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

[Manfred Spraul]

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