Re: Q: behaviour of mlockall(MCL_FUTURE) and VM_GROWSDOWN segments

From: Manfred Spraul (manfred@colorfullife.com)
Date: Sat Jan 12 2002 - 11:07:42 EST


Andi Kleen wrote:
>
> For the stack they can get minor faults anyways when they allocate new
> stack space below ESP. There is no good way to fix that from the kernel; the
> application has to preallocate its memory on stack. I think it's reasonable
> if it does the same for holes on the stack.
>
Ok, everyone agrees that mlockall() should not grow VM_GROWSDOWN
segments to their maximum size.
Should the page fault handler fill the hole created by

void * grow_stack(void)
{
        char data[100000];
        data[0] = '0';
        return data;
}

The principle of least surprise would mean filling holes, but OTHO sane
apps would use memset(data,0,sizeof(data)).

--
	Manfred
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