This change fixes a bug where signal_latency_async_test would flake less
than 1/1000 of the time. What was happening was pthread_kill(sender_thr)
would return EFAULT. This was because pthread_create() was not returning
the thread object pointer until after clone() had been called. So it was
actually possible for the main thread to stall after calling clone() and
during that time the receiver would launch and receive a signal from the
sender thread, and then fail when it tried to send a pong. I thought I'd
use a barrier at first, in the test, to synchronize thread creation, but
I firmly believe that pthread_create() was to blame and now that's fixed
Function trace logs will report stack usage accurately. It won't include
the argv/environ block. Our clone() polyfill is now simpler and does not
use as much stack memory. Function call tracing on x86 is now faster too
This change fixes a bug where gcc assumed thread synchronization such as
pthread_cond_wait() wouldn't alter static variables, because the headers
were using __attribute__((__leaf__)) inappropriately.
This change adds tests for the new memory manager code particularly with
its windows support. Function call tracing now works reliably on Silicon
since our function hooker was missing new Apple self-modifying code APIs
Many tests that were disabled a long time ago on aarch64 are reactivated
by this change, now that arm support is on equal terms with x86. There's
been a lot of places where ftrace could cause deadlocks, which have been
hunted down across all platforms thanks to new tests. A bug in Windows's
kill() function has been identified.
This change makes fork() go nearly as fast as sys_fork() on UNIX. As for
Windows this change shaves about 4-5ms off fork() + wait() latency. This
is accomplished by using WriteProcessMemory() from the parent process to
setup the address space of a suspended process; it is better than a pipe
This change fixes a bug where nsync waiter objects would leak. It'd mean
that long-running programs like runitd would run out of file descriptors
on NetBSD where waiter objects have ksem file descriptors. On other OSes
this bug is mostly harmless since the worst that can happen with a futex
is to leak a little bit of ram. The bug was caused because tib_nsync was
sneaking back in after the finalization code had cleared it. This change
refactors the thread exiting code to handle nsync teardown appropriately
and in making this change I found another issue, which is that user code
which is buggy, and tries to exit without joining joinable threads which
haven't been detached, would result in a deadlock. That doesn't sound so
bad, except the main thread is a joinable thread. So this deadlock would
be triggered in ways that put libc at fault. So we now auto-join threads
and libc will log a warning to --strace when that happens for any thread
On Windows, mmap() now chooses addresses transactionally. It reduces the
risk of badness when interacting with the WIN32 memory manager. We don't
throw darts anymore. There is also no more retry limit, since we recover
from mystery maps more gracefully. The subroutine for combining adjacent
maps has been rewritten for clarity. The print maps subroutine is better
This change goes to great lengths to perfect the stack overflow code. On
Windows you can now longjmp() out of a crash signal handler. Guard pages
previously weren't being restored properly by the signal handler. That's
fixed, so on Windows you can now handle a stack overflow multiple times.
Great thought has been put into selecting the perfect SIGSTKSZ constants
so you can save sigaltstack() memory. You can now use kprintf() with 512
bytes of stack available. The guard pages beneath the main stack are now
recorded in the memory manager.
This change fixes getcontext() so it works right with the %rax register.
This change doubles the performance of thread spawning. That's thanks to
our new stack manager, which allows us to avoid zeroing stacks. It gives
us 15µs spawns rather than 30µs spawns on Linux. Also, pthread_exit() is
faster now, since it doesn't need to acquire the pthread GIL. On NetBSD,
that helps us avoid allocating too many semaphores. Even if that happens
we're now able to survive semaphores running out and even memory running
out, when allocating *NSYNC waiter objects. I found a lot more rare bugs
in the POSIX threads runtime that could cause things to crash, if you've
got dozens of threads all spawning and joining dozens of threads. I want
cosmo to be world class production worthy for 2025 so happy holidays all
This change introduces a new deadlock detector for Cosmo's POSIX threads
implementation. Error check mutexes will now track a DAG of nested locks
and report EDEADLK when a deadlock is theoretically possible. These will
occur rarely, but it's important for production hardening your code. You
don't even need to change your mutexes to use the POSIX error check mode
because `cosmocc -mdbg` will enable error checking on mutexes by default
globally. When cycles are found, an error message showing your demangled
symbols describing the strongly connected component are printed and then
the SIGTRAP is raised, which means you'll also get a backtrace if you're
using ShowCrashReports() too. This new error checker is so low-level and
so pure that it's able to verify the relationships of every libc runtime
lock, including those locks upon which the mutex implementation depends.
It's now possible with cosmo and redbean, to deliver a signal to a child
process after it has called execve(). However the executed program needs
to be compiled using cosmocc. The cosmo runtime WinMain() implementation
now intercepts a _COSMO_PID environment variable that's set by execve().
It ensures the child process will use the same C:\ProgramData\cosmo\sigs
file, which is where kill() will place the delivered signal. We are able
to do this on Windows even better than NetBSD, which has a bug with this
Fixes#1334
Cosmo now has a non-nsync implementation of POSIX read-write locks. It's
possible to call pthread_rwlockattr_setpshared in PTHREAD_PROCESS_SHARED
mode. Furthermore, if cosmo is built with PTHREAD_USE_NSYNC set to zero,
then Cosmo shouldn't use nsync at all. That's helpful if you want to not
link any Apache 2.0 licensed code.
In the course of playing with redbean I was confused about how the state
was behaving and then noticed that some stuff is maybe getting edited by
multiple processes. I tried to improve things by changing the definition
of the counter variables to be explicitly atomic. Claude assures me that
most modern Unixes support cross-process atomics, so I just went with it
on that front.
I also added some mutexes to the shared state to try to synchronize some
other things that might get written or read from workers but couldn't be
made atomic, mainly the rusage and time values. I could've probably been
less granular and just had a global shared-state lock, but I opted to be
fairly granular as a starting point.
This also reorders the resetting of the lastmeltdown timespec before the
SIGUSR2 signal is sent; hopefully this is okay.
American Fuzzy Lop didn't need to try very hard, to crash our privileged
__demangle() implementation. This change helps ensure our barebones impl
will fail rather than crash when given adversarial input data.
