From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:48588) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SyOy9-0005eL-Ug for qemu-devel@nongnu.org; Mon, 06 Aug 2012 11:11:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SyOy8-0000ii-LI for qemu-devel@nongnu.org; Mon, 06 Aug 2012 11:11:45 -0400 Received: from mail-lb0-f173.google.com ([209.85.217.173]:56794) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SyOy8-0000iY-DH for qemu-devel@nongnu.org; Mon, 06 Aug 2012 11:11:44 -0400 Received: by lbbgm13 with SMTP id gm13so524511lbb.4 for ; Mon, 06 Aug 2012 08:11:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <4FEC56B2.6050502@dlhnet.de> References: <4FEC56B2.6050502@dlhnet.de> Date: Mon, 6 Aug 2012 16:11:42 +0100 Message-ID: From: Stefan Hajnoczi Content-Type: text/plain; charset=ISO-8859-1 Subject: Re: [Qemu-devel] qemu-kvm-1.0.1 - unable to exit if vcpu is in infinite loop List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Lieven Cc: Jan Kiszka , "qemu-devel@nongnu.org" , "kvm@vger.kernel.org" , Avi Kivity On Thu, Jun 28, 2012 at 2:05 PM, Peter Lieven wrote: > i debugged my initial problem further and found out that the problem happens > to be that > the main thread is stuck in pause_all_vcpus() on reset or quit commands in > the monitor > if one cpu is stuck in the do-while loop kvm_cpu_exec. If I modify the > condition from while (ret == 0) > to while ((ret == 0) && !env->stop); it works, but is this the right fix? > "Quit" command seems to work, but on "Reset" the VM enterns pause state. I think I'm hitting something similar. I installed a F17 amd64 guest (3.5 kernel) but before booting entered the GRUB boot menu edit mode. The guest seemed unresponsive so I switched to the monitor, which also froze shortly afterwards. The VNC screen ended up being all black. qemu-kvm.git/master 3e4305694fd891b69e4450e59ec4c65420907ede Linux 3.2.0-3-amd64 from Debian testing $ qemu-system-x86_64 -enable-kvm -m 1024 -smp 2 -drive if=virtio,cache=none,file=f17.img,aio=native -serial stdio (gdb) thread apply all bt Thread 3 (Thread 0x7f8008e23700 (LWP 367)): #0 0x00007f800f891727 in ioctl () at ../sysdeps/unix/syscall-template.S:82 #1 0x00007f80137b92c9 in kvm_vcpu_ioctl (env=env@entry=0x7f8015b49640, type=type@entry=44672) at /home/stefanha/qemu-kvm/kvm-all.c:1619 #2 0x00007f80137b93fe in kvm_cpu_exec (env=env@entry=0x7f8015b49640) at /home/stefanha/qemu-kvm/kvm-all.c:1506 #3 0x00007f8013766f31 in qemu_kvm_cpu_thread_fn (arg=0x7f8015b49640) at /home/stefanha/qemu-kvm/cpus.c:756 #4 0x00007f800fb4db50 in start_thread (arg=) at pthread_create.c:304 #5 0x00007f800f8986dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112 #6 0x0000000000000000 in ?? () This vcpu is still executing guest code and I've seen it successfully dispatching I/O. The problem is it's missing the exit_request... Thread 2 (Thread 0x7f8008622700 (LWP 368)): #0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162 #1 0x00007f801372b229 in qemu_cond_wait (cond=, mutex=mutex@entry=0x7f80144367c0) at qemu-thread-posix.c:113 #2 0x00007f8013766eff in qemu_kvm_wait_io_event (env=) at /home/stefanha/qemu-kvm/cpus.c:724 #3 qemu_kvm_cpu_thread_fn (arg=0x7f8015b67450) at /home/stefanha/qemu-kvm/cpus.c:761 #4 0x00007f800fb4db50 in start_thread (arg=) at pthread_create.c:304 #5 0x00007f800f8986dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:112 #6 0x0000000000000000 in ?? () No problems here. Thread 1 (Thread 0x7f801347b8c0 (LWP 365)): #0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:162 #1 0x00007f801372b229 in qemu_cond_wait (cond=cond@entry=0x7f801402fd80, mutex=mutex@entry=0x7f80144367c0) at qemu-thread-posix.c:113 #2 0x00007f8013768949 in pause_all_vcpus () at /home/stefanha/qemu-kvm/cpus.c:962 #3 0x00007f80136028c8 in main (argc=, argv=, envp=) at /home/stefanha/qemu-kvm/vl.c:3695 We're deadlocked in pause_all_vcpus(), waiting for vcpu #0 to pause. Unfortunately vcpu #0 has ->exit_request=0 although ->stop=1. Here are the vcpus: (gdb) p first_cpu $6 = (struct CPUX86State *) 0x7f8015b49640 (gdb) p first_cpu->next_cpu $7 = (struct CPUX86State *) 0x7f8015b67450 (gdb) p first_cpu->next_cpu->next_cpu $8 = (struct CPUX86State *) 0x0 (gdb) p first_cpu->stop $9 = 1 (gdb) p first_cpu->stopped $10 = 0 (gdb) p first_cpu->exit_request $11 = 0 :( This isn't easy to reproduce. I tried entering the GRUB boot menu again and there was no deadlock. Stefan