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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 911B7C3F357 for ; Thu, 27 Feb 2020 13:45:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 69036222C2 for ; Thu, 27 Feb 2020 13:45:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582811131; bh=K3Ra+BUQ5/jp2bDVeFTc3iJxPIsTfY1Xe7A0eQdM7K0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=vVTW0peU9ht3vWQn506MM/grDIrl+5dwTjUyAlBMALTNYuKdNV6snzSzLpB/bgMhb 9E7LU3NNbakXm68E+teN1dHzYgGJntTnNpgsVc/l0egA3umezyqnkcNeBVNoIagGE7 g/CBIIj5SJHCw0dlwXfrZSM3OqDNA0hOu36RX9Gc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730380AbgB0Npa (ORCPT ); Thu, 27 Feb 2020 08:45:30 -0500 Received: from mail.kernel.org ([198.145.29.99]:41342 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730361AbgB0Np0 (ORCPT ); Thu, 27 Feb 2020 08:45:26 -0500 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 472CE21D7E; Thu, 27 Feb 2020 13:45:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582811125; bh=K3Ra+BUQ5/jp2bDVeFTc3iJxPIsTfY1Xe7A0eQdM7K0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1fp4G6Qx9hVAJ/7akNmfwbfD8dsFph477ZVhwzS5RJD9pPNWBqd48QqEnuNYO3r4A fNVYa2VqdHYObeLxyBwKdxRp1BbPkTaLMy6JrF/n2weg0PbKzk/FLKuTZZVtorGc3y KiDjPevOlAAroTo73GRJ5VsH96UUtnWbG7rL6Q4A= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Herbert Xu , Daniel Jordan Subject: [PATCH 4.9 013/165] padata: Remove broken queue flushing Date: Thu, 27 Feb 2020 14:34:47 +0100 Message-Id: <20200227132232.980629716@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200227132230.840899170@linuxfoundation.org> References: <20200227132230.840899170@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Herbert Xu commit 07928d9bfc81640bab36f5190e8725894d93b659 upstream. 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 [dj: leave "pd->pinst = pinst" assignment in padata_alloc_pd()] Signed-off-by: Daniel Jordan Signed-off-by: Greg Kroah-Hartman --- kernel/padata.c | 45 ++++++++++++--------------------------------- 1 file changed, 12 insertions(+), 33 deletions(-) --- a/kernel/padata.c +++ b/kernel/padata.c @@ -34,6 +34,8 @@ #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; @@ -301,6 +303,7 @@ static void padata_serial_worker(struct 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); @@ -310,6 +313,8 @@ static void padata_serial_worker(struct list_replace_init(&squeue->serial.list, &local_list); spin_unlock(&squeue->serial.lock); + cnt = 0; + while (!list_empty(&local_list)) { struct padata_priv *padata; @@ -319,9 +324,12 @@ static void padata_serial_worker(struct 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); } /** @@ -444,7 +452,7 @@ static struct parallel_data *padata_allo setup_timer(&pd->timer, padata_reorder_timer, (unsigned long)pd); atomic_set(&pd->seq_nr, -1); atomic_set(&pd->reorder_objects, 0); - atomic_set(&pd->refcnt, 0); + atomic_set(&pd->refcnt, 1); pd->pinst = pinst; spin_lock_init(&pd->lock); @@ -469,31 +477,6 @@ static void padata_free_pd(struct parall 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; @@ -507,10 +490,6 @@ static void __padata_stop(struct padata_ 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. */ @@ -531,8 +510,8 @@ static void padata_replace(struct padata 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,