Re: [Hdaps-devel] Re: HDAPS, Need to park the head for real

[Jens Axboe <axboe@suse.de>]

On Fri, Aug 19 2005, Jon Escombe wrote:
> 
> >>>>Please make it "echo 1 > frozen", then userspace can do "echo 0 > 
> >>>>frozen"
> >>>>after five seconds.
> >>>>       
> >>>>
> >>>What if the code to do "echo 0 > frozen" is swapped out to disk? ;)
> >>>     
> >>>
> >>Emergency head parker needs to be pagelocked for other reasons. You do
> >>not want to page it from disk while your notebook is in free fall.
> >>   
> >>
> >
> >It's still a very bad idea imho, what if the head parker daemon is
> >killed for other reasons? The automatic timeout thawing the drive is
> >much saner.
> > 
> >
> For hard disk protection, I prefer the idea of the userspace code 
> thawing the drive based on current accelerometer data, rather than 
> simply waking up after x seconds (maybe you're running for a bus rather 
> than falling off a table)...
> 
> To get the best of both worlds, could we maybe take a watchdog timer 
> approach, and have the timeout reset by the userspace component 
> periodically re-requesting freeze?

That would work, you can just define the semantics to be that echo
foo > frozen would add foo seconds to the timeout (or thaw it, if foo is
0).

-- 
Jens Axboe