support `require` in non-main Ractors

Many libraries should be loaded on the main ractor because of
setting constants with unshareable objects and so on.

This patch allows to call `requore` on non-main Ractors by
asking the main ractor to call `require` on it. The calling ractor
waits for the result of `require` from the main ractor.

If the `require` call failed with some reasons, an exception
objects will be deliverred from the main ractor to the calling ractor
if it is copy-able.

Same on `require_relative` and `require` by `autoload`.

Now `Ractor.new{pp obj}` works well (the first call of `pp` requires
`pp` library implicitly).

[Feature #20627]

bootstraptest/test_ractor.rb

@@ -211,17 +211,6 @@ assert_equal '[:a, :b, :c, :d, :e, :f, :g]', %q{
   Ractor.make_shareable(closure).call
 }
 
-# Now autoload in non-main Ractor is not supported
-assert_equal 'ok', %q{
-  autoload :Foo, 'foo.rb'
-  r = Ractor.new do
-    p Foo
-  rescue Ractor::UnsafeError
-    :ok
-  end
-  r.take
-}
-
 ###
 ###
 # Ractor still has several memory corruption so skip huge number of tests
@@ -1836,3 +1825,80 @@ assert_equal 'true', %q{
   shareable = Ractor.make_shareable("chilled")
   shareable == "chilled" && Ractor.shareable?(shareable)
 }
+
+# require in Ractor
+assert_equal 'true', %q{
+  Module.new do
+    def require feature
+      return Ractor._require(feature) unless Ractor.main?
+      super
+    end
+    Object.prepend self
+    set_temporary_name 'Ractor#require'
+  end
+
+  Ractor.new{
+    require 'benchmark'
+    Benchmark.measure{}
+  }.take.real > 0
+}
+
+# require_relative in Ractor
+assert_equal 'true', %q{
+  dummyfile = File.join(__dir__, "dummy#{rand}.rb")
+  return true if File.exist?(dummyfile)
+
+  begin
+    File.write dummyfile, ''
+  rescue Exception
+    # skip on any errors
+    return true
+  end
+
+  begin
+    Ractor.new dummyfile do |f|
+      require_relative File.basename(f)
+    end.take
+  ensure
+    File.unlink dummyfile
+  end
+}
+
+# require_relative in Ractor
+assert_equal 'LoadError', %q{
+  dummyfile = File.join(__dir__, "not_existed_dummy#{rand}.rb")
+  return true if File.exist?(dummyfile)
+
+  Ractor.new dummyfile do |f|
+    begin
+      require_relative File.basename(f)
+    rescue LoadError => e
+      e.class
+    end
+  end.take
+}
+
+# autolaod in Ractor
+assert_equal 'true', %q{
+  autoload :Benchmark, 'benchmark'
+
+  r = Ractor.new do
+    Benchmark.measure{}
+  end
+  r.take.real > 0
+}
+
+# failed in autolaod in Ractor
+assert_equal 'LoadError', %q{
+  dummyfile = File.join(__dir__, "not_existed_dummy#{rand}.rb")
+  autoload :Benchmark, dummyfile
+
+  r = Ractor.new do
+    begin
+      Benchmark.measure{}
+    rescue LoadError => e
+      e.class
+    end
+  end
+  r.take
+}

load.c

@@ -18,6 +18,7 @@
 #include "darray.h"
 #include "ruby/encoding.h"
 #include "ruby/util.h"
+#include "ractor_core.h"
 
 static VALUE ruby_dln_libmap;
 
@@ -1383,17 +1384,25 @@ static VALUE
 rb_require_string_internal(VALUE fname, bool resurrect)
 {
     rb_execution_context_t *ec = GET_EC();
-    int result = require_internal(ec, fname, 1, RTEST(ruby_verbose));
 
-    if (result > TAG_RETURN) {
-        EC_JUMP_TAG(ec, result);
-    }
-    if (result < 0) {
+    // main ractor check
+    if (!rb_ractor_main_p()) {
         if (resurrect) fname = rb_str_resurrect(fname);
-        load_failed(fname);
+        return rb_ractor_require(fname);
     }
+    else {
+        int result = require_internal(ec, fname, 1, RTEST(ruby_verbose));
 
-    return RBOOL(result);
+        if (result > TAG_RETURN) {
+            EC_JUMP_TAG(ec, result);
+        }
+        if (result < 0) {
+            if (resurrect) fname = rb_str_resurrect(fname);
+            load_failed(fname);
+        }
+
+        return RBOOL(result);
+    }
 }
 
 VALUE

ractor.c

@@ -1956,6 +1956,7 @@ cancel_single_ractor_mode(void)
     }
 
     ruby_single_main_ractor = NULL;
+    rb_funcall(rb_cRactor, rb_intern("_activated"), 0);
 }
 
 static void
@@ -2136,6 +2137,13 @@ ractor_create(rb_execution_context_t *ec, VALUE self, VALUE loc, VALUE name, VAL
     return rv;
 }
 
+static VALUE
+ractor_create_func(VALUE klass, VALUE loc, VALUE name, VALUE args, rb_block_call_func_t func)
+{
+    VALUE block = rb_proc_new(func, Qnil);
+    return ractor_create(rb_current_ec_noinline(), klass, loc, name, args, block);
+}
+
 static void
 ractor_yield_atexit(rb_execution_context_t *ec, rb_ractor_t *cr, VALUE v, bool exc)
 {
@@ -2665,6 +2673,8 @@ Init_Ractor(void)
     rb_define_method(rb_cRactorMovedObject, "instance_eval", ractor_moved_missing, -1);
     rb_define_method(rb_cRactorMovedObject, "instance_exec", ractor_moved_missing, -1);
 
+    // internal
+
 #if USE_RACTOR_SELECTOR
     rb_init_ractor_selector();
 #endif
@@ -3869,4 +3879,242 @@ ractor_local_value_set(rb_execution_context_t *ec, VALUE self, VALUE sym, VALUE
     return val;
 }
 
+// Ractor::Channel (emulate with Ractor)
+
+typedef rb_ractor_t rb_ractor_channel_t;
+
+static VALUE
+ractor_channel_func(RB_BLOCK_CALL_FUNC_ARGLIST(y, c))
+{
+    rb_execution_context_t *ec = GET_EC();
+    rb_ractor_t *cr = rb_ec_ractor_ptr(ec);
+
+    while (1) {
+        int state;
+
+        EC_PUSH_TAG(ec);
+        if ((state = EC_EXEC_TAG()) == TAG_NONE) {
+            VALUE obj = ractor_receive(ec, cr);
+            ractor_yield(ec, cr, obj, Qfalse);
+        }
+        EC_POP_TAG();
+
+        if (state) {
+            // ignore the error
+            break;
+        }
+    }
+
+    return Qnil;
+}
+
+static VALUE
+rb_ractor_channel_new(void)
+{
+#if 0
+    return rb_funcall(rb_const_get(rb_cRactor, rb_intern("Channel")), rb_intern("new"), 0);
+#else
+    // class Channel
+    //   def self.new
+    //     Ractor.new do # func body
+    //       while true
+    //         obj = Ractor.receive
+    //         Ractor.yield obj
+    //       end
+    //     rescue Ractor::ClosedError
+    //       nil
+    //     end
+    //   end
+    // end
+
+    return ractor_create_func(rb_cRactor, Qnil, rb_str_new2("Ractor/channel"), rb_ary_new(), ractor_channel_func);
+#endif
+}
+
+static VALUE
+rb_ractor_channel_yield(rb_execution_context_t *ec, VALUE vch, VALUE obj)
+{
+    VM_ASSERT(ec == rb_current_ec_noinline());
+    rb_ractor_channel_t *ch = RACTOR_PTR(vch);
+
+    ractor_send(ec, (rb_ractor_t *)ch, obj, Qfalse);
+    return Qnil;
+}
+
+static VALUE
+rb_ractor_channel_take(rb_execution_context_t *ec, VALUE vch)
+{
+    VM_ASSERT(ec == rb_current_ec_noinline());
+    rb_ractor_channel_t *ch = RACTOR_PTR(vch);
+
+    return ractor_take(ec, (rb_ractor_t *)ch);
+}
+
+static VALUE
+rb_ractor_channel_close(rb_execution_context_t *ec, VALUE vch)
+{
+    VM_ASSERT(ec == rb_current_ec_noinline());
+    rb_ractor_channel_t *ch = RACTOR_PTR(vch);
+
+    ractor_close_incoming(ec, (rb_ractor_t *)ch);
+    return ractor_close_outgoing(ec, (rb_ractor_t *)ch);
+}
+
+// Ractor#require
+
+struct cross_ractor_require {
+    VALUE ch;
+    VALUE result;
+    VALUE exception;
+
+    // require
+    VALUE feature;
+
+    // autoload
+    VALUE module;
+    ID name;
+};
+
+static VALUE
+require_body(VALUE data)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+
+    ID require;
+    CONST_ID(require, "require");
+    crr->result = rb_funcallv(Qnil, require, 1, &crr->feature);
+
+    return Qnil;
+}
+
+static VALUE
+require_rescue(VALUE data, VALUE errinfo)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+    crr->exception = errinfo;
+    return Qundef;
+}
+
+static VALUE
+require_result_copy_body(VALUE data)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+
+    if (crr->exception != Qundef) {
+        VM_ASSERT(crr->result == Qundef);
+        crr->exception = ractor_copy(crr->exception);
+    }
+    else{
+        VM_ASSERT(crr->result != Qundef);
+        crr->result = ractor_copy(crr->result);
+    }
+
+    return Qnil;
+}
+
+static VALUE
+require_result_copy_resuce(VALUE data, VALUE errinfo)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+    crr->exception = errinfo; // ractor_move(crr->exception);
+    return Qnil;
+}
+
+static VALUE
+ractor_require_protect(struct cross_ractor_require *crr, VALUE (*func)(VALUE))
+{
+    // catch any error
+    rb_rescue2(func, (VALUE)crr,
+               require_rescue, (VALUE)crr, rb_eException, 0);
+
+    rb_rescue2(require_result_copy_body, (VALUE)crr,
+               require_result_copy_resuce, (VALUE)crr, rb_eException, 0);
+
+    rb_ractor_channel_yield(GET_EC(), crr->ch, Qtrue);
+    return Qnil;
+
+}
+
+static VALUE
+ractore_require_func(void *data)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+    return ractor_require_protect(crr, require_body);
+}
+
+VALUE
+rb_ractor_require(VALUE feature)
+{
+    // TODO: make feature shareable
+    struct cross_ractor_require crr = {
+        .feature = feature, // TODO: ractor
+        .ch = rb_ractor_channel_new(),
+        .result = Qundef,
+        .exception = Qundef,
+    };
+
+    rb_execution_context_t *ec = GET_EC();
+    rb_ractor_t *main_r = GET_VM()->ractor.main_ractor;
+    rb_ractor_interrupt_exec(main_r, ractore_require_func, &crr, 0);
+
+    // wait for require done
+    rb_ractor_channel_take(ec, crr.ch);
+    rb_ractor_channel_close(ec, crr.ch);
+
+    if (crr.exception != Qundef) {
+        rb_exc_raise(crr.exception);
+    }
+    else {
+        return crr.result;
+    }
+}
+
+static VALUE
+ractor_require(rb_execution_context_t *ec, VALUE self, VALUE feature)
+{
+    return rb_ractor_require(feature);
+}
+
+static VALUE
+autoload_load_body(VALUE data)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+    crr->result = rb_autoload_load(crr->module, crr->name);
+    return Qnil;
+}
+
+static VALUE
+ractor_autoload_load_func(void *data)
+{
+    struct cross_ractor_require *crr = (struct cross_ractor_require *)data;
+    return ractor_require_protect(crr, autoload_load_body);
+}
+
+VALUE
+rb_ractor_autoload_load(VALUE module, ID name)
+{
+    struct cross_ractor_require crr = {
+        .module = module,
+        .name = name,
+        .ch = rb_ractor_channel_new(),
+        .result = Qundef,
+        .exception = Qundef,
+    };
+
+    rb_execution_context_t *ec = GET_EC();
+    rb_ractor_t *main_r = GET_VM()->ractor.main_ractor;
+    rb_ractor_interrupt_exec(main_r, ractor_autoload_load_func, &crr, 0);
+
+    // wait for require done
+    rb_ractor_channel_take(ec, crr.ch);
+    rb_ractor_channel_close(ec, crr.ch);
+
+    if (crr.exception != Qundef) {
+        rb_exc_raise(crr.exception);
+    }
+    else {
+        return crr.result;
+    }
+}
+
 #include "ractor.rbinc"

ractor.rb

@@ -835,11 +835,13 @@ class Ractor
   end
 
   # get a value from ractor-local storage of current Ractor
+  # Obsolete and use Ractor.[] instead.
   def [](sym)
     Primitive.ractor_local_value(sym)
   end
 
   # set a value in ractor-local storage of current Ractor
+  # Obsolete and use Ractor.[]= instead.
   def []=(sym, val)
     Primitive.ractor_local_value_set(sym, val)
   end
@@ -867,4 +869,32 @@ class Ractor
       GET_VM()->ractor.main_ractor == rb_ec_ractor_ptr(ec)
     }
   end
+
+  # internal method
+  def self._require feature
+    if main?
+      super feature
+    else
+      Primitive.ractor_require feature
+    end
+  end
+
+  class << self
+    private
+
+    # internal method that is called when the first "Ractor.new" is called
+    def _activated
+      Kernel.prepend Module.new{|m|
+        m.set_temporary_name '<RactorRequire>'
+
+        def require feature
+          if Ractor.main?
+            super
+          else
+            Ractor._require feature
+          end
+        end
+      }
+    end
+  end
 end

ractor_core.h

@@ -222,6 +222,8 @@ void rb_ractor_terminate_interrupt_main_thread(rb_ractor_t *r);
 void rb_ractor_terminate_all(void);
 bool rb_ractor_main_p_(void);
 void rb_ractor_atfork(rb_vm_t *vm, rb_thread_t *th);
+VALUE rb_ractor_require(VALUE feature);
+VALUE rb_ractor_autoload_load(VALUE space, ID id);
 
 VALUE rb_ractor_ensure_shareable(VALUE obj, VALUE name);
 

thread_pthread.c

@@ -845,7 +845,7 @@ thread_sched_wait_running_turn(struct rb_thread_sched *sched, rb_thread_t *th, b
     RUBY_DEBUG_LOG("th:%u", rb_th_serial(th));
 
     ASSERT_thread_sched_locked(sched, th);
-    VM_ASSERT(th == GET_THREAD());
+    VM_ASSERT(th == rb_ec_thread_ptr(rb_current_ec_noinline()));
 
     if (th != sched->running) {
         // already deleted from running threads
@@ -900,12 +900,12 @@ thread_sched_wait_running_turn(struct rb_thread_sched *sched, rb_thread_t *th, b
                     thread_sched_set_lock_owner(sched, th);
                 }
 
-                VM_ASSERT(GET_EC() == th->ec);
+                VM_ASSERT(rb_current_ec_noinline() == th->ec);
             }
         }
 
         VM_ASSERT(th->nt != NULL);
-        VM_ASSERT(GET_EC() == th->ec);
+        VM_ASSERT(rb_current_ec_noinline() == th->ec);
         VM_ASSERT(th->sched.waiting_reason.flags == thread_sched_waiting_none);
 
         // add th to running threads

thread_pthread.h

@@ -132,7 +132,6 @@ struct rb_thread_sched {
 
 #ifdef RB_THREAD_LOCAL_SPECIFIER
   NOINLINE(void rb_current_ec_set(struct rb_execution_context_struct *));
-  NOINLINE(struct rb_execution_context_struct *rb_current_ec_noinline(void));
 
   # ifdef __APPLE__
     // on Darwin, TLS can not be accessed across .so

variable.c

@@ -2994,7 +2994,7 @@ rb_autoload_load(VALUE module, ID name)
 
     // At this point, we assume there might be autoloading, so fail if it's ractor:
     if (UNLIKELY(!rb_ractor_main_p())) {
-        rb_raise(rb_eRactorUnsafeError, "require by autoload on non-main Ractor is not supported (%s)", rb_id2name(name));
+        return rb_ractor_autoload_load(module, name);
     }
 
     // This state is stored on the stack and is used during the autoload process.

vm.c

@@ -556,7 +556,7 @@ RB_THREAD_LOCAL_SPECIFIER rb_execution_context_t *ruby_current_ec;
 RB_THREAD_LOCAL_SPECIFIER rb_atomic_t ruby_nt_serial;
 #endif
 
-// no-inline decl on thread_pthread.h
+// no-inline decl on vm_core.h
 rb_execution_context_t *
 rb_current_ec_noinline(void)
 {
@@ -580,6 +580,14 @@ rb_current_ec(void)
 #endif
 #else
 native_tls_key_t ruby_current_ec_key;
+
+// no-inline decl on vm_core.h
+rb_execution_context_t *
+rb_current_ec_noinline(void)
+{
+    return native_tls_get(ruby_current_ec_key);
+}
+
 #endif
 
 rb_event_flag_t ruby_vm_event_flags;

vm_core.h

@@ -1969,6 +1969,8 @@ rb_ec_vm_ptr(const rb_execution_context_t *ec)
     }
 }
 
+NOINLINE(struct rb_execution_context_struct *rb_current_ec_noinline(void));
+
 static inline rb_execution_context_t *
 rb_current_execution_context(bool expect_ec)
 {