[Qemu-devel] [Bug 1490853] Re: qemu windows guest hangs on 100% cpu usage
[Expired for QEMU because there has been no activity for 60 days.] ** Changed in: qemu Status: Incomplete => Expired -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1490853 Title: qemu windows guest hangs on 100% cpu usage Status in QEMU: Expired Bug description: hi: I have two VM , one is winXP Prefessional SP3 32bit, another one is WindowsServer2008 Enterprise SP2 64bit. When I hot reboot winXP in guest OS, it'll hangs on progress bar, and all the vcpu thread in qemu is 100% usage. There are no message in kernel log when it happened, I try to rebuild kvm and add some debug info , I found the cpu exit reason is EXIT_REASON_PAUSE_INSTRUCTION. It seems like all the vcpu always in spinlock waiting. I'm not sure whether it's qemu's bug or kvm's. Any help would be appreciated. How reproducible: WinXP: seems always. WinServer2008: rare. Steps to Reproduce: winXP: hot reboot the xp guest os, hot reboot is necessary. WinServer2008: not sure, I didn't do anything, it just happened. The different between WinXP and WInServer2008: 1. When WinXP hangs, the boot progress bar is rolling, I think that vnc is work fine. 2. When WinServer2008 hangs, the vnc show the last screen and the screen won't change anything include system time. 3. When the VM hangs , if I execute "virsh suspend vm-name" and "virsh resume vm-name", the WinServer2008 will change to normal , and work fine not hangs anymore. But WinXP not change anything, still hangs. qemu version: QEMU emulator version 1.5.0, Copyright (c) 2003-2008 Fabrice Bellard host info: Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz Ubuntu 12.04 LTS \n \l Linux cvknode2026 3.13.6 #1 SMP Fri Dec 12 09:17:35 CST 2014 x86_64 x86_64 x86_64 GNU/Linux qemu command line (guest OS XP): root 7124 1178 7.6 7750360 3761644 ? Sl 14:02 435:23 /usr/bin/kvm -name x -S -machine pc-i440fx-1.5,accel=kvm,usb=off,system=windows -cpu qemu64,hv_relaxed,hv_spinlocks=0x2000 -m 6144 -smp 12,maxcpus=72,sockets=12,cores=6,threads=1 -uuid d3832129-f77d-4b21-bbf7-fd337f53e572 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/x.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime,clock=vm,driftfix=slew -no-hpet -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device usb-ehci,id=ehci,bus=pci.0,addr=0x4 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive file=/vms/images/sn1-of-ff.qcow2,if=none,id=drive-ide0-0-0,format=qcow2,cache=directsync -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive if=none,id=drive-ide0-1-1,readonly=on,format=raw -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1,bootindex=2 -netdev tap,fd=24,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=0c:da:41:1d:f8:40,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/x.agent,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -device usb-tablet,id=input0,bus=usb.0 -vnc 0.0.0.0:0 -device VGA,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 all qemu thread (guest OS XP): root@cvknode2026:/proc/7124/task# top -d 1 -H -p 7124 top - 14:37:05 up 7 days, 4:07, 1 user, load average: 10.71, 10.90, 10.19 Tasks: 14 total, 12 running, 2 sleeping, 0 stopped, 0 zombie Cpu(s): 38.8%us, 11.2%sy, 0.0%ni, 50.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 49159888k total, 35665128k used, 13494760k free, 436312k buffers Swap: 8803324k total,0k used, 8803324k free, 28595100k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ P SWAP WCHAN COMMAND 7130 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.48 3 3.8g - kvm 7132 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.13 1 3.8g - kvm 7133 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.70 6 3.8g - kvm 7135 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.33 11 3.8g - kvm 7137 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.59 17 3.8g - kvm 7126 root 20 0 7568m 3.6g 6628 R 100 7.7 34:06.76 4 3.8g - kvm 7127 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.14 8 3.8g - kvm 7128 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 13 3.8g - kvm 7129 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 7 3.8g - kvm 7131 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.24 10 3.8g - kvm 7134 root 20 0 7568m 3.6g 6628 R 100 7.7 33:42.47 12 3.8g - kvm 7136 root 20 0 7568m 3.6g 6628 R 100
[Qemu-devel] [Bug 1490853] Re: qemu windows guest hangs on 100% cpu usage
Triaging old bug tickets... can you still reproduce this issue with the latest version of QEMU? Or could we close this ticket nowadays? ** Changed in: qemu Status: New => Incomplete -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1490853 Title: qemu windows guest hangs on 100% cpu usage Status in QEMU: Incomplete Bug description: hi: I have two VM , one is winXP Prefessional SP3 32bit, another one is WindowsServer2008 Enterprise SP2 64bit. When I hot reboot winXP in guest OS, it'll hangs on progress bar, and all the vcpu thread in qemu is 100% usage. There are no message in kernel log when it happened, I try to rebuild kvm and add some debug info , I found the cpu exit reason is EXIT_REASON_PAUSE_INSTRUCTION. It seems like all the vcpu always in spinlock waiting. I'm not sure whether it's qemu's bug or kvm's. Any help would be appreciated. How reproducible: WinXP: seems always. WinServer2008: rare. Steps to Reproduce: winXP: hot reboot the xp guest os, hot reboot is necessary. WinServer2008: not sure, I didn't do anything, it just happened. The different between WinXP and WInServer2008: 1. When WinXP hangs, the boot progress bar is rolling, I think that vnc is work fine. 2. When WinServer2008 hangs, the vnc show the last screen and the screen won't change anything include system time. 3. When the VM hangs , if I execute "virsh suspend vm-name" and "virsh resume vm-name", the WinServer2008 will change to normal , and work fine not hangs anymore. But WinXP not change anything, still hangs. qemu version: QEMU emulator version 1.5.0, Copyright (c) 2003-2008 Fabrice Bellard host info: Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz Ubuntu 12.04 LTS \n \l Linux cvknode2026 3.13.6 #1 SMP Fri Dec 12 09:17:35 CST 2014 x86_64 x86_64 x86_64 GNU/Linux qemu command line (guest OS XP): root 7124 1178 7.6 7750360 3761644 ? Sl 14:02 435:23 /usr/bin/kvm -name x -S -machine pc-i440fx-1.5,accel=kvm,usb=off,system=windows -cpu qemu64,hv_relaxed,hv_spinlocks=0x2000 -m 6144 -smp 12,maxcpus=72,sockets=12,cores=6,threads=1 -uuid d3832129-f77d-4b21-bbf7-fd337f53e572 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/x.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime,clock=vm,driftfix=slew -no-hpet -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device usb-ehci,id=ehci,bus=pci.0,addr=0x4 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive file=/vms/images/sn1-of-ff.qcow2,if=none,id=drive-ide0-0-0,format=qcow2,cache=directsync -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive if=none,id=drive-ide0-1-1,readonly=on,format=raw -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1,bootindex=2 -netdev tap,fd=24,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=0c:da:41:1d:f8:40,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/x.agent,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -device usb-tablet,id=input0,bus=usb.0 -vnc 0.0.0.0:0 -device VGA,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 all qemu thread (guest OS XP): root@cvknode2026:/proc/7124/task# top -d 1 -H -p 7124 top - 14:37:05 up 7 days, 4:07, 1 user, load average: 10.71, 10.90, 10.19 Tasks: 14 total, 12 running, 2 sleeping, 0 stopped, 0 zombie Cpu(s): 38.8%us, 11.2%sy, 0.0%ni, 50.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 49159888k total, 35665128k used, 13494760k free, 436312k buffers Swap: 8803324k total,0k used, 8803324k free, 28595100k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ P SWAP WCHAN COMMAND 7130 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.48 3 3.8g - kvm 7132 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.13 1 3.8g - kvm 7133 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.70 6 3.8g - kvm 7135 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.33 11 3.8g - kvm 7137 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.59 17 3.8g - kvm 7126 root 20 0 7568m 3.6g 6628 R 100 7.7 34:06.76 4 3.8g - kvm 7127 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.14 8 3.8g - kvm 7128 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 13 3.8g - kvm 7129 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 7 3.8g - kvm 7131 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.24 10 3.8g - kvm 7134 root 20 0 7568m 3.6g 6628 R 100 7.7 33:42.47 12
[Qemu-devel] [Bug 1490853] Re: qemu windows guest hangs on 100% cpu usage
** Description changed: hi: I have two VM , one is winXP Prefessional SP3 32bit, another one is WindowsServer2008 Enterprise SP2 64bit. When I hot reboot winXP in guest OS, it'll hangs on progress bar, and all the vcpu thread in qemu is 100% usage. - I try to rebuild kvm and add some debug info , I found the cpu exit reason is EXIT_REASON_PAUSE_INSTRUCTION. + There are no message in kernel log when it happened, I try to rebuild kvm and add some debug info , I found the cpu exit reason is EXIT_REASON_PAUSE_INSTRUCTION. It seems like all the vcpu always in spinlock waiting. I'm not sure whether it's qemu's bug or kvm's. Any help would be appreciated. How reproducible: WinXP: seems always. WinServer2008: rare. Steps to Reproduce: winXP: hot reboot the xp guest os, hot reboot is necessary. WinServer2008: not sure, I didn't do anything, it just happened. The different between WinXP and WInServer2008: 1. When WinXP hangs, the boot progress bar is rolling, I think that vnc is work fine. 2. When WinServer2008 hangs, the vnc show the last screen and the screen won't change anything include system time. 3. When the VM hangs , if I execute "virsh suspend vm-name" and "virsh resume vm-name", the WinServer2008 will change to normal , and work fine not hangs anymore. But WinXP not change anything, still hangs. qemu version: QEMU emulator version 1.5.0, Copyright (c) 2003-2008 Fabrice Bellard host info: Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz Ubuntu 12.04 LTS \n \l Linux cvknode2026 3.13.6 #1 SMP Fri Dec 12 09:17:35 CST 2014 x86_64 x86_64 x86_64 GNU/Linux qemu command line (guest OS XP): root 7124 1178 7.6 7750360 3761644 ? Sl 14:02 435:23 /usr/bin/kvm -name x -S -machine pc-i440fx-1.5,accel=kvm,usb=off,system=windows -cpu qemu64,hv_relaxed,hv_spinlocks=0x2000 -m 6144 -smp 12,maxcpus=72,sockets=12,cores=6,threads=1 -uuid d3832129-f77d-4b21-bbf7-fd337f53e572 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/x.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime,clock=vm,driftfix=slew -no-hpet -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device usb-ehci,id=ehci,bus=pci.0,addr=0x4 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive file=/vms/images/sn1-of-ff.qcow2,if=none,id=drive-ide0-0-0,format=qcow2,cache=directsync -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive if=none,id=drive-ide0-1-1,readonly=on,format=raw -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1,bootindex=2 -netdev tap,fd=24,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=0c:da:41:1d:f8:40,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/x.agent,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -device usb-tablet,id=input0,bus=usb.0 -vnc 0.0.0.0:0 -device VGA,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 all qemu thread (guest OS XP): root@cvknode2026:/proc/7124/task# top -d 1 -H -p 7124 top - 14:37:05 up 7 days, 4:07, 1 user, load average: 10.71, 10.90, 10.19 Tasks: 14 total, 12 running, 2 sleeping, 0 stopped, 0 zombie Cpu(s): 38.8%us, 11.2%sy, 0.0%ni, 50.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 49159888k total, 35665128k used, 13494760k free, 436312k buffers Swap: 8803324k total,0k used, 8803324k free, 28595100k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ P SWAP WCHAN COMMAND 7130 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.48 3 3.8g - kvm 7132 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.13 1 3.8g - kvm 7133 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.70 6 3.8g - kvm 7135 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.33 11 3.8g - kvm 7137 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.59 17 3.8g - kvm 7126 root 20 0 7568m 3.6g 6628 R 100 7.7 34:06.76 4 3.8g - kvm 7127 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.14 8 3.8g - kvm 7128 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 13 3.8g - kvm 7129 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 7 3.8g - kvm 7131 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.24 10 3.8g - kvm 7134 root 20 0 7568m 3.6g 6628 R 100 7.7 33:42.47 12 3.8g - kvm 7136 root 20 0 7568m 3.6g 6628 R 100 7.7 33:42.16 2 3.8g - kvm 7124 root 20 0 7568m 3.6g 6628 S1 7.7 0:30.65 14 3.8g poll_sche kvm 7139 root 20 0 7568m 3.6g 6628 S0 7.7 0:01.71 14 3.8g futex_wai kvm all
[Qemu-devel] [Bug 1490853] Re: qemu windows guest hangs on 100% cpu usage
** Description changed: hi: I have two VM , one is winXP Prefessional SP3 32bit, another one is WindowsServer2008 Enterprise SP2 64bit. When I hot reboot winXP in guest OS, it'll hangs on progress bar, and all the vcpu thread in qemu is 100% usage. I try to rebuild kvm and add some debug info , I found the cpu exit reason is EXIT_REASON_PAUSE_INSTRUCTION. It seems like all the vcpu always in spinlock waiting. I'm not sure whether it's qemu's bug or kvm's. Any help would be appreciated. How reproducible: WinXP: seems always. WinServer2008: rare. Steps to Reproduce: - winXP: 1. hot reboot the xp guest os, hot reboot is necessary. + winXP: hot reboot the xp guest os, hot reboot is necessary. WinServer2008: not sure, I didn't do anything, it just happened. The different between WinXP and WInServer2008: 1. When WinXP hangs, the boot progress bar is rolling, I think that vnc is work fine. 2. When WinServer2008 hangs, the vnc show the last screen and the screen won't change anything include system time. 3. When the VM hangs , if I execute "virsh suspend vm-name" and "virsh resume vm-name", the WinServer2008 will change to normal , and work fine not hangs anymore. But WinXP not change anything, still hangs. qemu version: QEMU emulator version 1.5.0, Copyright (c) 2003-2008 Fabrice Bellard + host info: + Intel(R) Xeon(R) CPU E5-2620 0 @ 2.00GHz Ubuntu 12.04 LTS \n \l Linux cvknode2026 3.13.6 #1 SMP Fri Dec 12 09:17:35 CST 2014 x86_64 x86_64 x86_64 GNU/Linux qemu command line (guest OS XP): root 7124 1178 7.6 7750360 3761644 ? Sl 14:02 435:23 /usr/bin/kvm -name x -S -machine pc-i440fx-1.5,accel=kvm,usb=off,system=windows -cpu qemu64,hv_relaxed,hv_spinlocks=0x2000 -m 6144 -smp 12,maxcpus=72,sockets=12,cores=6,threads=1 -uuid d3832129-f77d-4b21-bbf7-fd337f53e572 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/x.monitor,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime,clock=vm,driftfix=slew -no-hpet -no-shutdown -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device usb-ehci,id=ehci,bus=pci.0,addr=0x4 -device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 -drive file=/vms/images/sn1-of-ff.qcow2,if=none,id=drive-ide0-0-0,format=qcow2,cache=directsync -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 -drive if=none,id=drive-ide0-1-1,readonly=on,format=raw -device ide-cd,bus=ide.1,unit=1,drive=drive-ide0-1-1,id=ide0-1-1,bootindex=2 -netdev tap,fd=24,id=hostnet0 -device rtl8139,netdev=hostnet0,id=net0,mac=0c:da:41:1d:f8:40,bus=pci.0,addr=0x3 -chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/x.agent,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 -device usb-tablet,id=input0,bus=usb.0 -vnc 0.0.0.0:0 -device VGA,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 all qemu thread (guest OS XP): root@cvknode2026:/proc/7124/task# top -d 1 -H -p 7124 top - 14:37:05 up 7 days, 4:07, 1 user, load average: 10.71, 10.90, 10.19 Tasks: 14 total, 12 running, 2 sleeping, 0 stopped, 0 zombie Cpu(s): 38.8%us, 11.2%sy, 0.0%ni, 50.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 49159888k total, 35665128k used, 13494760k free, 436312k buffers Swap: 8803324k total,0k used, 8803324k free, 28595100k cached PID USER PR NI VIRT RES SHR S %CPU %MEMTIME+ P SWAP WCHAN COMMAND 7130 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.48 3 3.8g - kvm 7132 root 20 0 7568m 3.6g 6628 R 101 7.7 33:43.13 1 3.8g - kvm 7133 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.70 6 3.8g - kvm 7135 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.33 11 3.8g - kvm 7137 root 20 0 7568m 3.6g 6628 R 101 7.7 33:42.59 17 3.8g - kvm 7126 root 20 0 7568m 3.6g 6628 R 100 7.7 34:06.76 4 3.8g - kvm 7127 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.14 8 3.8g - kvm 7128 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 13 3.8g - kvm 7129 root 20 0 7568m 3.6g 6628 R 100 7.7 33:43.64 7 3.8g - kvm 7131 root 20 0 7568m 3.6g 6628 R 100 7.7 33:44.24 10 3.8g - kvm 7134 root 20 0 7568m 3.6g 6628 R 100 7.7 33:42.47 12 3.8g - kvm 7136 root 20 0 7568m 3.6g 6628 R 100 7.7 33:42.16 2 3.8g - kvm 7124 root 20 0 7568m 3.6g 6628 S1 7.7 0:30.65 14 3.8g poll_sche kvm 7139 root 20 0 7568m 3.6g 6628 S0 7.7 0:01.71 14 3.8g futex_wai kvm all thread's kernel stack (guest OS XP): root@cvknode2026:/proc/7124/task# cat 7130/stack []
