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Date: Thu, 18 Apr 2024 15:51:36 +0000
From: "Martin Husemann" <martin@netbsd.org>
Subject: CVS commit: [netbsd-9] src
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Module Name:	src
Committed By:	martin
Date:		Thu Apr 18 15:51:36 UTC 2024

Modified Files:
	src/share/man/man9 [netbsd-9]: workqueue.9
	src/sys/kern [netbsd-9]: subr_workqueue.c
	src/tests/rump/kernspace [netbsd-9]: kernspace.h workqueue.c
	src/tests/rump/rumpkern [netbsd-9]: Makefile t_workqueue.c

Log Message:
Pull up following revision(s) (requested by riastradh in ticket #1830):

	sys/kern/subr_workqueue.c: revision 1.40
	sys/kern/subr_workqueue.c: revision 1.41
	sys/kern/subr_workqueue.c: revision 1.42
	sys/kern/subr_workqueue.c: revision 1.43
	sys/kern/subr_workqueue.c: revision 1.44
	sys/kern/subr_workqueue.c: revision 1.45
	sys/kern/subr_workqueue.c: revision 1.46
	tests/rump/kernspace/workqueue.c: revision 1.7
	sys/kern/subr_workqueue.c: revision 1.47
	tests/rump/kernspace/workqueue.c: revision 1.8
	tests/rump/kernspace/workqueue.c: revision 1.9
	tests/rump/rumpkern/t_workqueue.c: revision 1.3
	tests/rump/rumpkern/t_workqueue.c: revision 1.4
	tests/rump/kernspace/kernspace.h: revision 1.9
	tests/rump/rumpkern/Makefile: revision 1.20
	sys/kern/subr_workqueue.c: revision 1.39
	share/man/man9/workqueue.9: revision 1.15
	(all via patch)

workqueue: Lift unnecessary restriction on workqueue_wait.

Allow multiple concurrent waits at a time, and allow enqueueing work
at the same time (as long as it's not the work we're waiting for).

This way multiple users can use a shared global workqueue and safely
wait for individual work items concurrently, while the workqueue is
still in use for other items (e.g., wg(4) peers).

This has the side effect of taking away a diagnostic measure, but I
think allowing the diagnostic's false positives instead of rejecting
them is worth it.  We could cheaply add it back with some false
negatives if it's important.
workqueue(9): workqueue_wait and workqueue_destroy may sleep.

But might not, so assert sleepable up front.
workqueue(9): Sprinkle dtrace probes.
tests/rump/rumpkern: Use PROGDPLIBS, not explicit -L/-l.

This way we relink the t_* test programs whenever changes under
tests/rump/kernspace change libkernspace.a.

workqueue(9) tests: Nix trailing whitespace.

workqueue(9) tests: Destroy struct work immediately on entry.

workqueue(9) tests: Add test for PR kern/57574.

workqueue(9): Avoid touching running work items in workqueue_wait.

As soon as the workqueue function has called, it is forbidden to
touch the struct work passed to it -- the function might free or
reuse the data structure it is embedded in.

So workqueue_wait is forbidden to search the queue for the batch of
running work items.  Instead, use a generation number which is odd
while the thread is processing a batch of work and even when not.
There's still a small optimization available with the struct work
pointer to wait for: if we find the work item in one of the per-CPU
_pending_ queues, then after we wait for a batch of work to complete
on that CPU, we don't need to wait for work on any other CPUs.
PR kern/57574

workqueue(9): Sprinkle dtrace probes for workqueue_wait edge cases.

Let's make it easy to find out whether these are hit.

workqueue(9): Stop violating queue(3) internals.

workqueue(9): Avoid unnecessary mutex_exit/enter cycle each loop.

workqueue(9): Sort includes.
No functional change intended.

workqueue(9): Factor out wq->wq_flags & WQ_FPU in workqueue_worker.
No functional change intended.  Makes it clearer that s is
initialized when used.


To generate a diff of this commit:
cvs rdiff -u -r1.12 -r1.12.6.1 src/share/man/man9/workqueue.9
cvs rdiff -u -r1.37 -r1.37.6.1 src/sys/kern/subr_workqueue.c
cvs rdiff -u -r1.8 -r1.8.2.1 src/tests/rump/kernspace/kernspace.h
cvs rdiff -u -r1.6 -r1.6.8.1 src/tests/rump/kernspace/workqueue.c
cvs rdiff -u -r1.18 -r1.18.2.1 src/tests/rump/rumpkern/Makefile
cvs rdiff -u -r1.2 -r1.2.8.1 src/tests/rump/rumpkern/t_workqueue.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.