On 2012-08-06 17:11, Stefan Hajnoczi wrote: > On Thu, Jun 28, 2012 at 2:05 PM, Peter Lieven <pl@xxxxxxxxx> 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=<optimized out>) 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=<optimized out>, > mutex=mutex@entry=0x7f80144367c0) at qemu-thread-posix.c:113 > #2 0x00007f8013766eff in qemu_kvm_wait_io_event (env=<optimized out>) > 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=<optimized out>) 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=<optimized out>, argv=<optimized out>, > envp=<optimized out>) 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 CPUState::exit_request is only set on specific synchronous events, see target-i386/kvm.c. More interesting is CPUState::thread_kicked. If it's set, qemu_cpu_kick will skip the kicking via a signal. Maybe there is some race. Let me think about such possibilities again... Jan > > :( > > This isn't easy to reproduce. I tried entering the GRUB boot menu > again and there was no deadlock. > > Stefan > -- Siemens AG, Corporate Technology, CT RTC ITP SDP-DE Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
