Looks like the infamous cache aliasing problem.  Steve Longerbeam had a patch 
which may help.  Please try it and let me know the results.

Thanks.

Jun


Maurice Turcotte wrote:

> Greetings:
> 
> I am having a problem with Linux Kernel 2.4.5 on a mips.
> 
> I have two processes using share memory for IPC. This same
> code works fine with Kernel 2.4.7 on a x86. The problem is 
> that the second process reads old data out of the shared
> memory.
> 
> The executive summary->
> 
> Process #1 writes "A" to shared memory at 0x2aac7210
> Process #2 reads 0 from shared memory at address 0x2aaca210
> Process #1 writes "B" to shared memory at 0x2aac7210
> Process #2 read "A" from shared memory at address 0x2aaca210
> Process #1 writes "C" to shared memory at 0x2aac7210
> Process #2 read "B" from shared memory at address 0x2aaca210
> 
> It is interesting that the processes get different addresses
> associated with the same shmId. I assume this is because of 
> some user-space mapping that is going on.
> 
> I left out the semaphore diddling, but I believe that part of
> the code is correct because it works flawlessly on the 2.4.7 x86.
> 
> Any tips on debugging this would be greatly appreciated. If this
> is not the proper forum for questions like this, please point me
> in the right direction.
> 
> Thanks,
> 
> mturc
> 
>