Re: panic with overcommit and RACCT

On 5/15/12 1:23 AM, Andrey Zonov wrote:
> On 5/14/12 12:29 AM, Mateusz Guzik wrote:
>> On Sun, May 13, 2012 at 09:27:11PM +0400, Andrey Zonov wrote:
>>> Hi,
>>>
>>> I've got a repeatable panic on latest 9.0-STABLE and HEAD with
>>> turned on overcommit (vm.overcommit=1) and RACCT.
>>>
>>> kgdb trace on today's HEAD:
>>>
>>> #10 0xffffffff80bc3513 in calltrap ()
>>> at /usr/src/sys/amd64/amd64/exception.S:228
>>> #11 0xffffffff808aab71 in racct_set_locked (p=0xfffffe0005d684a0,
>>> resource=0,
>>> amount=2680) at /usr/src/sys/kern/kern_racct.c:372
>>> #12 0xffffffff808ab645 in racct_proc_exit (p=0xfffffe0005d684a0)
>>> at /usr/src/sys/kern/kern_racct.c:615
>>> #13 0xffffffff80880d69 in fork1 (td=0xfffffe0005b2c460, flags=20,
>>> pages=4,
>>> procp=0xffffff811a36bb00, procdescp=Variable "procdescp" is not
>>> available.
>>> ) at /usr/src/sys/kern/kern_fork.c:943
>>> #14 0xffffffff80882362 in sys_fork (td=0xfffffe0005b2c460,
>>> uap=Variable "uap" is not available.
>>> )
>>> at /usr/src/sys/kern/kern_fork.c:110
>>> #15 0xffffffff80bd7a89 in amd64_syscall (td=0xfffffe0005b2c460,
>>> traced=0)
>>> at subr_syscall.c:135
>>> #16 0xffffffff80bc37f7 in Xfast_syscall ()
>>> at /usr/src/sys/amd64/amd64/exception.S:387
>>> #17 0x00000008024729fc in ?? ()
>>> Previous frame inner to this frame (corrupt stack?)
>>> (kgdb)
>>>
>>> Unread portion of the kernel message buffer:
>>> Kernel page fault with the following non-sleepable locks held:
>>> exclusive sleep mutex racct lock (racct lock) r = 0
>>> (0xffffffff8128a7c0) locked @ /usr/src/sys/kern/kern_racct.c:614
>>> exclusive sleep mutex process lock (process lock) r = 0
>>> (0xfffffe0005d68598) locked @ /usr/src/sys/kern/kern_racct.c:603
>>>
>>
>> It looks like racct_proc_exit can be called for processes without
>> properly initialized racct structure, which in turn results in this
>> panic.
>>
>> Can you please test this patch:
>> http://student.agh.edu.pl/~mjguzik/patches/racct-fork.patch
>>
>> ?
>>
>> I was unable to reproduce panic you describe, so it was tested only by
>> manually injecting error. Nevertheless I think you should try it. :)
>>
>
> Thanks, your patch fixes the panic.

Can anyone commit this fix?

>
> How to repeat:
> 1. add options RACCT and options RCTL to kernel config, rebuild and
> install kernel, reboot
> 2. set sysctl vm.overcommit=1
> 3. run as none root something that eats memory (I just run malloc()
> until it returns NULL)
> 4. swapoff -a
> 5. panic after sometime
>
> With patch applied instead of panic I got: "fork: Cannot allocate
> memory". Looks like a bug in overcommit code.
>

-- 
Andrey Zonov
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