Re: your mail

[Jens Axboe]

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