[Qemu-devel] QEMU hangs on sdl/monitor switch

[Luiz Capitulino]

 Hi there,

 I'm getting a strange QEMU hang if a switch fast between the SDL main
screen and the monitor's prompt. This looks like a kernel bug, but I as
can't reproduce with qemu-kvm and as we're in testing phase, I figured I
would report it here first.

 Didn't try on a different machine yet, so could also be some local
issue.

 Here goes the details:

1. Versions

qemu's head: 7dbbbb
qemu-kvm's head: d0be25
kernel: fedora's 2.6.30.9-99.fc11.x86_64

2. How to reproduce

Start qemu with:

$ sudo ./qemu-qmp -hda disks/fedora-11-kratos-i386.img -enable-kvm -m 1G 
-snapshot

Then do the following:

        1. switch to the monitor: ctrl-alt-2
        2. wait one second
        3. switch back to the sdl main screen: ctrl-alt-1
        4. wait one second
        5. repeat

 QEMU will hang before the VM is fully booted.

3. GDB backtrace

I've attached gdb to qemu while it's hung:

#0  0x0000003d524d6827 in ioctl () from /lib64/libc.so.6
#1  0x00000000004295fe in kvm_vcpu_ioctl (env=0x1e409b0, type=44672)
    at /home/lcapitulino/src/qmp-unstable/kvm-all.c:859
#2  0x0000000000428bb7 in kvm_cpu_exec (env=0x1e409b0) at 
/home/lcapitulino/src/qmp-unstable/kvm-all.c:597
#3  0x00000000005177d0 in cpu_x86_exec (env1=0x1e409b0) at 
/home/lcapitulino/src/qmp-unstable/cpu-exec.c:327
#4  0x000000000040c667 in qemu_cpu_exec (env=0x1e409b0) at 
/home/lcapitulino/src/qmp-unstable/vl.c:3948
#5  0x000000000040c75a in tcg_cpu_exec () at 
/home/lcapitulino/src/qmp-unstable/vl.c:3979
#6  0x000000000040ca18 in main_loop () at 
/home/lcapitulino/src/qmp-unstable/vl.c:4094
#7  0x000000000041058a in main (argc=7, argv=0x7fffd5406298, 
envp=0x7fffd54062d8)
    at /home/lcapitulino/src/qmp-unstable/vl.c:5988
The program is running.  Quit anyway (and detach it)? (y or n) Detaching from 
program: /home/lcapitulino/src/qmp-unstable/x86_64-softmmu/qemu-system-x86_64, 
process 3264

4. Additional info

I could reproduce with the old bios but could not reproduce with
qemu-kvm.

Sometimes QEMU will be back running when I quit gdb.

I've attached some sysrq info, for those who want to take a look
at the kernel.

active-cpus.txt
Description: Text document

blocked-tasks.txt
Description: Text document

task-states.txt
Description: Text document