Re: per-thread global variables

["J.A. Magallon" <jamagallon@able.es>]

On 2002.07.12 Alan Cox wrote:
>> about an __attribute(( )) in gcc. Other solutions imply a search based
>> on pid, but I would like to find some more direct method.
>> Something like using the PRDA in IRIX.
>
>If your stacks are the same size you can do the kernel trick with stack
>maths to hide thread globals. 
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>

Uhm, something like reserving X bytes for stack, and telling clone()
I pass it a X-sizeof(prda) stack ?

How do I get the stack start from inside a thread ?

BTW, isn't there a barrier() syscall in Linux ? I could implement it 
with a semaphore with -N holes, but...man sem_init

       tially to value.  The pshared argument  indicates  whether
       the semaphore is local to the current process ( pshared is
       zero) or is to  be  shared  between  several  processes  (
       pshared is not zero). LinuxThreads currently does not sup­
       port  process-shared  semaphores,  thus  sem_init   always
       returns with error ENOSYS if pshared is not zero.


TIA

-- 
J.A. Magallon             \   Software is like sex: It's better when it's free
mailto:jamagallon@able.es  \                    -- Linus Torvalds, FSF T-shirt
Linux werewolf 2.4.19-rc1-jam3, Mandrake Linux 8.3 (Cooker) for i586
gcc (GCC) 3.1.1 (Mandrake Linux 8.3 3.1.1-0.7mdk)