From patchwork Mon Feb 10 12:32:29 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 232030 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 165EAC352A4 for ; Mon, 10 Feb 2020 12:36:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E1B182465D for ; Mon, 10 Feb 2020 12:36:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338162; bh=ybAVDw8a+2yH1pyo9WP0iudYGr9/9Kh4ncRyyYMBtb8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=VMyv13JoEyLZ1UxjnH3l/43iP468upUendznA/fJ+2mUhUHTEyU2LETtquSLS8lwh tME9EgA7hSBwhzd0Gmcov21ZB267R+jyLoyNN1PHN8vBJyUFTQzTJcJN8zFKT3WH6U QIFoEOZHpG+JnTORCJ6H1arudexci1rIxsnkW6dk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728215AbgBJMgC (ORCPT ); Mon, 10 Feb 2020 07:36:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:54426 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728204AbgBJMgA (ORCPT ); Mon, 10 Feb 2020 07:36:00 -0500 Received: from localhost (unknown [209.37.97.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D745E20838; Mon, 10 Feb 2020 12:35:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338159; bh=ybAVDw8a+2yH1pyo9WP0iudYGr9/9Kh4ncRyyYMBtb8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VdzZVNiFxtFMCIVC0fnsCDAGkNjAZQ3Ep1eCM4+/sUY20M2Dhofhbq9s6hNBmmFxC meLKcDo5fyOUNk0GxdDy6CtVlJszocxZpUZUCygzPpvq2WquvBKGTEfUdBQCaMj9a9 m2TOcEuLP65t0WaFAxt5s+Tt5PirPl3x7A97xAgs= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Herbert Xu , Daniel Jordan , Sasha Levin Subject: [PATCH 4.19 091/195] padata: Remove broken queue flushing Date: Mon, 10 Feb 2020 04:32:29 -0800 Message-Id: <20200210122314.217904406@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200210122305.731206734@linuxfoundation.org> References: <20200210122305.731206734@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Herbert Xu [ Upstream commit 07928d9bfc81640bab36f5190e8725894d93b659 ] The function padata_flush_queues is fundamentally broken because it cannot force padata users to complete the request that is underway. IOW padata has to passively wait for the completion of any outstanding work. As it stands flushing is used in two places. Its use in padata_stop is simply unnecessary because nothing depends on the queues to be flushed afterwards. The other use in padata_replace is more substantial as we depend on it to free the old pd structure. This patch instead uses the pd->refcnt to dynamically free the pd structure once all requests are complete. Fixes: 2b73b07ab8a4 ("padata: Flush the padata queues actively") Cc: Signed-off-by: Herbert Xu Reviewed-by: Daniel Jordan Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- kernel/padata.c | 46 ++++++++++++---------------------------------- 1 file changed, 12 insertions(+), 34 deletions(-) diff --git a/kernel/padata.c b/kernel/padata.c index 6c06b3039faed..11c5f9c8779ea 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -35,6 +35,8 @@ #define MAX_OBJ_NUM 1000 +static void padata_free_pd(struct parallel_data *pd); + static int padata_index_to_cpu(struct parallel_data *pd, int cpu_index) { int cpu, target_cpu; @@ -334,6 +336,7 @@ static void padata_serial_worker(struct work_struct *serial_work) struct padata_serial_queue *squeue; struct parallel_data *pd; LIST_HEAD(local_list); + int cnt; local_bh_disable(); squeue = container_of(serial_work, struct padata_serial_queue, work); @@ -343,6 +346,8 @@ static void padata_serial_worker(struct work_struct *serial_work) list_replace_init(&squeue->serial.list, &local_list); spin_unlock(&squeue->serial.lock); + cnt = 0; + while (!list_empty(&local_list)) { struct padata_priv *padata; @@ -352,9 +357,12 @@ static void padata_serial_worker(struct work_struct *serial_work) list_del_init(&padata->list); padata->serial(padata); - atomic_dec(&pd->refcnt); + cnt++; } local_bh_enable(); + + if (atomic_sub_and_test(cnt, &pd->refcnt)) + padata_free_pd(pd); } /** @@ -501,8 +509,7 @@ static struct parallel_data *padata_alloc_pd(struct padata_instance *pinst, timer_setup(&pd->timer, padata_reorder_timer, 0); atomic_set(&pd->seq_nr, -1); atomic_set(&pd->reorder_objects, 0); - atomic_set(&pd->refcnt, 0); - pd->pinst = pinst; + atomic_set(&pd->refcnt, 1); spin_lock_init(&pd->lock); return pd; @@ -526,31 +533,6 @@ static void padata_free_pd(struct parallel_data *pd) kfree(pd); } -/* Flush all objects out of the padata queues. */ -static void padata_flush_queues(struct parallel_data *pd) -{ - int cpu; - struct padata_parallel_queue *pqueue; - struct padata_serial_queue *squeue; - - for_each_cpu(cpu, pd->cpumask.pcpu) { - pqueue = per_cpu_ptr(pd->pqueue, cpu); - flush_work(&pqueue->work); - } - - del_timer_sync(&pd->timer); - - if (atomic_read(&pd->reorder_objects)) - padata_reorder(pd); - - for_each_cpu(cpu, pd->cpumask.cbcpu) { - squeue = per_cpu_ptr(pd->squeue, cpu); - flush_work(&squeue->work); - } - - BUG_ON(atomic_read(&pd->refcnt) != 0); -} - static void __padata_start(struct padata_instance *pinst) { pinst->flags |= PADATA_INIT; @@ -564,10 +546,6 @@ static void __padata_stop(struct padata_instance *pinst) pinst->flags &= ~PADATA_INIT; synchronize_rcu(); - - get_online_cpus(); - padata_flush_queues(pinst->pd); - put_online_cpus(); } /* Replace the internal control structure with a new one. */ @@ -588,8 +566,8 @@ static void padata_replace(struct padata_instance *pinst, if (!cpumask_equal(pd_old->cpumask.cbcpu, pd_new->cpumask.cbcpu)) notification_mask |= PADATA_CPU_SERIAL; - padata_flush_queues(pd_old); - padata_free_pd(pd_old); + if (atomic_dec_and_test(&pd_old->refcnt)) + padata_free_pd(pd_old); if (notification_mask) blocking_notifier_call_chain(&pinst->cpumask_change_notifier,