Add taskqueue_quiesce().
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Authored by markj on Nov 13 2018, 5:40 PM.

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Reviewers

mav
avg
jhb
allanjude
cem

Group Reviewers

manpages

Commits

rS340731: Use taskqueue_quiesce(9) to implement taskq_wait().
rS340730: Add a taskqueue_quiesce(9) KPI.

Summary

This emulates illumos' taskq_wait() in that it doesn't return until the
queue is completely empty. This fixes some races when shutting down
ZFS as described in PR 227784.

Test Plan

wulf@ reports that this fixes the panic reported in PR 227784.

Diff Detail

Repository

rS FreeBSD src repository - subversion

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Event Timeline

markj created this revision.Nov 13 2018, 5:40 PM

Harbormaster completed remote builds in B20790: Diff 50368.Nov 13 2018, 5:40 PM

markj edited the test plan for this revision. (Show Details)Nov 13 2018, 5:41 PM

markj added reviewers: mav, avg, jhb, allanjude.

The code and documentation look good; I'm just not sure if we want a new API for this, or if changing taskqueue_drain_all()'s behavior to match this would be unobjectionable.

This revision is now accepted and ready to land.Nov 15 2018, 5:34 PM

Any thoughts on this approach? To provide a bit more detail, the issue is that some ZFS tasks may recursively enqueue tasks, but a taskqueue_drain_all() doesn't wait for them. It might be that we could just change the behaviour of taskqueue_drain_all() instead.

In D17975#384630, @markj wrote:

Any thoughts on this approach? To provide a bit more detail, the issue is that some ZFS tasks may recursively enqueue tasks, but a taskqueue_drain_all() doesn't wait for them. It might be that we could just change the behaviour of taskqueue_drain_all() instead.

Looks like the LinuxKPI's flush_workqueue() maps to the existing taskqueue_drain_all(), so we probably don't want to change the existing behaviour.

I plan to commit this in the next day or so if there are no objections.

Closed by commit rS340730: Add a taskqueue_quiesce(9) KPI. (authored by markj). · Explain WhyNov 21 2018, 5:18 PM

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