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Date: Tue, 8 May 2001 22:06:43 +0200
From: Jens Axboe <axboe@suse.de>
To: "Richard B. Johnson" <root@chaos.analogic.com>
Cc: Linux kernel <linux-kernel@vger.kernel.org>
Subject: Re: your mail
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In-Reply-To: <Pine.LNX.3.95.1010508154726.29540A-100000@chaos.analogic.com>; from root@chaos.analogic.com on Tue, May 08, 2001 at 03:48:45PM -0400
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On Tue, May 08 2001, Richard B. Johnson wrote:
> 
> To driver wizards:
> 
> I have a driver which needs to wait for some hardware.
> Basically, it needs to have some code added to the run-queue
> so it can get some CPU time even though it's not being called.
> 
> It needs to get some CPU time which can be "turned on" or
> "turned off" as a result of an interrupt or some external
> input from  an ioctl().
> 
> So I thought that the "tasklet" would be ideal. However, the
> scheduler "thinks" that a tasklet is an interrupt, so any
> attempt to sleep in the tasklet results in a kernel panic,
> "ieee scheduling in an interrupt..., BUG sched.c line 688".

Use a kernel thread? If you don't need to access user space, context
switches are very cheap.

> So, what am I supposed to do to add a piece of driver code to the
> run queue so it gets scheduled occasionally?

Several, grep for kernel_thread.

-- 
Jens Axboe