From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45875) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YNNcA-0002oe-5y for qemu-devel@nongnu.org; Mon, 16 Feb 2015 10:29:41 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YNNc4-0005bt-1O for qemu-devel@nongnu.org; Mon, 16 Feb 2015 10:29:38 -0500 Received: from mx1.redhat.com ([209.132.183.28]:34193) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YNNc3-0005bd-Q0 for qemu-devel@nongnu.org; Mon, 16 Feb 2015 10:29:31 -0500 Message-ID: <54E20CD5.3050909@redhat.com> Date: Mon, 16 Feb 2015 16:29:25 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <54AE87C1.2060907@wiesinger.com> <54AEBD43.2060705@redhat.com> <54AEC877.9080600@wiesinger.com> <54AECAF3.3060909@redhat.com> <54AF047D.8010009@wiesinger.com> <54B3B2F5.1090405@wiesinger.com> <54B57C51.7090002@wiesinger.com> <54B584AB.4090303@redhat.com> <54B58AC0.5080805@wiesinger.com> <54B58B18.9060205@redhat.com> <54B595C7.3080101@wiesinger.com> <54B5BF5F.9000805@redhat.com> <54B633CE.3040901@wiesinger.com> <54E05659.9050701@wiesinger.com> <54E1FC2B.3030805@redhat.com> <54E20812.4090006@wiesinger.com> In-Reply-To: <54E20812.4090006@wiesinger.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Fedora FC21 - Bug: 100% CPU and hangs in gettimeofday(&tp, NULL); forever List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gerhard Wiesinger , Laine Stump , qemu-devel@nongnu.org, Cole Robinson , virt@lists.fedoraproject.org On 16/02/2015 16:09, Gerhard Wiesinger wrote: > On 16.02.2015 15:18, Paolo Bonzini wrote: >> >> On 15/02/2015 09:18, Gerhard Wiesinger wrote: >>> >>> Can you grab some random backtraces ("thread apply all bt full") with >>> gdb? > > Very low load on the machine, so I guess most will be sleeping and hard > to catch non sleeping ones. See below This likely means that the 100% threads are not the I/O (event loop) threads, but the VCPU threads. >>> Kernel (host/guest): 3.18.6-200.fc21.x86_64 #1 SMP >>> qemu-kvm-2.2.0-5.fc21.x86_64 >>> >>> Bug 1178975 - endless loop in clock_gettime() on a kvm-based VM >>> https://bugzilla.redhat.com/show_bug.cgi?id=1178975 >>> is fixed (didn't occour with the test program posted at >>> https://bugzilla.redhat.com/show_bug.cgi?id=1178975#c28 in 30min, >>> happened before reproduceable in 2min, still running) >>> >>> So I guess there is another problem in the kernel with volatile and gcc >>> optimizations (or maybe in qemu-KVM) >> No, this doesn't look like volatile. > > But why 100% on 2 cores? Because you have 2 VCPUs, I guess. Paolo