Re: [PATCH 5/5 v0.6] sched/umcg: add Documentation/userspace-api/umcg.txt

Hi Thierry,

sorry for the delayed reply - I'm finally going through the
documentation patches in preparation for the upcoming next version
patchset mail-out.

No problem.

The documentation here outlines what sys_umcg_wait does, and it does
put the current task to sleep without context switching if next_tid is
zero. The question of whether this behavior is or is not appropriate
for a worker wishing to yield/park itself is at a "policy" level, if
you wish, and this "policy" level is described in "state transitions"
section later in the document. sys_umcg_wait() does not enforce this
"policy" directly, in order to make it simpler and easier to describe
and reason about.

Just to be clear, sys_umcg_wait supports an operation that, when called from
a worker, puts the worker to sleep without triggering block detection
or context-switching back to the server?

quoted

With that said, I'm a little confused by the usage of "yields" in that
example. I would expect workers yielding to behave like kernel threads
calling sched_yield(), i.e., context switch to the server but also be
immediately added to the idle_workers_ptr.

I'm not a fan of arguing about how to name things. If the maintainers
ask me to rename wait/wake to park/unpark, I'll do that.

I understand the sentiment, and I'm perfectly happy with the use of wait/wake.
I was exclusively referring to this one use of "yield" in the documentation.