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 7A9B3C433F5 for ; Tue, 8 Feb 2022 15:16:44 +0000 (UTC) Received: from localhost ([::1]:48232 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nHSEV-0008II-7a for qemu-devel@archiver.kernel.org; Tue, 08 Feb 2022 10:16:43 -0500 Received: from eggs.gnu.org ([209.51.188.92]:57204) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHQEq-0004pR-OV for qemu-devel@nongnu.org; Tue, 08 Feb 2022 08:09:00 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:40875) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nHQEm-0000Z2-3R for qemu-devel@nongnu.org; Tue, 08 Feb 2022 08:08:53 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1644325729; 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=3ABLpRQN5miU1fDjcMJCf3vM/oOO/3WZwgiJQGz9q+Y=; b=jLm3CS9wddj/grVKzr1wHigwBx++leay7GAZkcTCPLoHMvEYODh3Fd/nne0+Qo6S0R+ZeJ fT3sk/3onrJ6CeHrFWyndXiFp0oHgvM6695ha83npeEwd5OKRtJNaeMNGCYWV3nSJhTcPA Fo/ELuH5T6DfB+4Yfds+q/hjHsgIro8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-1-0ZUm7QZ6NreEJqP6in3szw-1; Tue, 08 Feb 2022 08:08:42 -0500 X-MC-Unique: 0ZUm7QZ6NreEJqP6in3szw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 758BD85EE62; Tue, 8 Feb 2022 13:08:39 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.242]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6A1776E214; Tue, 8 Feb 2022 13:08:13 +0000 (UTC) Date: Tue, 8 Feb 2022 14:08:12 +0100 From: Kevin Wolf To: Emanuele Giuseppe Esposito Subject: Re: [PATCH v6 00/33] block layer: split block APIs in global state and I/O Message-ID: References: <20220121170544.2049944-1-eesposit@redhat.com> <1f3d2562-c355-4295-77b5-088d2ed49023@redhat.com> MIME-Version: 1.0 In-Reply-To: <1f3d2562-c355-4295-77b5-088d2ed49023@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable 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: , Cc: Fam Zheng , qemu-devel@nongnu.org, "Denis V. Lunev" , Eric Blake , qemu-block@nongnu.org, Juan Quintela , Daniel Henrique Barboza , Markus Armbruster , Richard Henderson , Greg Kurz , "Dr. David Alan Gilbert" , =?iso-8859-1?Q?C=E9dric?= Le Goater , Stefan Hajnoczi , John Snow , David Gibson , Eduardo Habkost , Vladimir Sementsov-Ogievskiy , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Hanna Reitz , qemu-ppc@nongnu.org, Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 08.02.2022 um 12:42 hat Emanuele Giuseppe Esposito geschrieben: > > > On 07/02/2022 19:30, Kevin Wolf wrote: > > Am 21.01.2022 um 18:05 hat Emanuele Giuseppe Esposito geschrieben: > >> Each function in the GS API will have an assertion, checking > >> that it is always running under BQL. > >> I/O functions are instead thread safe (or so should be), meaning > >> that they *can* run under BQL, but also in an iothread in another > >> AioContext. Therefore they do not provide any assertion, and > >> need to be audited manually to verify the correctness. > > > > I wonder if we could actually do something to catch at least some kinds > > of bugs. The first conclusion from thinking about it is that we probably > > shouldn't open-code assert(qemu_in_main_thread()) everywhere, but have a > > macro or inline function for each category to be called in each function. > > > > So an IO_CODE() macro could increase a counter in the coroutine object > > (that is decreased again at the end of the function with g_auto), and > > then GLOBAL_STATE_CODE() could not only assert that we're holding the > > BQL, but also that the counter is still 0, i.e. it is not (indirectly) > > called by an I/O function. > > > > We may want to enable this only in debug builds, but maybe still worth a > > thought anyway? > > I don't understand what is the point of the counter, do you want to use > it as a boolean flag? It would only be checked as a boolean flag, but it needs to be a counter because of nesting where e.g. one I/O function calls another I/O function. > Would a single counter work in a multi-threaded context? Shouldn't we > have it per-thread? And why you increase it only in coroutines? I don't mean increasing it only in coroutine context, but having a per-coroutine counter, including the leader coroutine which exists for non-coroutine context in every thread. Kevin