RE: [microblaze-uclinux] pthread_attr_setstack() limitation

[Brettschneider Falk <fbrettschneider@xxxxxxxxxxxxxxxxx>]

Hi,
OK, 0x0 may be a bit all-out. But what is a useful limitation? Here, I saw
about 1KB as peak value.
I think if one uses that special function, he knows what he's doing. Any
limitation might be wrong. And whatever I set on stack creation, I always
can write beyond the stack range.
For myself, I measured the stack usage with a test pattern and tweaked it
afterwards.
    unsigned int*   pCurStackAddr;
    ...
    while (pCheckStackAddr != pCurStackAddr) {
        if (*pCheckStackAddr != 0x5354414B) { // 'STAK'
            pLastUsedStackAddr = pCheckStackAddr; break;
        }
        pCheckStackAddr++;
    }
E.g. I shared the SRAM memory for several threads with different fixed stack
sizes, and the sizes were quite small, but stable, so I can predict its max
value.

CU, F@lk

> -----Original Message-----
> From: owner-microblaze-uclinux@xxxxxxxxxxxxxx
> [mailto:owner-microblaze-uclinux@xxxxxxxxxxxxxx]On Behalf Of John
> Williams
> Sent: Monday, February 27, 2006 11:18 PM
> To: microblaze-uclinux@xxxxxxxxxxxxxx
> Subject: Re: [microblaze-uclinux] pthread_attr_setstack() limitation
> 
> 
> Hi Falk,
> 
> Brettschneider Falk wrote:
> 
> > as I was playing around to use an 8KB SRAM as stack via
> > pthread_attr_setstack() I saw there's a strange stacksize 
> limitation in the
> > pthread lib. I removed that locally, because a global 
> search doesn't show a
> > explanation that makes sense to me. Could it be changed in 
> the official CVS
> > tree as well? See the patch below.
> 
> I might be missing something here, but allowing zero sized 
> stacks sounds
> like a recipe for disaster, particularly on a noMMU system.  The first
> function call or local variable allocation made by a thread will start
> trashing memory.  Whether the limit should be 16kb, or 8kb, or 4, or
> whatever, is debatable, but zero seems like a bad idea?
> 
> Custom stacks setup via pthread_attr_setstack () can be any size you
> like - the library is assuming you know what you are doing in 
> that case.
> 
> John
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