l4-hackers Digest, Vol 105, Issue 5

[Chen Tian]

Hi Adam,

I got another trace:

Chen: caps_alloc for virt addr 0xf081f010 (index 0x1f01), new cap location
0xfec93000, [virt 0xf081f000-> mem 0xfec93000] in space 0xfedd7f08, s = 0x0
 Chen: caps_alloc for virt addr 0xf081f000 (index 0x1f00), new cap location
0xfec92000, [virt 0xf081f000-> mem 0xfec92000] in space 0xfedd7f08, s = 0x0
 thread 0xfed4c000: v_fabricate is false: (Obj_space) from [0xfedd7ef4/12],
s_phys 0x0: 00001f01 size: 00000001 to [0xfedd7e9c/18] recv addr 0x1e8f

KERNEL: Warning: nothing mapped: (Obj_space) from [0xfedd7ef4/12]: 00001f02
size: 00000001 to [0xfedd7e9c/18] recv addr 0x1e90
Chen: v_delete on cap 0xfecf33b4 for virt addr 0x1ef8 (entry addr
0xfec90f80) in space 0xfedd7f08


As you can see,  the status variable "s" is Insert_OK for two invocations
of caps_alloc. That means  mem_space()->v_insert function is not safe
either? Why two insertions are successful at the same time on the same
virtual address?

I have put a lock to protect l4_factory_create_xxx in my application and
that seems to work.

Best,
Chen



On Tue, Jan 17, 2012 at 3:00 AM, <l4-hackers-request at os.inf.tu-dresden.de>wrote:

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>   1. Re: race condition in obj_space-virt.cpp ? (Adam Lackorzynski)
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>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 16 Jan 2012 23:54:07 +0100
> From: Adam Lackorzynski <adam at os.inf.tu-dresden.de>
> To: l4-hackers at os.inf.tu-dresden.de
> Subject: Re: race condition in obj_space-virt.cpp ?
> Message-ID: <20120116225406.GA6550 at os.inf.tu-dresden.de>
> Content-Type: text/plain; charset=iso-8859-1
>
>
> On Fri Jan 13, 2012 at 16:37:06 -0800, Chen Tian wrote:
> > Hello,
> >
> > I observed a race condition in Fiasco.OC. My environment is very
> > complicated, but basically I have multiple threads, and each thread keep
> > creating kernel object via l4_factory_create_xxxx and map the object to a
> > new task.
> >
> > Here is the trace I got:
>
> Thanks, we're looking into this.
>
>
>
> Adam
> --
> Adam                 adam at os.inf.tu-dresden.de
>  Lackorzynski         http://os.inf.tu-dresden.de/~adam/
>
>
>
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> End of l4-hackers Digest, Vol 105, Issue 5
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