Previously, we created joinable threads.
As a result, all threads would be kept alive after completion so that pthread_join could wait for them.
We never call pthread_join, so threads would never get cleaned up.
Additionally, the thread creation error check was performed after waiting for the thread to start.
If pthread_create failed, the caller would get stuck waiting for a thread that was never created.
Found this bug while trying to use the upstream testing package instead
of our own. The io/fs package wasn't passing, because the test was run
in a separate goroutine (and therefore a separate thread, with its own
stack) instead of all in the same thread with our own stack
creation/switching implementation.
This makes sure system calls like read don't return EINTR but instead
restart the call on an interrupt. This is by far the more sensible
option, the default POSIX behavior of returning EINTR is extremely
error-prone.
Found this bug while trying to use the upstream testing package instead
of our own.
For the threads scheduler, it makes sense to have NumCPU available.
For all other schedulers, the number of available CPUs is practically
limited to one by the scheduler (even though the system might have more
CPUs).
This is not a scheduler in the runtime, instead every goroutine is
mapped to a single OS thread - meaning 1:1 scheduling.
While this may not perform well (or at all) for large numbers of
threads, it greatly simplifies many things in the runtime. For example,
blocking syscalls can be called directly instead of having to use epoll
or similar. Also, we don't need to do anything special to call C code -
the default stack is all we need.
Damian Gryski
Nia Waldvogel
Ayke van Laethem