gistfile1.c

#include <ruby.h>
#include <ruby/io.h>
#include <unistd.h>
#include <pthread.h>
#include <signal.h>

extern void *rb_thread_call_without_gvl(void *(*func)(void *), void *data1,
         rb_unblock_function_t *ubf, void *data2);
extern void *rb_thread_call_with_gvl(void *(*func)(void *), void *data1);

volatile int halt = 0;

static void *int_func(void *data){
    printf("please unblock: %d\n", ruby_native_thread_p());
    return NULL;
}


static void ubf_func(void *data)
{
    halt = 1;
}

static void* halt_func(void *data)
{
    while(1==1) {
        if(halt) {
            printf("before rb_thread_call_with_gvl\n");
            rb_thread_call_with_gvl(int_func, NULL);
            printf("after rb_thread_call_with_gvl\n");
            halt = 0;
        }
    }
    return NULL;
}

static VALUE
rb_test_halt(VALUE module)
{
    VALUE thread = rb_thread_current();
    rb_thread_call_without_gvl(halt_func, NULL, ubf_func, (void*)thread);
    return Qnil;
}


void Init_test( void )
{
    VALUE rb_mTest = rb_define_module("Test");
    rb_define_module_function(rb_mTest, "halt", rb_test_halt, 0);
}

gistfile2.txt

require 'mkmf'
create_header
create_makefile('test')

`make`

puts Process.pid


$:.unshift(".")
require "test"

Thread.new do
  sleep 1
  # this kills the process but should not ...
  `kill -s USR1 #{Process.pid}`
end

trap :USR1 do
  p "GOT USR1"
end

Test.halt