mi_switch(): clean up switch types and their usage
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Authored by mhorne on Jan 24 2023, 9:51 PM.

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jhb
kib
markj

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rG1029dab63457: mi_switch(): clean up switch types and their usage

Summary

Overall, this is a non-functional change, except for kernels built with
SCHED_STATS. However, the switch types are useful for communicating the
intent of the caller.

Ensure that every caller provides a type. In most cases, we upgrade the basic yield to sched_relinquish() aka SWT_RELINQUISH.
The case of sched_bind() is distinct, so add a new switch type SWT_BIND.
Remove the two unused types, SWT_PREEMPT and SWT_SLEEPQTIMO.
Remove SWT_NONE altogether and assert that callers always provide a type flag.
Reference the mi_switch(9) man page in the comments, as these flags will be documented there.

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rG FreeBSD src repository

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Event Timeline

mhorne created this revision.Jan 24 2023, 9:51 PM

Herald added a subscriber: imp. · View Herald TranscriptJan 24 2023, 9:51 PM

mhorne requested review of this revision.Jan 24 2023, 9:51 PM

Harbormaster completed remote builds in B49213: Diff 115561.Jan 24 2023, 9:51 PM

mhorne added a parent revision: D38183: sched_4bsd: use the same switch flags as ULE.Jan 24 2023, 9:51 PM

mhorne added a child revision: D38185: mi_switch(9): update to current day.

markj accepted this revision.Jan 24 2023, 10:06 PM

This revision is now accepted and ready to land.Jan 24 2023, 10:06 PM

kib accepted this revision.Jan 25 2023, 2:10 AM

Expand the scope of the change. Modify callers that don't currently specify a switch reason, and forbid it going forward. Add SWT_BIND for sched_bind(), which IMO is distinct from existing cases.

This revision now requires review to proceed.Jan 30 2023, 7:28 PM

Harbormaster completed remote builds in B49337: Diff 116064.Jan 30 2023, 7:28 PM

mhorne retitled this revision from mi_switch: trim unused type flags to mi_switch(): clean up switch types and their usage.Jan 30 2023, 7:29 PM

mhorne edited the summary of this revision. (Show Details)

mhorne added inline comments.

sys/kern/kern_switch.c
87–88	FYI this does mean we have an unused slot at index zero.

markj accepted this revision.Jan 30 2023, 8:17 PM

markj added inline comments.

sys/kern/kern_switch.c
87–88	Not the end of the world, really. If it's really important we could subtract one when selecting the counter. Another minor cleanup might be to make these an array of counter(9) instead. We didn't have that facility when these counters were added.

This revision is now accepted and ready to land.Jan 30 2023, 8:17 PM

kib accepted this revision.Jan 30 2023, 11:20 PM

Closed by commit rG1029dab63457: mi_switch(): clean up switch types and their usage (authored by mhorne). · Explain WhyFeb 9 2023, 4:03 PM

This revision was automatically updated to reflect the committed changes.

mhorne added a commit: rG1029dab63457: mi_switch(): clean up switch types and their usage.

I just pushed a change to lua loader, but got a compile error message back from ci:

usr/src/sys/kern/kern_poll.c:568:4: error: call to undeclared function 'sched_relinquish'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]

sched_relinquish(td);

and git log -S sched_relinquish pointed me here...

In D38184#875473, @imp wrote:
I just pushed a change to lua loader, but got a compile error message back from ci:

usr/src/sys/kern/kern_poll.c:568:4: error: call to undeclared function 'sched_relinquish'; ISO C99 and later do not support implicit function declarations [-Werror,-Wimplicit-function-declaration]
sched_relinquish(td);
and git log -S sched_relinquish pointed me here...

Thanks, should be fixed by rG78919798e79e.