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Differential D21015

sbuf(9): Add NOWAIT dynamic buffer extension mode
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Authored by cem on Jul 21 2019, 5:17 PM.
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vangyzen
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manpages
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rG819999651131: sbuf(9): Add NOWAIT dynamic buffer extension mode
rS350691: sbuf(9): Add NOWAIT dynamic buffer extension mode
Summary

The goal is to avoid some kinds of low-memory deadlock when formatting
buffers.

Test Plan

This reconciles one of the few semantic gaps between our in-house sbuf clone
and sbuf(9).

Diff Detail

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Build Status
Buildable 25448
Build 24073: arc lint + arc unit

Event Timeline

cem created this revision.Jul 21 2019, 5:17 PM
Harbormaster completed remote builds in B25444: Diff 59991.Jul 21 2019, 5:18 PM
cem updated this revision to Diff 59992.Jul 21 2019, 6:25 PM

Need to M_NOWAIT the allocation in sbuf_newbuf for this use case as well.

Harbormaster completed remote builds in B25445: Diff 59992.Jul 21 2019, 6:25 PM
vangyzen added inline comments.Jul 21 2019, 8:28 PM
share/man/man9/sbuf.9
46

Oops.

sys/kern/subr_sbuf.c
240

Why do we ignore SBUF_NOWAIT in flags here? (Was this just for testing?)

cem added a comment.Jul 21 2019, 8:52 PM

Thanks!

share/man/man9/sbuf.9
46

vim-o, will fix

sys/kern/subr_sbuf.c
240

This one is actually constructing the struct sbuf itself. I don't see much value in a heap version of that one that gracefully handles OOM, but I don't feel strongly about it. If you'd prefer it for consistency, I'm happy to use the flag here as well.

cem updated this revision to Diff 60002.Jul 22 2019, 12:09 AM
cem marked an inline comment as done.

Fix the typo in sbuf.9

Harbormaster completed remote builds in B25448: Diff 60002.Jul 22 2019, 12:09 AM
vangyzen added inline comments.Jul 22 2019, 12:32 AM
sys/kern/subr_sbuf.c
240

I agree that it doesn’t seem useful, but I think it’s best to be consistent. If the caller passes NOWAIT, blocking in malloc would be astonishing behavior.

cem updated this revision to Diff 60003.Jul 22 2019, 1:33 AM
cem marked 2 inline comments as done.

Extend use of NOWAIT flag to initial heap sbuf allocation.

Harbormaster completed remote builds in B25449: Diff 60003.Jul 22 2019, 1:34 AM
vangyzen accepted this revision.Jul 22 2019, 1:41 AM
This revision is now accepted and ready to land.Jul 22 2019, 1:41 AM
cem added a child revision: D21029: sbuf(9): Refactor sbuf_newbuf into sbuf_new.Jul 22 2019, 4:54 PM
Closed by commit rS350691: sbuf(9): Add NOWAIT dynamic buffer extension mode (authored by cem). · Explain WhyAug 7 2019, 7:23 PM
This revision was automatically updated to reflect the committed changes.
cem added a commit: rS350691: sbuf(9): Add NOWAIT dynamic buffer extension mode.
Herald added a reviewer: manpages. · View Herald TranscriptAug 7 2019, 7:23 PM
Herald added a subscriber: imp. · View Herald Transcript
imp added a commit: rG819999651131: sbuf(9): Add NOWAIT dynamic buffer extension mode.Jul 16 2021, 5:47 PM

Revision Contents
Changeset List

PathSize
share/
man/
man9/
7 lines
sys/
kern/
16 lines
sys/
1 line

Diff 60002

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share/man/man9/sbuf.9

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sys/kern/subr_sbuf.c

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sys/sys/sbuf.h

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