Re: tasklets vs. workqueues

[George Anzinger <george@mvista.com>]

Martin Diehl wrote:
> On Wed, 25 Feb 2004, George Anzinger wrote:
> 
> 
>>>>Being in process context, you can also change the priority and schedule policy 
>>>>as needed to fit your application, while you are rather stuck with tasklets in 
>>>>this regard.
>>>
>>>
>>>How would one do that correctly? Something like
>>
>>Depends on where you want to be when you do it.  From user land you would do 
>>exactly what the attached program does.  In SMP you would, likely, want to do 
>>all the tasks in the work queue (one per cpu).
> 
> 
> Ok, thanks - primary concern was kernelthread anyway. Sorry if I wasn't 
> clear enough.
> 
> 
>> From the kernel, again calling setscheduler() is the way to go.  I am not sure 
>>what is in the community tree just now, but if I recall properly, the scheduler 
>>itself does this so, one should be able to copy that code.
>>
>>Ah, yes, there it is in  migration_thread().  It calls setscheduler().
> 
> 
> Basically yes. Except that setscheduler is static in kernel/sched.c so one 
> has to use sys_sched_setscheduler (and add some EXPORT_SYMBOL for it). And 
> of course it needs the set_fs(KERNEL_DS) magic.

I don't think it needs the set_fs(KERNEL_DS) magic if you use the internal 
setscheduler().  If it is static, that should be changed.... as well as the 
EXPORT  sigh.
-g
> 
> Thanks, I was hoping I've missed some simple "official" entry point there 
> to create a SCHED_FIFO kernel thread from a module.
> 
> Martin
> 
> 

-- 
George Anzinger   george@mvista.com
High-res-timers:  http://sourceforge.net/projects/high-res-timers/
Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml