Yeah, looks like 10.14 and iOS 12. I actually hadn't realized it was so new. Before that, it seems that priority inheritance ("promotion") had long existed for kernel-internal locks [1], but not for anything in userland. It also seems that the behavior of supporting but ignoring PTHREAD_PRIO_INHERIT long predates turnstiles, which is pretty annoying.
As for origins... xnu's implementation appears to be written from scratch, but in terms of inspiration for the design and name, I'm not sure. Aside from Solaris, another possibility is FreeBSD [2] (but note that xnu's turnstiles are in the Mach side of the codebase rather than the BSD side).
[1] https://opensource.apple.com/source/xnu/xnu-1504.15.3/osfmk/...
[2] https://github.com/freebsd/freebsd/commits/master/sys/sys/tu...
In Threads can infect each other with their low priorityfreebsd
freebsd-src
C2012–2026
freebsd / freebsd-src
freebsd-src
The FreeBSD src tree publish-only repository. Experimenting with 'simple' pull requests....
122Distinct people
189Mentions
1Explicit recommenders
9.5KGitHub stars
What to know before exploring
What it is
The FreeBSD src tree publish-only repository. Experimenting with 'simple' pull requests....
GitHub
Where it is used
No documented product use was verified in the last source check.
What people are saying
My favorite piece of man trivia is from the source of the tunefs BSD man page, which contains: .\" Take this out and a Unix Daemon will dog your steps from now until .\" the…
beej71 used a recommendation phrase. One indexed comment matches. This is a phrase match, not a verdict.
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Also in these discussions
- openbsd/src · linked in 7 of the same discussions
- coreutils/coreutils · linked in 3 of the same discussions
- torvalds/linux · linked in 3 of the same discussions
Mentioned in the same Hacker News threads. That is not proof they are substitutes.
This week on Hacker News
Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 10:56:20 AM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year189 dated mentions
Observed mentions: 2012-05-14 23:44:07 UTC to 2026-10-26 20:08:28 UTC.
* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2012 | 2012-01-01 00:00:00 UTC | 2013-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2013 | 2013-01-01 00:00:00 UTC | 2014-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2014 | 2014-01-01 00:00:00 UTC | 2015-01-01 00:00:00 UTC | 7 | 0 | 7 |
| 2015 | 2015-01-01 00:00:00 UTC | 2016-01-01 00:00:00 UTC | 8 | 0 | 8 |
| 2016 | 2016-01-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 4 | 0 | 4 |
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 16 | 1 | 15 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 17 | 0 | 17 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 14 | 1 | 13 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 28 | 2 | 26 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 20 | 1 | 19 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 24 | 0 | 24 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 23 | 0 | 23 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 10 | 2 | 8 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 10 | 1 | 9 |
| 2026 (partial) | 2026-01-01 00:00:00 UTC | 2027-01-01 00:00:00 UTC | 5 | 0 | 5 |
From the project README
An excerpt from the repository, fetched Nov 13, 2026.
Read the project’s introduction
FreeBSD Source:
This is the top level of the FreeBSD source directory.
FreeBSD is an operating system used to power modern servers, desktops, and embedded platforms.
A large community has continually developed it for more than thirty years.
Its advanced networking, security, and storage features have made FreeBSD the platform of choice for many of the busiest web sites and most pervasive embedded networking and storage devices.
For copyright information, please see the file COPYRIGHT in this directory.
Additional copyright information also exists for some sources in this tree - please see the specific source directories for more information.
The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree.
See build(7), config(8), FreeBSD handbook on building userland, and Handbook for kernels for more information, including setting make(1) variables.
For information on the CPU architectures and platforms supported by FreeBSD, see the FreeBSD
website's Platforms page.
For official FreeBSD bootable images, see the release page.
Source Roadmap:
Directory
Description
bin
System/user commands.
cddl
Source code for third-party software under the Common Development and Distribution License.
contrib
Source code for third-party software.
crypto
Source code for cryptographic libraries and commands (see crypto/README).
etc
Template files for /etc.
include
System include files.
kerberos5
Build system for Kerberos 5 (Heimdal).
krb5
Build system for Kerberos 5 (MIT).
lib
System libraries.
libexec
System commands intended to be executed by other commands or daemons.
packages
Base system packages.
release
Makefiles and scripts used for building releases and VM images.
rescue
Build system for statically linked /rescue commands.
sbin
System commands.
secure
Build system for cryptographic libraries and commands (excluding Kerberos).
share
Shared resources.
stand
Boot loader sources.
sys
Kernel sources (see sys/README.md).
targets
Support for experimental DIRDEPS_BUILD
tests
Tests which can be run by Kyua. See tests/README for additional information.
tools
Ancillary utilities and tests (not included in the build).
usr.bin
User commands.
usr.sbin
System administration commands.
For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see FreeBSD Handbook.
Read the full README on GitHubWhat Hacker News says
14 sourcesPort the NetBSD Kcsan Runtime to FreeBSDc
1 points · Open discussionThanks, I finally understood what you are saying.
I am sorry for the unclear comments. I'll stop commenting on a phone ;).
Indeed, the code uses iswspace to test all characters, wide or normal. Strange design choice.
I agree, it's really strange. This seems to be inherited by the FreeBSD version, which still does that as well:
https://github.com/freebsd/freebsd/blob/8f9d69492c3da3a8c1ea...
It has the worst of both worlds: it incorrectly counts the number of words when there is non-ASCII whitespace (since mbrtowc is not used), but it pays the penalty of using iswspace. It's also not in correspondence with POSIX, which states:
The wc utility shall consider a word to be a non-zero-length string of characters delimited by white space.
[...]
C_CTYPE
Determine the locale for the interpretation of sequences of bytes of text data as characters (f
Read the rest
or example, single-byte as opposed to multi-byte characters in arguments and input files) and which characters are defined as white space characters.
This seems more like personal preferences than any sort of standard. For instance:
> Do not use a typedef to hide a pointer or avoid writing “struct”.
Untagged structures:
typedef struct { ... } my_struct_t;
are pretty standard practice in C. In my case, I don't even use tagged structs unless the struct is self-referential:
typedef struct __my_struct_t {
struct __my_struct_t* link;
} my_struct_t;
And some examples in the Linux Source:
https://github.com/torvalds/linux/blob/9331b6740f86163908de6...
https://github.com/torvalds/linux/blob/6cdc577a18a616c331f57...
And FreeBSD:
https://github.com/freebsd/freebsd/blob/0ee2302122d0710ced1e...
In Principles for C Programminghttp://releases.llvm.org/9.0.0/docs/ReleaseNotes.html#notewo...:
”The optimizer will now convert calls to memcmp into a calls to bcmp in some circumstances. Users who are building freestanding code (not depending on the platform’s libc) without specifying -ffreestanding may need to either pass -fno-builtin-bcmp, or provide a bcmp* function.”*
So, he’s, you may have to provide it yourself. I expect you can fairly easily copy-paste it from various BSD-licensed libraries, though (example: https://github.com/freebsd/freebsd/blob/master/sys/libkern/b..., but be warned about that “I don't believe this is a problem since AFAIK, objects are not protected at smaller than longword boundaries”. That likely is, but may not be true on your platform)
In LLVM 9.0Same as /etc/rc. (From which are obviously derived: /etc/rc.local, /etc/rc.d, etc.)
FreeBSD init(8) still refers to it as "runcom":
https://github.com/freebsd/freebsd/blob/90b1841/sbin/init/in...
https://github.com/freebsd/freebsd/blob/90b1841/sbin/init/pa...
In Run Commands, the 'rc' in '.bashrc'And here's the OpenBSD pledge(2) patch for bzip2, for comparison. But similarly it already prevents a compromised bzip2 process from accessing the network, executing arbitrary commands, etc. And when used in a pipeline, accessing the filesystem. This port might actually be a great candidate for unveil(2), if anyone wants to help send a patch. :-)
https://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/ports/a...
And as is typical for FreeBSD, ~7/8 years later these "practical" Capsicum changes were never merged into FreeBSD. :-(
https://github.com/freebsd/freebsd/tree/master/contrib/bzip2
In Capsicum: Practical Capabilities for UnixFreeBSD also imports RCs, for example
https://github.com/freebsd/freebsd/commit/48cf3d0825d200d26e...
Who cares about "really™ final releases"? :D
In OpenMandriva, the first Clang-built Linux distributionSurvey says, in the past ~20 years..
https://github.com/freebsd/freebsd/search?q=MAP_NOCORE&unsco...
Pretty much bupkis. But still more than Capsicum!
In OpenBSD Recent Security Innovationswl_list seems like an incomplete re-implementation of the LIST_ macros in <sys/queue.h>.
http://man7.org/linux/man-pages/man3/queue.3.html
https://github.com/freebsd/freebsd/blob/master/sys/sys/queue...
In C Macro MagicHere's the code from FreeBSD: https://github.com/freebsd/freebsd/blob/master/sys/sys/queue...
In C Macro MagicFreeBSD has had different semantics here for ~20 years: https://github.com/freebsd/freebsd/commit/e4e8fec98ae986357c...
I wish I could find the discussion around that commit.
It'll only start throwing away dirty buffers if the device actually goes away: https://github.com/freebsd/freebsd/commit/46b5afe7b1ae0ee655...
In Linux Fsync Issue for Buffered IO and Its Preliminary Fix for PostgreSQLThe most important part IMHO is here https://github.com/freebsd/freebsd/tree/master/sys/netinet/t.... The TLS sendfile piece is a bit specialized, mainly interesting if you are doing the exact same workload i.e. a CDN on UFS disks. I can say on some authority (I had all the relevant code at my last job) NF will give it to you if you ask and have a need/competence. The reason the TLS bits aren't upstream is that they aren't general purpose or "finished" yet. It relies on some third party code outside of src like boringssl and Intel's isa-l.
In Netflix and FreeBSD: Using Open Source to Deliver Streaming Video [pdf]I think gcc is still in base, right? They just added clang and set that as the default, AFAIK. I haven't kept up with FreeBSD much in the last few years, so not sure what the plans are to remove gcc.
Also, a quick look at the source tree shows there are still some other parts as well. GNU binutils, GNU diff, dialog is GPL, etc. See: https://github.com/freebsd/freebsd/tree/master/contrib
In the kernel, I think there are some drivers that are based on the Linux GPL code, for example: https://github.com/freebsd/freebsd/blob/1d6e4247415d264485ee... (just first hit from GitHub search for "gpl")
So yeah, looks like there's still plenty of GPL code in FreeBSD that's not trivially replaceable. The same applies to OpenBSD, although in general the OpenBSD people tend to be a bit more proactive in replacing GPL code.
In Bash 5.0 released