Re: 指鹸 : where does vmlist be initiated?

[Neil Booth <NeilB@earthling.net>]

Wang Yong wrote:-
> 
> struct vm_struct * get_vm_area(unsigned long size)
> {
> ...
>  for (p = &vmlist; (tmp = *p) ; p = &tmp->next) {
>   if (size + addr < (unsigned long) tmp->addr)
> ...
>  }
> }

[SNIP]

> i think these three functions will not be able to work if vmlist is null. do
> you think so?

They must work as Linux boots.  The key is in the snippet I've kept above.
The test in

for (p = &vmlist; (tmp = *p) ; p = &tmp->next) {

is probably more clearly written as

(tmp = *p) != 0

which fails when vmlist is initially zero, so the loop never executes.
Note p does not hold the value of vmlist, but the address of vmlist.

vmlist is then initialised by the 

*p = area;

that comes a few lines later.

Neil.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://humbolt.geo.uu.nl/Linux-MM/