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=-7.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 81CEBC433E0 for ; Fri, 22 Jan 2021 08:49:34 +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 BCC52235F9 for ; Fri, 22 Jan 2021 08:49:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BCC52235F9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:53212 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l2s8K-0002O3-II for qemu-devel@archiver.kernel.org; Fri, 22 Jan 2021 03:49:32 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:56924) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l2s78-0001ej-49 for qemu-devel@nongnu.org; Fri, 22 Jan 2021 03:48:18 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:42787) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l2s76-00031p-OE for qemu-devel@nongnu.org; Fri, 22 Jan 2021 03:48:17 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611305295; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1C3vvZ8pJShozVXJrN0lcwo0sgIbQkhM+4rXBecX5EE=; b=dxCp4Doyk50zcKhOfDHn/lk4YH/OALF5Vn7+BHRBKdi4CAJAZNdLzw32wsQTTJkrvFRwHa I9uzcoVdvUlAveKKiBkb6WVT2XEy3O8pOgSCBilN2tDllds2zHjvZxF2c/3vm7xWSSw+2K 2lh8EJrHxv/2VMrMAeQWMD+omRdW/GA= 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-319-HClW-OszO_-CcmKjgY0RCA-1; Fri, 22 Jan 2021 03:48:13 -0500 X-MC-Unique: HClW-OszO_-CcmKjgY0RCA-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 F22EE192D78A for ; Fri, 22 Jan 2021 08:48:12 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-114-109.ams2.redhat.com [10.36.114.109]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 103256EF40; Fri, 22 Jan 2021 08:48:09 +0000 (UTC) Subject: Re: Thread safety of coroutine-sigaltstack To: Laszlo Ersek , "qemu-devel@nongnu.org" References: <7b8155ad-0942-dc1c-f43c-bb5eb518a278@redhat.com> <445268c9-d91f-af5a-3d7e-f4c6f014ca52@redhat.com> From: Max Reitz Message-ID: Date: Fri, 22 Jan 2021 09:48:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <445268c9-d91f-af5a-3d7e-f4c6f014ca52@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mreitz@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=mreitz@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.168, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: Kevin Wolf , Stefan Hajnoczi Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 20.01.21 18:25, Laszlo Ersek wrote: [...] > A simple grep for SIGUSR2 seems to indicate that SIGUSR2 is not used by > system emulation for anything else, in practice. Is it possible to > dedicate SIGUSR2 explicitly to coroutine-sigaltstack, and set up the > action beforehand, from some init function that executes on a "central" > thread, before qemu_coroutine_new() is ever called? I wrote a patch to that effect, but just before sending I wondered whether SIGUSR2 cannot be registered by the “guest” in user-mode emulation, and whether that would then break coroutines from there on. (I have no experience dealing with user-mode emulation, but it does look like the guest can just register handlers for any signal but SIGSEGV and SIGBUS.) Max