trouble with shared memory in userland

Paolo Mantegazza mantegazza at aero.polimi.it
Thu Jun 8 08:38:30 CEST 2006


Xudong Guan wrote:
> Hi Bert,
> 
>> Whatever I try in userland, everything I tried returned a NULL pointer.
>> For example the same line as above, but also rtai_malloc and 
>> rtai_kmalloc.
>>
>> Anyone an idea why?
> 
> 
> The device node /dev/rtai_shm must exist for user land share memory
> allocation. The same applies to the fifo nodes /dev/rtf0 etc... I put
> this line before launching the share memory application:
> 
> if test \! -r /dev/rtai_shm; then mknod -m 666 /dev/rtai_shm c 10 254; fi
> 
> This is caused by the devfs or udev features in the new kernel, which
> generate /dev/* dynamically. Everytime you reboot, you need to create
> the node again. For better solutions, google with these keywords:
> 
>   site:mail.rtai.org rtai_shm udev

The item should be solved in magma.

Paolo.





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