IPC between Tasks

Tobias Fink tobias.fink at stud.h-da.de
Wed Jun 13 16:13:12 CEST 2012

Right now I'm examining the example included in L4Re:
This exists at this point:

if (l4shmc_create("testshm", 8192))
    return 1;

I'm testing on an IGEPv2 Board with a DM3730 ARM Cortex-A8 processor.
What am I missing?

Here is the output from the Boot process:

SIGMA0: Hello!
  KIP @ 80002000
  allocated 4KB for maintenance structures
SIGMA0: Dump of all resource maps
MOE: Hello world
MOE: found 112192 KByte free memory
MOE: found RAM from 80000000 to 87000000
MOE: allocated 112 KByte for the page array @0x8005d000
MOE: virtual user address space [0-bfffffff]
MOE: rom name space cap -> [C:501000]

2012/6/12 Tobias Fink <tobias.fink at stud.h-da.de>:
> Hi Björn,
> that helps to understand it a lot yes. The background of this is, that
> I want to show what low level communication possibilities there would
> be for two instances of l4linux for example without having to use
> sockets or similar technologies. If this would be in principle
> possible due to the fact that everything is a thread, then the example
> that Vasily linked to is enough for me.
> Thank you!
> Tobi
> 2012/6/12 Björn Döbel <doebel at os.inf.tu-dresden.de>:
>> On 12.06.2012 14:41, Tobias Fink wrote:
>>> Hi,
>>> I'm planning on building a small example of a producer/consumer build
>>> on top of L4Re. From the documentation I know about the shared memory
>>> inteface which will help to pass information from the producer to the
>>> consumer but I am a bit clueless on how I notify the consumer that
>>> there is something new to read. The semaphore is only to be used in
>>> between threads so there is no way to use them for IPC between Tasks?!
>>> Is there another possibility to make this work other than to use
>>> polling?
>> There is no communication between tasks, because tasks in terms of L4 /
>> Fiasco.OC are only address spaces (plus some other state, such as the
>> capability index table). The units of execution are always threads and
>> hence communication always happens between those. Does that help you?
>> Bjoern
>> --
>> Dipl.-Inf. Bjoern Doebel    Mail:  doebel at tudos.org
>> TU Dresden, OS Chair        Phone: +49 351 463 38 799
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