Fix ec assertion with using pthread

[peterzhu2118]

When RUBY_DEBUG is enabled, the following script causes an assertion failure:

Fiber.new(&Object.method(:class_eval)).resume("foo")

The assertion failure is:

Assertion Failed: ractor_core.h:328:rb_ractor_set_current_ec_:ec == ((void*)0) || cr->threads.running_ec != ec

-- C level backtrace information -------------------------------------------
miniruby(rb_vm_bugreport+0xb60) [0x100290f20] vm_dump.c:1151
miniruby(rb_vm_bugreport) (null):0
miniruby(rb_assert_failure_detail+0xa4) [0x1003b533c] error.c:1168
miniruby(rb_assert_failure_detail+0x0) [0x1003b5298] error.c:1148
miniruby(rb_assert_failure) (null):0
miniruby(Init_native_thread.cold.1+0x0) [0x1003d3c24] ractor_core.h:328
miniruby(rb_ractor_set_current_ec_) (null):0
miniruby(ruby_thread_set_native.cold.1) thread_pthread.c:1624
miniruby(Init_native_thread+0x0) [0x100222380] ractor_core.h:328
miniruby(ruby_thread_set_native) (null):0
miniruby(fiber_entry+0x1c) [0x10008a1c4] cont.c:845
miniruby(coroutine_trampoline+0xa8) [0x1003a1d78] coroutine/pthread/Context.c:148
/usr/lib/system/libsystem_pthread.dylib(_pthread_start+0x88) [0x1911fef94]

[ko1]

I couldn't reproduce this issue because of the following error.

$ ./miniruby -v -e 'Fiber.new(&Object.method(:class_eval)).resume("foo")'
ruby 3.4.0dev (2024-04-08T02:13:29Z master 4dd9e5cf74) [x86_64-linux]
-e:in 'Module#class_eval': Can't eval on top of Fiber or Thread (RuntimeError)

Do I missing something?

[ko1]

This assertion represents that nobody set same ec to itself.
If this assertion is wrong, we need to understand why.

[peterzhu2118]

@ko1 I configured with CPPFLAGS=-DRUBY_DEBUG ../configure --with-coroutine=pthread and I ran ./miniruby -v -e 'Fiber.new(&Object.method(:class_eval)).resume("foo")'

And I got:

ruby 3.4.0dev (2024-04-09T13:50:09Z master 0bc71828b5) [arm64-darwin23]
last_commit=[pty] Split `chfunc` into functions in steps
Assertion Failed: ractor_core.h:328:rb_ractor_set_current_ec_:ec == ((void*)0) || cr->threads.running_ec != ec

[peterzhu2118]

It's happening because th->ractor->threads.running_ec == th->ec is true at boot, so calling ruby_thread_set_native again will cause it to have an assertion failure.

I opened #10491 as an alternative.