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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 A5025CA90AF for ; Tue, 12 May 2020 16:13:38 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 794C3206B7 for ; Tue, 12 May 2020 16:13:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 794C3206B7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=proxmox.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58160 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jYXXF-0001PY-IC for qemu-devel@archiver.kernel.org; Tue, 12 May 2020 12:13:37 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:45784) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jYXWH-0000kl-BD; Tue, 12 May 2020 12:12:37 -0400 Received: from proxmox-new.maurer-it.com ([212.186.127.180]:8521) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jYXWE-00067s-L1; Tue, 12 May 2020 12:12:36 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id EFA7442D8B; Tue, 12 May 2020 18:03:03 +0200 (CEST) Subject: Re: [RFC PATCH 2/3] block: Allow bdrv_run_co() from different AioContext To: Kevin Wolf , qemu-block@nongnu.org References: <20200512144318.181049-1-kwolf@redhat.com> <20200512144318.181049-3-kwolf@redhat.com> From: Thomas Lamprecht Message-ID: <47293da5-b5e5-e61f-753d-4d16712f6d12@proxmox.com> Date: Tue, 12 May 2020 18:02:58 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:77.0) Gecko/20100101 Thunderbird/77.0 MIME-Version: 1.0 In-Reply-To: <20200512144318.181049-3-kwolf@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=212.186.127.180; envelope-from=t.lamprecht@proxmox.com; helo=proxmox-new.maurer-it.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/12 12:03:05 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, s.reiter@proxmox.com, armbru@redhat.com, stefanha@redhat.com, mreitz@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/12/20 4:43 PM, Kevin Wolf wrote: > Coroutine functions that are entered through bdrv_run_co() are already > safe to call from synchronous code in a different AioContext because > bdrv_coroutine_enter() will schedule them in the context of the node. > > However, the coroutine fastpath still requires that we're already in the > right AioContext when called in coroutine context. > > In order to make the behaviour more consistent and to make life a bit > easier for callers, let's check the AioContext and automatically move > the current coroutine around if we're not in the right context yet. > > Signed-off-by: Kevin Wolf > --- > block/io.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/block/io.c b/block/io.c > index c1badaadc9..7808e8bdc0 100644 > --- a/block/io.c > +++ b/block/io.c > @@ -895,8 +895,21 @@ static int bdrv_run_co(BlockDriverState *bs, CoroutineEntry *entry, > void *opaque, int *ret) > { > if (qemu_in_coroutine()) { > - /* Fast-path if already in coroutine context */ > + Coroutine *self = qemu_coroutine_self(); > + AioContext *bs_ctx = bdrv_get_aio_context(bs); > + AioContext *co_ctx = qemu_coroutine_get_aio_context(self); > + > + if (bs_ctx != co_ctx) { > + /* Move to the iothread of the node */ > + aio_co_schedule(bs_ctx, self); > + qemu_coroutine_yield(); > + } > entry(opaque); > + if (bs_ctx != co_ctx) { > + /* Move back to the original AioContext */ > + aio_co_schedule(bs_ctx, self); shouldn't it use co_ctx here, as else it's just scheduled again on the one from bs? Looks OK for me besides that. > + qemu_coroutine_yield(); > + } > } else { > Coroutine *co = qemu_coroutine_create(entry, opaque); > *ret = NOT_DONE; >