Re: Tasklet usage?

[Neil Horman]

Pierre Ossman wrote:
> Neil Horman wrote:
>
> > Pierre Ossman wrote:
>
>
> > > * Can tasklets be preempted?
> >
> >
> > A tasklet can get preempted by a hard interrupt, but tasklets run in 
> > interrupt context, so don't do anything in a tasklet that can call 
> > schedule.
>
>
> Being preempted by hard interrupts is sort of the point of moving the 
> stuff to a tasklet. Just as long as other tasklets and user space cannot 
> preempt it.
>
> Are there any concerns when it comes to locking and tasklets? I've tried 
> finding kernel-locking-HOWTO referenced in kernel-docs.txt but the link 
> is dead and I can't find a mirror.
Locking in tasklets needs to be done the same way locking in interrupt 
handlers is done.  The only caveat that I can think of is that in the 
event that you are accessing data shared with code that runs outisde of 
the tasklet, you probably need to use spin_lock_bh to disable softirqs 
in the latter code.  In your environment, it would typically replace the 
use of spin_lock_irq[save|restore].

HTH
Neil

> Rgds
> Pierre


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 *Neil Horman
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 *Red Hat, Inc.
 *nhorman@xxxxxxxxxx
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