Re: [PATCH] Make highly niced processes run only when idle

From: Niteshadow (niteshadow@tulene.sk)
Date: Mon Dec 10 2001 - 07:25:42 EST

On Mon, Dec 10, 2001 at 12:46:23AM -0200, Rik van Riel wrote:
> On 9 Dec 2001, Robert Love wrote:
>
> > Hmm, what if we only boosted it based on something like this:
> >
> > if (p->policy == SCHED_IDLE) {
> > weight = p->counter;
> > if (p->lock_depth >= 0 || signal_pending(p))
> > /* boost somehow ... */
> > }
>
> Now what if the process is holding an inode or superblock
> semaphore ?

Even better:

What if the SCHED_IDLE task holds a POSIX read lock on a file ?

Say we have three processes:
A is SCHED_IDLE holding read lock on /foo/bar
B is SCHED_OTHER wanting to acquire write lock /foo/bar
C is SCHED_OTHER computing fractals and eating up every cycle it can get

What we want is A to get B's priority until it releases the lock on
/foo/bar and then revert it to SCHED_IDLE policy. Otherwise B would get
deadlocked with A while C (or any other CPU hog) is running.

I know this is a userspace problem (similar to real-time processes vs.
normal processes), but I think it would be nice to make SCHED_IDLE
non-priviliged policy. 

-- 
Kind regards,
Robert Varga
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n@hq.sk                                          http://hq.sk/~nite/gpgkey.txt
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