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spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46720 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l3zZe-0008G9-E0 for qemu-devel@archiver.kernel.org; Mon, 25 Jan 2021 05:58:22 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57810) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l3zZ2-0007lT-MS for qemu-devel@nongnu.org; Mon, 25 Jan 2021 05:57:44 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:60398) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l3zZ0-00024D-9h for qemu-devel@nongnu.org; Mon, 25 Jan 2021 05:57:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611572259; 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=n92av1VO1pDJTB6mFQmlWppnyyAW3a82s2Cj8HujAYs=; b=dj6ss/KoE+OLlrGy4fwimFTWeSO57iAKtk+KuUsvD/zoetwGmfL//B2nnsY1vwMZulsBI0 a5djZGhLVH+eSpsbcm4Aeo+nP8RVqVxm+oGQAzEF3OE3DFpqpEQsIIYWY97dOKVzKf1GD6 ZT16jmXYrzZzLK/PisRFlnVdSZCpcb8= 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-549-qOKCjfZcMiC80D2iSHklAA-1; Mon, 25 Jan 2021 05:57:38 -0500 X-MC-Unique: qOKCjfZcMiC80D2iSHklAA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E3C54100C600; Mon, 25 Jan 2021 10:57:36 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-114-237.ams2.redhat.com [10.36.114.237]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4DE1E71D58; Mon, 25 Jan 2021 10:57:31 +0000 (UTC) Subject: Re: [PATCH] coroutine-sigaltstack: Keep SIGUSR2 handler up To: Laszlo Ersek , qemu-devel@nongnu.org References: <20210122102041.27031-1-mreitz@redhat.com> <1121a803-98e7-6d41-119c-3d82717976ec@redhat.com> <95b1fd67-e980-be70-addc-6f1ac5f95f3d@redhat.com> From: Max Reitz Message-ID: <3cfa7f82-866b-e8b7-3e61-bb3dedff3226@redhat.com> Date: Mon, 25 Jan 2021 11:57:29 +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: <95b1fd67-e980-be70-addc-6f1ac5f95f3d@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 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: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.25, 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=-0.01, RCVD_IN_MSPIKE_WL=-0.01, 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 , Peter Maydell , =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= , Markus Armbruster , Stefan Hajnoczi , Paolo Bonzini Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 23.01.21 01:41, Laszlo Ersek wrote: > On 01/22/21 22:26, Laszlo Ersek wrote: > >> I'm drifting towards an overhaul of coroutine-sigaltstack, based on my >> personal understanding of POSIX, but given that I can absolutely not >> *test* coroutine-sigaltstack on the platforms where it actually matters, >> an "overhaul" by me would be reckless. >> >> I didn't expect these skeletons when I first read Max's "Thread safety >> of coroutine-sigaltstack" email :/ >> >> Max, after having worked on top of your patch for a few hours, I >> officially endorse your mutex approach. I can't encourage you or myself >> to touch this code, in good conscience. It's not that it's "bad"; it's >> inexplicable and (to me) untestable. On one hand, that’s too bad; on the other perhaps it’s just for the better to get all of this out of our minds again (for now)... O:) > I'm attaching a patch (based on 0e3246263068). I'm not convinced that I > should take responsibility for this, given the lack of testability on my > end. So I'm not posting it stand-alone even as an RFC. I've built it and > have booted one of my existent domains with it, but that's all. FWIW, it looks good to me. We should keep it in mind if in the future for some reason sigaltstack becomes more important, but for now I’m not too sad to abort any improvement efforts. Max