[EMAIL PROTECTED] wrote:
>
> Hi,
> I have read all the old messages on shared memory and nothing has
> helped.
>
> I have been attempting to use shared memory as is spelled out in the
> paper
> "Using Shared Memory in Real-Time Linux" by Fredrick M. Proctor and in
> your
> "HOWTO." I am confused and if you have any suggestions I'd appreciate
> it.
>
> 1. I have gotten shared memory to work with two non-real time
> applications. But, when I try and add a rt application the real-time
> application appears to be accessing different memory because if I write
> a new value to the shared memory the applications don't see it. I have
> verified that the pointer to memory in the real-time application and the
> pointers in the linux applications all contain the same address. I did
> this by passing the rt_ptr through a FIFO to the non-real time
> application and doing an fprintf.
>
> what I mean is that the user_ptr = (BLOCK *) mmap ( .... ) from the
> linux applications is the same as the address pointer in the real-time
> application char *rt_ptr = ADDRESS
Should it be the same ? I mean you map it in the processes memory map.
It is up to mmap where it places the mapped area. (unless you force
it to mmap it at a special place)
Which gives me a problem cause than you can't use datastructures
with pointers in the shared memory. Does anybody know a sollution to
this?
>
> So, why aren't the accessing the same memory?? user_ptr = 0x7d00000 and
> rt_ptr = 0x7d00000 but why doesn't the application see it when the rt
> process initializes the block structure to a value ?? i.e.
> rt_ptr->block[0]= 500 or rt_ptr->block[10] = 444;
>
> I use a common header file where
>
> struct {
> unsigned short block[5000];
> } BLOCK;
>
> Any suggestions ??
>
> I am using Kernel 2.0.36 and RTL v1.1
> I have 128Mbytes of memory on a pentinum II and I want to use close to
> 4Bytes maximum eventually, so my lilo.conf has append="mem=125m"
>
> I am very new to Linux so would appreciate any help in finding the
> answer.
>
> Thanks
>
> Janet Estabridis
> Electrical Engineer
> NAWC Code 473E00D
> China Lake, CA 93555
> (760) 939-2896 FAX (760) 939 -3075
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Erwin Rol (Software Engineer) phone: +49-89-68050051
[EMAIL PROTECTED] fax : +49-89-68050052
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