Re: [Qemu-devel] [PATCH 0/3] another round of qemu-char fixes

[Gerd Hoffmann <kraxel@redhat.com>]

On 04/17/13 12:17, Paolo Bonzini wrote:
> Il 17/04/2013 09:06, Gerd Hoffmann ha scritto:
>>>> cheers,
>>>>   Gerd
>> Trapped into the next issue.  Added qmp monitor to the virtual machine,
>> linked to unix socket.  Start playing with the qom-* scrips in QMP.
>> qemu hangs after the first qmp-list command (triggered by socket
>> disconnect?).
> 
> Hmm, I cannot reproduce this. 
> 
> x86_64-softmmu/qemu-system-x86_64 -qmp unix:/home/pbonzini/qmp.sock,nowait,server -vnc :1
> 
> (Tried also without nowait, with SDL or -nographic, with KVM, with an additional
> "-serial mon:stdio").
> 
> Multiple executions of "./qom-list -s /home/pbonzini/qmp.sock /machine" work,
> both with and without these three patches.

Hmm.  I'm running with a bunch of monitors actually, maybe that makes
the difference.  qemu is started via libvirt:

rincewind root ~# virsh dumpxml fedora-org-virtio
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'>
  <name>fedora-org-virtio</name>
[ ... ]
  <qemu:commandline>
    <qemu:arg value='-readconfig'/>
    <qemu:arg value='/root/libvirt/fedora-mon.cfg'/>
[ ... ]
rincewind root ~# cat /root/libvirt/fedora-mon.cfg
[chardev "hmp"]
  backend = "socket"
  path = "/root/mon/fedora"
  server = "on"
  wait = "off"

[chardev "qmp"]
  backend = "socket"
  path = "/root/mon/fedora.qmp"
  server = "on"
  wait = "off"

[mon]
  chardev = "hmp"

[mon]
  chardev = "qmp"
  mode = "control"


Hangs here:

(gdb) thread apply all bt

Thread 6 (Thread 0x7f902919b700 (LWP 27869)):
#0  sem_timedwait () at
../nptl/sysdeps/unix/sysv/linux/x86_64/sem_timedwait.S:106
#1  0x00007f90385307f3 in qemu_sem_timedwait (sem=0x7f903abe0978,
ms=<value optimized out>)
    at /home/kraxel/projects/qemu/util/qemu-thread-posix.c:237
#2  0x00007f90383e835e in worker_thread (opaque=0x7f903abe08e0)
    at /home/kraxel/projects/qemu/thread-pool.c:96
#3  0x00007f90366a7851 in start_thread (arg=0x7f902919b700) at
pthread_create.c:301
#4  0x00007f9030bf890d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Thread 5 (Thread 0x7f901cfc7700 (LWP 27870)):
#0  __lll_lock_wait () at
../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136
#1  0x00007f90366a9388 in _L_lock_854 () from /lib64/libpthread.so.0
#2  0x00007f90366a9257 in __pthread_mutex_lock (mutex=0x7f9038d5af20) at
pthread_mutex_lock.c:61
#3  0x00007f9038530c99 in qemu_mutex_lock (mutex=<value optimized out>)
    at /home/kraxel/projects/qemu/util/qemu-thread-posix.c:57
#4  0x00007f9038476f95 in kvm_cpu_exec (env=0x7f903fe6f680)
    at /home/kraxel/projects/qemu/kvm-all.c:1558
#5  0x00007f9038420b41 in qemu_kvm_cpu_thread_fn (arg=0x7f903fe6f680)
    at /home/kraxel/projects/qemu/cpus.c:759
#6  0x00007f90366a7851 in start_thread (arg=0x7f901cfc7700) at
pthread_create.c:301
#7  0x00007f9030bf890d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Thread 4 (Thread 0x7f9017fff700 (LWP 27871)):
#0  0x00007f9030bf0a47 in ioctl () at ../sysdeps/unix/syscall-template.S:82
#1  0x00007f9038474969 in kvm_vcpu_ioctl (cpu=<value optimized out>,
type=<value optimized out>)
    at /home/kraxel/projects/qemu/kvm-all.c:1667
#2  0x00007f9038476f8d in kvm_cpu_exec (env=0x7f903fea1090)
    at /home/kraxel/projects/qemu/kvm-all.c:1556
#3  0x00007f9038420b41 in qemu_kvm_cpu_thread_fn (arg=0x7f903fea1090)
    at /home/kraxel/projects/qemu/cpus.c:759
#4  0x00007f90366a7851 in start_thread (arg=0x7f9017fff700) at
pthread_create.c:301
#5  0x00007f9030bf890d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Thread 3 (Thread 0x7f90161ff700 (LWP 27881)):
#0  0x00007f9030bef253 in __poll (fds=<value optimized out>, nfds=<value
optimized out>,
    timeout=<value optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:87
#1  0x00007f9031815eac in red_worker_main (arg=<value optimized out>) at
red_worker.c:11871
#2  0x00007f90366a7851 in start_thread (arg=0x7f90161ff700) at
pthread_create.c:301
#3  0x00007f9030bf890d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Thread 2 (Thread 0x7f8f4bfff700 (LWP 27882)):
#0  0x00007f9030bef253 in __poll (fds=<value optimized out>, nfds=<value
optimized out>,
    timeout=<value optimized out>) at ../sysdeps/unix/sysv/linux/poll.c:87
#1  0x00007f9031815eac in red_worker_main (arg=<value optimized out>) at
red_worker.c:11871
#2  0x00007f90366a7851 in start_thread (arg=0x7f8f4bfff700) at
pthread_create.c:301
#3  0x00007f9030bf890d in clone () at
../sysdeps/unix/sysv/linux/x86_64/clone.S:115

Thread 1 (Thread 0x7f9038188980 (LWP 27849)):
---Type <return> to continue, or q <return> to quit---
#0  __lll_lock_wait () at
../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:136
#1  0x00007f90366a9388 in _L_lock_854 () from /lib64/libpthread.so.0
#2  0x00007f90366a9257 in __pthread_mutex_lock (mutex=0x7f903abb1538) at
pthread_mutex_lock.c:61
#3  0x00007f9037903c37 in ?? () from /lib64/libglib-2.0.so.0
#4  0x00007f90383c5d96 in io_watch_poll_finalize (source=<value
optimized out>)
    at /home/kraxel/projects/qemu/qemu-char.c:648
#5  0x00007f903790382a in ?? () from /lib64/libglib-2.0.so.0
#6  0x00007f9037903b85 in ?? () from /lib64/libglib-2.0.so.0
#7  0x00007f903790616e in g_source_remove () from /lib64/libglib-2.0.so.0
#8  0x00007f90383c6645 in tcp_chr_read (chan=<value optimized out>,
cond=<value optimized out>,
    opaque=0x7f903abb2fd0) at /home/kraxel/projects/qemu/qemu-char.c:2523
#9  0x00007f9037903f0e in g_main_context_dispatch () from
/lib64/libglib-2.0.so.0
#10 0x00007f903839ee09 in glib_pollfds_poll (nonblocking=<value
optimized out>)
    at /home/kraxel/projects/qemu/main-loop.c:187
#11 os_host_main_loop_wait (nonblocking=<value optimized out>)
    at /home/kraxel/projects/qemu/main-loop.c:232
#12 main_loop_wait (nonblocking=<value optimized out>)
    at /home/kraxel/projects/qemu/main-loop.c:468
#13 0x00007f90384168e5 in main_loop (argc=<value optimized out>,
argv=<value optimized out>,
    envp=<value optimized out>) at /home/kraxel/projects/qemu/vl.c:1990
#14 main (argc=<value optimized out>, argv=<value optimized out>,
envp=<value optimized out>)
    at /home/kraxel/projects/qemu/vl.c:4379