Re: Timer queues: Which one should I use...
Wed, 7 May 1997 18:35:42 +0200

> From: (Alan Cox)
> Subject: Re: Timer queues: Which one should I use...
> To: (Grant R. Guenther)
> Date: Tue, 6 May 1997 23:30:30 +0100 (BST)
> Cc:,

> > David and others have observed that under heavy load a ZIP drive can
> > cause systems to freeze. The ppa adapter doesn't generate an
> Can you not get the thing to give you an interrupt does it not waggle
paper > out or ack or anything useful ?

It waggles ack when the attached device (the disk) is selected which
is not very useful since this is the only pin that will generate
hardware interrupts.

> > so the driver must simulate interrupts using task queues. There are
two > > basic choices: tq_scheduler and tq_timer.
> Or add_timer() a timer of your own.

Can add_timer() do 1000 us call backs??

>> I've since switched to using tq_timer with more stable results but
>> apparently there has been a performance drop. Any suggestions?
>Add it to both queues and take it off the other when it is called ?

Fine except for one minor problem, I can't find a routine to remove a
request once it is on a task queue. Either that or I'm looking at a
very old <linux/tqueue.h>.

David Campbell