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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 0F8E3C4828F for ; Wed, 7 Feb 2024 07:05:29 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1rXbzK-0004IH-2n; Wed, 07 Feb 2024 02:04:55 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rXbzA-0004HW-63 for qemu-devel@nongnu.org; Wed, 07 Feb 2024 02:04:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1rXbz8-0000o1-RX for qemu-devel@nongnu.org; Wed, 07 Feb 2024 02:04:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1707289481; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=KZHZyIRQUKWb/AUCDgSuBY1Pt7166CMJ+tHeNoSYCG0=; b=LCdzOu5OqUENFk+vguRMTFFyVyi2dLMCVbQdacjsVx1zftkoe9gWvPFFRV2dgfera2VY+C CehAWrQ0nAp3OQGlBFJPuU6CWMR1Payc+DwsIS6uyEygmGBnXf7NfNn6LVhVC0pLgX/txZ S51D/OWIUwCXkCsXp9NmmWcZvCpvvb8= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-9-UognUprrOn6wSid2w_752g-1; Wed, 07 Feb 2024 02:04:37 -0500 X-MC-Unique: UognUprrOn6wSid2w_752g-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8C5E129ABA23; Wed, 7 Feb 2024 07:04:37 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.123]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 56A58C1D36C; Wed, 7 Feb 2024 07:04:37 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 4EFFA21E66D0; Wed, 7 Feb 2024 08:04:36 +0100 (CET) From: Markus Armbruster To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, Kevin Wolf , Hanna Reitz , "Michael S. Tsirkin" , Michael Roth , qemu-block@nongnu.org Subject: Re: [PATCH 5/5] monitor: use aio_co_reschedule_self() In-Reply-To: <20240205172659.476970-6-stefanha@redhat.com> (Stefan Hajnoczi's message of "Mon, 5 Feb 2024 12:26:59 -0500") References: <20240205172659.476970-1-stefanha@redhat.com> <20240205172659.476970-6-stefanha@redhat.com> Date: Wed, 07 Feb 2024 08:04:36 +0100 Message-ID: <87v870n4aj.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.129.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.294, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Stefan Hajnoczi writes: > The aio_co_reschedule_self() API is designed to avoid the race > condition between scheduling the coroutine in another AioContext and > yielding. > > The QMP dispatch code uses the open-coded version that appears > susceptible to the race condition at first glance: > > aio_co_schedule(qemu_get_aio_context(), qemu_coroutine_self()); > qemu_coroutine_yield(); > > The code is actually safe because the iohandler and qemu_aio_context > AioContext run under the Big QEMU Lock. Nevertheless, set a good example > and use aio_co_reschedule_self() so it's obvious that there is no race. > > Suggested-by: Hanna Reitz > Signed-off-by: Stefan Hajnoczi Acked-by: Markus Armbruster Feel free to merge this together with the remainder of the series.