From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:39136) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RgGPr-0007py-W0 for qemu-devel@nongnu.org; Thu, 29 Dec 2011 08:53:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RgGPq-0005aZ-PU for qemu-devel@nongnu.org; Thu, 29 Dec 2011 08:53:07 -0500 Received: from mx1.redhat.com ([209.132.183.28]:32514) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RgGPq-0005aP-Ge for qemu-devel@nongnu.org; Thu, 29 Dec 2011 08:53:06 -0500 Message-ID: <4EFC70BA.1080808@redhat.com> Date: Thu, 29 Dec 2011 15:52:58 +0200 From: Avi Kivity MIME-Version: 1.0 References: <4EFC4DF0.2040708@redhat.com> <20111229123922.GG19274@valinux.co.jp> <4EFC634E.10406@redhat.com> <20111229134920.GH19274@valinux.co.jp> In-Reply-To: <20111229134920.GH19274@valinux.co.jp> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 0/2][RFC] postcopy migration: Linux char device for postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Isaku Yamahata Cc: Andrea Arcangeli , t.hirofuchi@aist.go.jp, qemu-devel@nongnu.org, kvm@vger.kernel.org, satoshi.itoh@aist.go.jp On 12/29/2011 03:49 PM, Isaku Yamahata wrote: > > > > qemu can have an extra thread that wait4()s the daemon, and relaunch > > it. This extra thread would not be blocked by the page fault. It can > > keep the fd so it isn't lost. > > > > The unkillability of process A is a security issue; it could be done on > > purpose. Is it possible to change umem to sleep with > > TASK_INTERRUPTIBLE, so it can be killed? > > The issue is how to solve the page fault, not whether TASK_INTERRUPTIBLE or > TASK_UNINTERRUPTIBLE. > I can think of several options. > - When daemon X is dead, all page faults are served by zero pages. > - When daemon X is dead, all page faults are resovled as VM_FAULT_SIGBUS > - list/reattach: complications. You don't like it > - other? Don't resolve the page fault. It's up to the user/system to make sure it happens. qemu can easily do it by watching for the daemon's death and respawning it. When the new daemon is started, it can ask the kernel for a list of pending requests, and service them. -- error compiling committee.c: too many arguments to function