From patchwork Tue Jul 13 16:19:06 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 12374459 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=-14.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MIME_BASE64_TEXT, SPF_HELO_NONE,SPF_PASS 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 4709DC11F6C for ; Tue, 13 Jul 2021 16:19:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3372561249 for ; Tue, 13 Jul 2021 16:19:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231406AbhGMQWP (ORCPT ); Tue, 13 Jul 2021 12:22:15 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:40413 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231451AbhGMQWN (ORCPT ); Tue, 13 Jul 2021 12:22:13 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626193162; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=LkVbvILKBq40WaEmHLBRSgoHvH/vzwrA0dUxLC2cHSE=; b=h4NVAU573xF6cAzB8SuI9BaVEwASb+RKGKVCOETmsdML3QHe8s8FsGt4NzHrPAskGWAbK7 p8fBOY2ENmIXGh5LXEcHR3/Q2pQMNUxblg7UTRMj7xtCFTVlBsLWoZisZtYS98kQVPOoDu vG0qD+imlrDNaM7bcGWu3/VDOcl8h7E= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-522-kWE6OaooNECjV1bN-9szzQ-1; Tue, 13 Jul 2021 12:19:21 -0400 X-MC-Unique: kWE6OaooNECjV1bN-9szzQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CF48C1009444; Tue, 13 Jul 2021 16:19:19 +0000 (UTC) Received: from localhost (ovpn-112-172.ams2.redhat.com [10.36.112.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 713906091B; Tue, 13 Jul 2021 16:19:19 +0000 (UTC) From: Stefan Hajnoczi To: linux-kernel@vger.kernel.org Cc: Daniel Lezcano , Stefano Garzarella , Ming Lei , "Michael S . Tsirkin" , Marcelo Tosatti , Jens Axboe , Jason Wang , linux-block@vger.kernel.org, "Rafael J. Wysocki" , virtualization@lists.linux-foundation.org, linux-pm@vger.kernel.org, Christoph Hellwig , Stefan Hajnoczi Subject: [RFC 3/3] softirq: participate in cpuidle polling Date: Tue, 13 Jul 2021 17:19:06 +0100 Message-Id: <20210713161906.457857-4-stefanha@redhat.com> In-Reply-To: <20210713161906.457857-1-stefanha@redhat.com> References: <20210713161906.457857-1-stefanha@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Normally softirqs are invoked when exiting irqs. When polling in the cpuidle driver there may be no irq. Therefore pending softirqs go unnoticed and polling continues without invoking them. Add a softirq_poll() function to explicitly check for and invoke softirqs. Signed-off-by: Stefan Hajnoczi --- This commit is not needed for virtio-blk. I added it when I realized virtio-net's NAPI scheduling might not be detected by the cpuidle busy wait loop because it is unaware of softirqs. However, even after doing this virtio-net's NAPI polling doesn't combine with cpuidle haltpoll. Perhaps this patch is still desirable for cpuidle poll_state in case a softirq is raised? --- include/linux/interrupt.h | 2 ++ drivers/cpuidle/poll_source.c | 3 +++ kernel/softirq.c | 14 ++++++++++++++ 3 files changed, 19 insertions(+) diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h index 4777850a6dc7..9bfdcc466ba8 100644 --- a/include/linux/interrupt.h +++ b/include/linux/interrupt.h @@ -573,6 +573,8 @@ struct softirq_action asmlinkage void do_softirq(void); asmlinkage void __do_softirq(void); +extern void softirq_poll(void); + extern void open_softirq(int nr, void (*action)(struct softirq_action *)); extern void softirq_init(void); extern void __raise_softirq_irqoff(unsigned int nr); diff --git a/drivers/cpuidle/poll_source.c b/drivers/cpuidle/poll_source.c index 46100e5a71e4..ed200feb0daa 100644 --- a/drivers/cpuidle/poll_source.c +++ b/drivers/cpuidle/poll_source.c @@ -6,6 +6,7 @@ #include #include #include +#include /* The per-cpu list of registered poll sources */ DEFINE_PER_CPU(struct list_head, poll_source_list); @@ -26,6 +27,8 @@ void poll_source_run_once(void) list_for_each_entry(src, this_cpu_ptr(&poll_source_list), node) src->ops->poll(src); + + softirq_poll(); } /* Called from idle task with TIF_POLLING_NRFLAG set and irqs enabled */ diff --git a/kernel/softirq.c b/kernel/softirq.c index 4992853ef53d..f45bf0204218 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -611,6 +611,20 @@ void irq_enter(void) irq_enter_rcu(); } +/** + * softirq_poll() - invoke pending softirqs + * + * Normally it is not necessary to explicitly poll for softirqs, but in the + * cpuidle driver a polling function may have raised a softirq with no irq exit + * to invoke it. Therefore it is necessary to poll for pending softirqs and + * invoke them explicitly. + */ +void softirq_poll(void) +{ + if (!in_interrupt() && local_softirq_pending()) + invoke_softirq(); +} + static inline void tick_irq_exit(void) { #ifdef CONFIG_NO_HZ_COMMON