Recursive mutexes now go as fast as normal mutexes. The tradeoff is they
are no longer safe to use in signal handlers. However you can still have
signal safe mutexes if you set your mutex to both recursive and pshared.
You can also make functions that use recursive mutexes signal safe using
sigprocmask to ensure recursion doesn't happen due to any signal handler
The impact of this change is that, on Windows, many functions which edit
the file descriptor table rely on recursive mutexes, e.g. open(). If you
develop your app so it uses pread() and pwrite() then your app should go
very fast when performing a heavily multithreaded and contended workload
For example, when scaling to 40+ cores, *NSYNC mutexes can go as much as
1000x faster (in CPU time) than the naive recursive lock implementation.
Now recursive will use *NSYNC under the hood when it's possible to do so
The worst issue I had with consts.sh for clock_gettime is how it defined
too many clocks. So I looked into these clocks all day to figure out how
how they overlap in functionality. I discovered counter-intuitive things
such as how CLOCK_MONOTONIC should be CLOCK_UPTIME on MacOS and BSD, and
that CLOCK_BOOTTIME should be CLOCK_MONOTONIC on MacOS / BSD. Windows 10
also has some incredible new APIs, that let us simplify clock_gettime().
- Linux CLOCK_REALTIME -> GetSystemTimePreciseAsFileTime()
- Linux CLOCK_MONOTONIC -> QueryUnbiasedInterruptTimePrecise()
- Linux CLOCK_MONOTONIC_RAW -> QueryUnbiasedInterruptTimePrecise()
- Linux CLOCK_REALTIME_COARSE -> GetSystemTimeAsFileTime()
- Linux CLOCK_MONOTONIC_COARSE -> QueryUnbiasedInterruptTime()
- Linux CLOCK_BOOTTIME -> QueryInterruptTimePrecise()
Documentation on the clock crew has been added to clock_gettime() in the
docstring and in redbean's documentation too. You can read that to learn
interesting facts about eight essential clocks that survived this purge.
This is original research you will not find on Google, OpenAI, or Claude
I've tested this change by porting *NSYNC to become fully clock agnostic
since it has extensive tests for spotting irregularities in time. I have
also included these tests in the default build so they no longer need to
be run manually. Both CLOCK_REALTIME and CLOCK_MONOTONIC are good across
the entire amd64 and arm64 test fleets.
At least in neovim, `│vi:` is not recognized as a modeline because it
has no preceding whitespace. After fixing this, opening a file yields
an error because `net` is not an option. (`noet`, however, is.)
The *NSYNC linked list API is good enough that it deserves to be part of
the C libray, so this change writes an improved version of it which uses
that offsetof() trick from the Linux Kernel. We vendor all of the *NSYNC
tests in third_party which helped confirm the needed refactoring is safe
This change also deletes more old code that didn't pan out. My goal here
is to work towards a vision where the Cosmopolitan core libraries become
less experimental and more focused on curation. This better reflects the
current level of quality we've managed to achieve.
- Clean up sigaction() code
- Add a port scanner example
- Introduce a ParseCidr() API
- Clean up our futex abstraction code
- Fix a harmless integer overflow in ParseIp()
- Use kernel semaphores on NetBSD to make threads much faster
