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SubjectRe: Scheduling tasklets from process context...
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    arun> Since tasklets are typically used for bottom half
arun> processing, is it acceptable/recommended that they be
arun> scheduled from a process context (say an ioctl handler)?

arun> Should one try to minimize such scheduling and try to do
arun> things in process context if possible, as tasklets run in
arun> interrupt context? Or is the driver writer free to use the
arun> tasklets at will? What is recommended here?

I guess it would work to schedule a tasklet from your ioctl handler, but
I don't see a good reason to do it. What are you really trying to do?

Your ioctl handler runs in process context so you are free to do
pretty much anything -- allocate with GFP_KERNEL, sleep, etc. If you
want to return to userspace immediately but defer some work until
later, it would probably make more sense to use something like
schedule_work() instead of a tasklet.

The main point of tasklets is that they run at a high priority, very
soon after they're scheduled, so that an interrupt handler can return
quickly by deferring work to a tasklet but still not add too much
latency. But in your ioctl handler, if you have some high priority
work, you can just do it immediately without the complication of a tasklet.

- R.

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