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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 87EE2C2BB85 for ; Thu, 16 Apr 2020 10:10:34 +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 593D721D81 for ; Thu, 16 Apr 2020 10:10:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 593D721D81 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]:60286 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jP1Td-0000Ex-F2 for qemu-devel@archiver.kernel.org; Thu, 16 Apr 2020 06:10:33 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:60537) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jP1Sp-0007vt-4l for qemu-devel@nongnu.org; Thu, 16 Apr 2020 06:09:43 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jP1So-0005EY-78 for qemu-devel@nongnu.org; Thu, 16 Apr 2020 06:09:42 -0400 Received: from proxmox-new.maurer-it.com ([212.186.127.180]:39951) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jP1So-0005Do-0K for qemu-devel@nongnu.org; Thu, 16 Apr 2020 06:09:42 -0400 Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 21773420BF; Thu, 16 Apr 2020 12:09:36 +0200 (CEST) Date: Thu, 16 Apr 2020 12:09:34 +0200 (CEST) From: Dietmar Maurer To: Kevin Wolf , Stefan Reiter Message-ID: <1548825935.27.1587031774908@webmail.proxmox.com> In-Reply-To: <20200416082849.GA6014@linux.fritz.box> References: <5dde1955-49db-2626-1fa5-332e4d7a0928@proxmox.com> <20200416082849.GA6014@linux.fritz.box> Subject: Re: qemu_coroutine_yield switches thread? MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Priority: 3 Importance: Normal X-Mailer: Open-Xchange Mailer v7.10.2-Rev25 X-Originating-Client: open-xchange-appsuite X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 212.186.127.180 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: , Reply-To: Dietmar Maurer Cc: vsementsov@virtuozzo.com, slp@redhat.com, "qemu-devel@nongnu.org" , mreitz@redhat.com, stefanha@redhat.com, jsnow@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" > > quick question: Can a resume from a qemu_coroutine_yield happen in a > > different thread? > > > > Well, it can, since I'm seeing it happen, but is that okay or a bug? > > Yes, it can happen. At least for devices like IDE where a request is > started during a vmexit (MMIO or I/O port write), the coroutine will > usually begin its life in the vcpu thread and then move to the main loop > thread. > > This is not a problem because the vcpu thread holds the BQL while > running the request coroutine. Isn't that a problem when using QemuRecMutex, for example: qemu_rec_mutex_lock(lock) ... qemu_coroutine_yield() // wait for something // we are now inside a different thread qemu_rec_mutex_unlock(lock) // Crash - wrong thread!! ?