From: "jpcamara (JP Camara) via ruby-core" <ruby-core@...>
Date: 2023-12-24T17:47:14+00:00
Subject: [ruby-core:115885] [Ruby master Bug#20076] M:N scheduler is stuck on macOS with RUBY_MN_THREADS=1

Issue #20076 has been updated by jpcamara (JP Camara).


A one-line change fixes it for me, and fixes almost every failure I was seeing when running `test-all` using `RUBY_MN_THREADS=1`. Here is the change: https://github.com/ruby/ruby/pull/9344/files

```c
static ssize_t
rb_io_read_memory(rb_io_t *fptr, void *buf, size_t count)
{
    VALUE scheduler = rb_fiber_scheduler_current();
    if (scheduler != Qnil) {
        VALUE result = rb_fiber_scheduler_io_read_memory(scheduler, fptr->self, buf, count, 0);

        if (!UNDEF_P(result)) {
            return rb_fiber_scheduler_io_result_apply(result);
        }
    }

    struct io_internal_read_struct iis = {
        .th = rb_thread_current(),
        .fptr = fptr,
        .nonblock = 0,
        .fd = fptr->fd,

        .buf = buf,
        .capa = count,
        .timeout = NULL,
    };

    struct timeval timeout_storage;

    if (fptr->timeout != Qnil) {
        timeout_storage = rb_time_interval(fptr->timeout);
        iis.timeout = &timeout_storage;
    }

    // previous line 
    // VVVVVV
    // return (ssize_t)rb_thread_io_blocking_call(internal_read_func, &iis, fptr->fd, RB_WAITFD_IN);
    return (ssize_t)rb_thread_io_blocking_call(internal_read_func, &iis, fptr->fd, RB_WAITFD_IN | RB_WAITFD_OUT);
}
```

There's almost _no way_ that it actually fixes the core issue. It has to be that it causes a fallback to some native 1:1 thread behavior. But it is extremely curious that this single change to `rb_io_read_memory` fixes the issue?

----------------------------------------
Bug #20076: M:N scheduler is stuck on macOS with RUBY_MN_THREADS=1
https://bugs.ruby-lang.org/issues/20076#change-105841

* Author: hsbt (Hiroshi SHIBATA)
* Status: Open
* Priority: Normal
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
This is known issue. I already shared this to ko1.

The version of https://github.com/ruby/ruby/commit/28e3886689c71b22487dd5d0cb62f3b5ed0a77cc is crashed with `make exam`.

This is happend with webrick test on `make test-tool`.

My environment is macOS Sonoma 14.3 beta1 and

```
$ pkgutil --pkg-info=com.apple.pkg.CLTools_Executables
package-id: com.apple.pkg.CLTools_Executables
version: 15.1.0.0.1.1700200546
volume: /
location: /
install-time: 1702331495
```






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