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SubjectRe: [patch] Remove tq_scheduler
On Sat, 18 Nov 2000, Andrew Morton wrote:

>
> This patch removes tq_scheduler from the kernel. All uses of
> tq_scheduler are migrated over to use schedule_task().
>
> Notes:
> - If anyone sleeps in a callback, then all other users of
> schedule_task() also sleep. But there's nothing new here. Kinda
> makes one wonder why schedule_task exists. But what-hey, it's neat.

Because you're only supposed to use it if the task that is scheduled:
A) Doesn't care about a reasonable delay
B) Doesn't sleep for an unreasonable amount of time.

As long as there's some value of 'reasonable' to match the set of tasks
which you are using schedule_task() for at any given moment, you should be
fine.

If it's really necessary in 2.5, we can consider using multiple queues to
get round this problem - either a task per subsystem or a pool of worker
threads. Hopefully it won't be necessary though. We'll see.

> - Note the careful massaging of module reference counts.
>
> Yes my friends, much usage of task queues in modules is racy wrt
> module removal. This patch fixes some of them.

Cool. I was going to look into that. I had figured we should fix it
completely or not at all, though, which is why I didn't do the trick with
use counts. I probably should have done, though.

While you're in maintenance mode, do you feel like fixing up stuff to use
up_and_exit() for killing kernel threads? I started on net/sunrpc/sched.c
but it made my head hurt so I gave up and started hacking PCMCIA
instead :)

Also, drivers/usb/hub.c can probably use schedule_task() now instead of
its own kernel thread.

--
dwmw2


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