statically allocated. In all other cases, that structure is obtained from alloc_percpu(), in which case cleanup_srcu_struct() must invoke free_percpu() on the resulting ->sda pointer in the srcu_struct pointer. Which it does. Except that it also invokes free_percpu() on the ->sda pointer referencing the statically allocated per-CPU srcu_data structures. Which free_percpu() is surprisingly OK with. This commit nevertheless stops cleanup_srcu_struct() from freeing statically allocated per-CPU srcu_data structures. Co-developed-by: Neeraj Upadhyay Signed-off-by: Neeraj Upadhyay Signed-off-by: Paul E. McKenney --- include/linux/srcutree.h | 1 + kernel/rcu/srcutree.c | 9 ++++++--- 2 files changed, 7 insertions(+), 3 deletions(-) diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 44e998643f48..44bd204498a1 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -73,6 +73,7 @@ struct srcu_struct { unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */ unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */ struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */ + bool sda_is_static; /* May ->sda be passed to free_percpu()? */ unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */ struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */ struct completion srcu_barrier_completion; diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index b7138dbe1a2d..7209fd95dde9 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -217,6 +217,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) mutex_init(&ssp->srcu_barrier_mutex); atomic_set(&ssp->srcu_barrier_cpu_cnt, 0); INIT_DELAYED_WORK(&ssp->work, process_srcu); + ssp->sda_is_static = is_static; if (!is_static) ssp->sda = alloc_percpu(struct srcu_data); if (!ssp->sda) @@ -226,7 +227,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static) ssp->srcu_last_gp_end = ktime_get_mono_fast_ns(); if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && convert_to_big == 1) { if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) { - if (!is_static) { + if (!ssp->sda_is_static) { free_percpu(ssp->sda); ssp->sda = NULL; return -ENOMEM; @@ -446,8 +447,10 @@ void cleanup_srcu_struct(struct srcu_struct *ssp) rcu_seq_current(&ssp->srcu_gp_seq), ssp->srcu_gp_seq_needed); return; /* Caller forgot to stop doing call_srcu()? */ } - free_percpu(ssp->sda); - ssp->sda = NULL; + if (!ssp->sda_is_static) { + free_percpu(ssp->sda); + ssp->sda = NULL; + } kfree(ssp->node); ssp->node = NULL; ssp->srcu_size_state = SRCU_SIZE_SMALL; -- 2.31.1.189.g2e36527f23