Re: [Qemu-devel] Qemu savevm and CPU soft lockup

[Benjamin Cleyet-Marrel <bcm@accelance.fr>]

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Hi, 

After further investigation, I figured out that when issuing a savevm
command
the entire qemu process gets stuck on IO wait.
I can't issue any other commands on the monitor the process is shown as
D and the guest is in softlockup state.

Looking at the way migrate (and the -d for detach I presume) is working
I suppose the same behaviour would be expected from the savevm function.

A savevm -d so that the qemu process would not be freezed while saving
the data.

Sorry if I am just talking non sense but my snapshot on iscsi storage
takes about 1 minutes. 
which means that my guest are down for a minute or so which is not
ideal.

Thanks for your time
Cheers
Ben


-------- Message initial --------
De: Benjamin Cleyet-Marrel <bcm@accelance.fr>
À: qemu-devel@nongnu.org
Sujet: [Qemu-devel] Qemu savevm and CPU soft lockup
Date: Fri, 18 Sep 2009 11:56:41 +0200

Hi, 

First post to this list so sorry if I am mistaken.
I am using qemu-kvm-0.11.0-rc2 I've googled quite a lot and could not
find anyone having or reporting the same problem.
The guest is a Centos5.3

The savevm/loadvm seems to be broken:

When issuing a savevm in the monitor, 
Guest get stuck for a few seconds and I get the infamous soft lockup a
couple of time. (see bellow)

In the end, the snapshot is working.

When doing a loadvm I often get weird behaviour on the console.
this can be completly removed if I issue a stop and cont before and
after the loadvm.

Question is:
Am I doing something wrong or is this a bug ?

Thanks
Cheers
Ben



Sep 18 10:58:48 dhcp155 kernel: BUG: soft lockup - CPU#0 stuck for 10s!
[swapper:0]
Sep 18 10:58:48 dhcp155 kernel: 
Sep 18 10:58:48 dhcp155 kernel: Pid: 0, comm:              swapper
Sep 18 10:58:48 dhcp155 kernel: EIP: 0060:[<c044d219>] CPU: 0
Sep 18 10:58:48 dhcp155 kernel: EIP is at handle_IRQ_event+0x39/0x8c
Sep 18 10:58:48 dhcp155 kernel:  EFLAGS: 00000246    Not tainted
(2.6.18-128.el5 #1)
Sep 18 10:58:48 dhcp155 kernel: EAX: 00000001 EBX: c06e6f00 ECX:
f7c9bf80 EDX: c0754f9c
Sep 18 10:58:48 dhcp155 kernel: ESI: f7c9bf80 EDI: 00000001 EBP:
00000000 DS: 007b ES: 007b
Sep 18 10:58:48 dhcp155 kernel: CR0: 8005003b CR2: 080c3e80 CR3:
376ad000 CR4: 00000690
Sep 18 10:58:48 dhcp155 kernel:  [<c044d2f0>] __do_IRQ+0x84/0xd6
Sep 18 10:58:48 dhcp155 kernel:  [<c04074e5>] do_IRQ+0xb0/0xc3
Sep 18 10:58:48 dhcp155 kernel:  [<c0405946>] common_interrupt+0x1a/0x20
Sep 18 10:58:48 dhcp155 kernel:  [<c044d219>] handle_IRQ_event+0x39/0x8c
Sep 18 10:58:48 dhcp155 kernel:  [<c044d2f0>] __do_IRQ+0x84/0xd6
Sep 18 10:58:48 dhcp155 kernel:  [<c044d26c>] __do_IRQ+0x0/0xd6
Sep 18 10:58:48 dhcp155 kernel:  [<c04074ce>] do_IRQ+0x99/0xc3
Sep 18 10:58:48 dhcp155 kernel:  [<c0405946>] common_interrupt+0x1a/0x20
Sep 18 10:58:48 dhcp155 kernel:  [<c0428ba7>] __do_softirq+0x57/0x114
Sep 18 10:58:48 dhcp155 kernel:  [<c04073eb>] do_softirq+0x52/0x9c
Sep 18 10:58:48 dhcp155 kernel:  [<c04059d7>] apic_timer_interrupt
+0x1f/0x24
Sep 18 10:58:48 dhcp155 kernel:  [<c0403bb0>] default_idle+0x0/0x59
Sep 18 10:58:48 dhcp155 kernel:  [<c0403be1>] default_idle+0x31/0x59
Sep 18 10:58:48 dhcp155 kernel:  [<c0403ca8>] cpu_idle+0x9f/0xb9
Sep 18 10:58:48 dhcp155 kernel:  [<c06f59ee>] start_kernel+0x379/0x380
Sep 18 10:58:48 dhcp155 kernel:  =======================


in dmesg




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