Re: filecache/swapcache questions [RFC] [RFT] [PATCH] kanoj-mm12-2.3.8 Fix swapoff races

[kanoj@google.engr.sgi.com (Kanoj Sarcar)]

> 
> Hi,
> 
> On Mon, 28 Jun 1999 14:11:18 -0700 (PDT), kanoj@google.engr.sgi.com
> (Kanoj Sarcar) said:
> 
> > If I understand right, here is an example. Lets say I believe I 
> > have scanned uptil pid 10. You are suggesting, after having scanned
> > pid 10, hold on to task_lock, and look for the min pid > 10. Say
> > that is pid 12. Problem is, while I was scanning pid 10, maybe
> > pid 5 got reallocated, and pid 5 is a new process (probably a 
> > child of pid 20). 
> 
> Fine --- repeat the whole thing until we have no swap entries left.  We
> can still guarantee to make progress without extra locking for normal
> swapping. 
>

This will almost always work, except theoretically, you still can
not guarantee forward progress, unless you can stop forks() from
happening. That is, given a high enough rate of forking, swapoff
is never going to terminate. 

Kanoj
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