Re: 2.2.1{3,4,5pre*} VM bug found

[Rik van Riel <riel@nl.linux.org>]

On Tue, 25 Jan 2000, Andrea Arcangeli wrote:

> Before calling schedule() you always gets registered in a
> waitqueue so you can't deadlock or wait too much.
> 
> If something there is the opposite problem. If you do:
> 
> 	__set_current_state(TASK_UNINTERRUPTIBLE);
> 	get_page(GFP_KERNEL);
> 	XXXXXXXXXXXXXXXXXXXX
> 	schedule();
> 
> then at point XXXXXXX you may become a task running and you don't
> block anymore.

The problem in this case is that schedule() may be called
from within get_page(GFP_KERNEL). This already was possible
in 2.2.14 and before (if the task had to wait for I/O on
try_to_free_pages()), but the explicit schedule() in my
stuff in 2.2.15pre4 amplified the problem and made it
visible.

A fix for this problem is in one of my other emails and
at my web page:  http://www.surriel.com/patches/

regards,

Rik
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