Re: Swap

[Remco Post <r.post@sara.nl>]

> Christopher Friesen wrote:
> > 
> > "Richard B. Johnson" wrote:
> > >
> > > On Tue, 20 Nov 2001, Wolfgang Rohdewald wrote:
> > >
> > > > On Tuesday 20 November 2001 15:51, J.A. Magallon wrote:
> > > > > When a page is deleted for one executable (because we can re-read it from
> > > > > on-disk binary), it is discarded, not paged out.
> > > >
> > > > What happens if the on-disk binary has changed since loading the program?
> > > > -
> > >
> > > It can't. That's the reason for `install` and other methods of changing
> > > execututable files (mv exe-file exe-file.old ; cp newfile exe-file).
> > > The currently open, and possibly mapped file can be re-named, but it
> > > can't be overwritten.
> > 
> > Actually, with NFS (and probably others) it can.  Suppose I change the file on
> > the server, and it's swapped out on a client that has it mounted.  When it swaps
> > back in, it can get the new information.
> > 
> 
> This sounds really dangerous... What about shared libraries ??
> 

Same problem. This is why most Unix distros tell you to reboot after each 
patch applied and each OS upgrade. just to be sure that all mmapped files and 
page-demand loaded bins are all restarted.


-- 
Met vriendelijke groeten,

Remco Post

SARA - Stichting Academisch Rekencentrum Amsterdam
High Performance Computing  Tel. +31 20 592 8008    Fax. +31 20 668 3167

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