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SubjectRe: [PATCH] proposed scheduler enhancements and fixes


On 25 Feb 2000, Dimitris Michailidis wrote:
>
> * adds a new scheduling policy SCHED_IDLE. Processes of this type run on CPUs
> that would otherwise be idle. Useful for apps like SETI@Home, code crackers,
> etc. Implementation of this feature is extremely lightweight.
> Among the scheduling functions only schedule() is SCHED_IDLE-aware
> and the overhead for non-idle CPUs is at most 1 instruction per schedule()
> invocation;

So why do you think your implementation of this doesn't have the deadlock
that every other implementation has?

The deadlock is due to priority inversion, where a "idle-priority" task
gets a resource (say the directory semaphore), goes to sleep, and never
wakes up again because there is some slightly more important process
running all the time.

In short, this has been tried before, and it has ALWAYS been a serious
security holw full of denial-of-service kind of attacks.

Not applied,

Linus


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