Re: Tasklet usage?

[Neil Horman <nhorman@redhat.com>]

Pierre Ossman wrote:
> My driver needs to spend a lot of time inside the interrupt handler 
> (draining a FIFO). I suspect this might cause problems blocking other 
> interrupt handlers so I was thinking about moving this into a tasklet.
> Not being to familiar with tasklets, a few questions pop up.
> 
> * Will a tasklet scheduled from the interrupt handler be executed as 
> soon as interrupt handling is done?
I don't _think_ they are guaranteed to be executed immediately after the 
  interrupt handler top half is complete, but they will execute before 
the next return to user space (read: they will complete before user 
processes run again).

> * 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.
> * If a tasklet gets scheduled while running, will it be executed once 
> more? (Needed if I get another FIFO interrupt while the tasklet is just 
> exiting).
> 
IIRC, a tasklet will execute once for every time tasklet_schedule is called.

HTH
Neil

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