Search the list archive for more info about using shared memory.
You may need the vremap() call in your RT-Linux module:
shmem = (SHMEM_ST *)vremap(SHMEM_BASE_ADDRESS,sizeof(SHMEM_ST));
Followed later by:
//clean-up shared memory
vfree(shmem);
-Don
On Thu, 17 Jun 1999, Olaf Petzold wrote:
> Hallo,
>
> I'm using shared memory described in
> <http://www.isd.cme.nist.gov/projects/emc/shmem.html>
> "Using Shared Memory in Real-Time Linux" from Frederick M. Proctor.
> I expanded the structures for using data like this inside
> common.h:
> ...
> typedef struct
> {
> unsigned int inuse;
> int arg1;
> double arg2;
> double LUT[4096]; /* my LoockUpTable for DAU */
> } MY_DATA;
> ...
> typedef struct
> {
> MY_COMMAND cmd;
> MY_DATA data;
> MY_STATUS status;
> MY_ERROR error;
> } MY_STRUCT;
> ...
>
> inside rt_process.c I wrote:
>
> static void task_code(int t)
> {
> ...
> for (;;)
> {
> ...
>
>
> my_struct.status.heartbeat++;
>
> /* DAQ - Only for fun at moment */
> my_struct.data.arg1=0;
> my_struct.data.arg2=0.0;
>
> /* write data to shmem */
> if (0 == my_struct_ptr->data.inuse)
> memcpy(&my_struct_ptr->data,
> &my_struct.data,
> sizeof(MY_DATA));
>
> ...
> rt_task_wait();
> }
> }
>
> with the result, my system is frozen for a long time
> (mostly a hard reset was following..) while insmod rtmod
>
> # time insmod rtmod.o && rmmod rtmod && echo DONE
> real 0m0.010s
> user 0m0.010s
> sys 0m0.000s
> DONE
>
> This is was time says. What is wrong with this code?
> or is there another/better/faster way? Without this
> structure data all things are fine.
>
> Olaf
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> ----
> For more information on Real-Time Linux see:
> http://www.rtlinux.org/~rtlinux/
>
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