[Qemu-devel] QEMU temporarily hangs

[Qemu-devel] QEMU temporarily hangs

[Uri Lublin]

Hello,

Second attempt (with minor modifications), as the
first one did not arrive.

I would like to share with you a QEMU problem I've
encountered,
    and hope to get pointers where to look for it.
I am running CVS QEMU, x86_64-softmmu, with vmdk image
and redirected monitor
    (unix socket).

If the guest is busy and I rapidly send a LOT of
commands to QEMU monitor,
    then eventually QEMU temporarily hangs (vnc and
monitor are not responsive)
At that state:
 - QEMU process's cpu usage is around 100%
 - strace shows ONLY clock_gettime(CLOCK_MONOTONIC,
{time changing}) = 0
 - pstack shows:
      #0  0x0000003603e0459b in clock_gettime () from
/lib64/librt.so.1
      #1  0x0000000000405c9d in get_clock ()
      #2  0x0000000000405d65 in cpu_get_clock ()
      #3  0x000000000044f660 in pit_get_count ()
      #4  0x000000000044f805 in pit_latch_count ()
      #5  0x0000000002450ec8 in code_gen_buffer ()
      #6  0xbe26f6118053c79f in ?? ()
      #7  0x000000000047df6e in cpu_x86_exec ()
      #8  0x000000000040c11a in main_loop ()
      #9  0x000000000040da69 in main ()


After a while (few or more minutes), it comes back to
life.
I can shorten my waiting time by sending a SIGUSR2
signal to QEMU (SIGIO and SIGALRM work too).
Why doesn't host_alarm_handler() get called/bring QEMU
back to life ?

Any comment would be appreciated,
Thanks,
    Uri.


 
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