Your message dated Thu, 10 Mar 2016 17:34:54 +0000
with message-id <1457631294.3001.54.ca...@decadent.org.uk>
and subject line Re: Bug#817816: System freeze with CPU hotplug
has caused the Debian Bug report #817816,
regarding System freeze with CPU hotplug
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

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-- 
817816: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=817816
Debian Bug Tracking System
Contact ow...@bugs.debian.org with problems
--- Begin Message ---
Package: linux-image-4.4.0-1-amd64
Version: 4.4.4-1
Severity: critical
Justification: renders system unusable


When I run the following commands, the system freezes:

# echo 0 | tee /sys/devices/system/cpu/cpu*/online && echo 1 | sudo tee 
/sys/devices/system/cpu/cpu*/online

The system freezes randomly when the CPUs are being onlined or offlined. The 
system is installed on a VMware virtual machine with 4 processors. Here's a 
stacktrace of the infinite loop:

-----------------------------------------------------------------------------------------------------------------------[regs]
  RAX: 0xFFFFFFFF8160AC40  RBX: 0x0000000000000003  RCX: 0x0000000000000000  
RDX: 0x0000000000000003  o d i t s Z a P c 
  RSI: 0x0000000000000286  RDI: 0xFFFF88004E6B7D98  RBP: 0xFFFF88004E6B7D98  
RSP: 0xFFFF88007CFCFDC0  RIP: 0xFFFFFFFF8110AD52
  R8 : 0xFFFF88007F60F380  R9 : 0x0000000000000000  R10: 0xFFFFFFFF81B004C0  
R11: 0x0000000000000000  R12: 0xFFFF88004E6B7DBC
  R13: 0x0000000000000282  R14: 0xFFFF88007F60F300  R15: 0xFFFFFFFF8110AD10
  CS: 0010  DS: 0000  ES: 0000  FS: 0000  GS: 0000  SS: 0018                    
        
-----------------------------------------------------------------------------------------------------------------------[code]
=> 0xffffffff8110ad52 <multi_cpu_stop+66>:      mov    ebx,DWORD PTR [rbp+0x20]
   0xffffffff8110ad55 <multi_cpu_stop+69>:      cmp    edx,ebx
   0xffffffff8110ad57 <multi_cpu_stop+71>:      je     0xffffffff8110ad74 
<multi_cpu_stop+100>
   0xffffffff8110ad59 <multi_cpu_stop+73>:      cmp    ebx,0x2
   0xffffffff8110ad5c <multi_cpu_stop+76>:      je     0xffffffff8110ad9e 
<multi_cpu_stop+142>
   0xffffffff8110ad5e <multi_cpu_stop+78>:      cmp    ebx,0x3
   0xffffffff8110ad61 <multi_cpu_stop+81>:      jne    0xffffffff8110ad68 
<multi_cpu_stop+88>
   0xffffffff8110ad63 <multi_cpu_stop+83>:      test   r14b,r14b
-----------------------------------------------------------------------------------------------------------------------------
multi_cpu_stop (data=0xffff88004e6b7d98) at 
/build/linux-xT7CCq/linux-4.4.4/kernel/stop_machine.c:197
197     /build/linux-xT7CCq/linux-4.4.4/kernel/stop_machine.c: No such file or 
directory.
gdb$ bt
#0  multi_cpu_stop (data=0xffff88004e6b7d98) at 
/build/linux-xT7CCq/linux-4.4.4/kernel/stop_machine.c:197
#1  0xffffffff8110afed in cpu_stopper_thread (cpu=<optimized out>) at 
/build/linux-xT7CCq/linux-4.4.4/kernel/stop_machine.c:456
#2  0xffffffff81097d49 in smpboot_thread_fn (data=0xffff88004e6b7d98) at 
/build/linux-xT7CCq/linux-4.4.4/kernel/smpboot.c:163
#3  0xffffffff81094dfd in kthread (_create=0xffff88007ce82100) at 
/build/linux-xT7CCq/linux-4.4.4/kernel/kthread.c:209
#4  0xffffffff8158ed8f in ret_from_fork () at 
/build/linux-xT7CCq/linux-4.4.4/arch/x86/entry/entry_64.S:486
#5  0x0000000000000000 in ?? ()
gdb$ x/x $rbp+0x20
0xffff88004e6b7db8:     0x00000003

In the function multi_cpu_stop(), curstate equals MULTI_STOP_RUN and seems to 
never become equal to MULTI_STOP_EXIT. Let me know if you require additional 
informations.
Thanks                                    

--- End Message ---
--- Begin Message ---
On Thu, 2016-03-10 at 17:32 +0100, Harry Junior wrote:
> Package: linux-image-4.4.0-1-amd64
> Version: 4.4.4-1
> Severity: critical
> Justification: renders system unusable
> 
> 
> When I run the following commands, the system freezes:
> 
> # echo 0 | tee /sys/devices/system/cpu/cpu*/online && echo 1 | sudo
> tee /sys/devices/system/cpu/cpu*/online
> 
> The system freezes randomly when the CPUs are being onlined or
> offlined. The system is installed on a VMware virtual machine with 4
> processors. Here's a stacktrace of the infinite loop:
[...]

You just asked to offline all CPUs, making the system unusable.  I
don't see any bug here.

Ben.

-- 
Ben Hutchings
To err is human; to really foul things up requires a computer.

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