From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:57190) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S4y54-0004QY-S1 for qemu-devel@nongnu.org; Tue, 06 Mar 2012 12:21:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1S4y4g-0002ZG-5c for qemu-devel@nongnu.org; Tue, 06 Mar 2012 12:21:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38941) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1S4y4f-0002Z8-Tt for qemu-devel@nongnu.org; Tue, 06 Mar 2012 12:21:22 -0500 Received: from int-mx02.intmail.prod.int.phx2.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id q26HLKTK032011 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Tue, 6 Mar 2012 12:21:20 -0500 Date: Tue, 6 Mar 2012 19:21:12 +0200 From: Alon Levy Message-ID: <20120306172112.GM2240@garlic.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [Qemu-devel] qxl screendump: how and why it is broken List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino , Gerd Hoffmann , Avi Kivity , qemu-devel@nongnu.org ..and why we got to this situation. (per Anthony's request, and if you'll excuse the puny attempt to write biblically, a new beginning) In the begining there was screendump. It was a synchronous monitor command. Libvirt said: I want a screendump. And qemu waited for the vga device to produce it. When the vga device said it was done, libvirt was done. Then there came qxl. Qxl used a spice library to render the contents. It would say to libvirt: wait, while I read on this thread, which will tell me I am done. And so it was possible to hang the libvirt process: tl;dr if spice client hangs libvirt screenshot hangs and qemu's vcpus starve. http://lists.gnu.org/archive/html/qemu-devel/2012-03/msg00864.html Then a new patchset landed, which stopped the read, by waiting for a callback from the spice server. It is here: http://patchwork.ozlabs.org/patch/142985/ commited as 81fb6f1504fb9ef71f2382f44af34756668296e8 But now screendump for qxl is broken: It produces a file that is old, because it calls ppm_save before spice server is done rendering. Now we come to now. My understanding from the previous thread is: * monitor async is not good because Luiz said so. (yes, I know I'm putting my head in the sand here) If the above is enough to convince you of $SUBJECT, then the screendump-async patchset is still waiting review :) http://patchwork.ozlabs.org/patch/144704/ http://patchwork.ozlabs.org/patch/144705/ http://patchwork.ozlabs.org/patch/144706/ Alon