Retain reference to blocking fibers.

doc/hacking.md

@@ -1,16 +1,12 @@
 # Ruby Hacking Guide
 
-This document gives  some helpful instructions which  should make your
-experience as a Ruby core developer easier.
+This document gives some helpful instructions which should make your experience as a Ruby core developer easier.
 
 ## Setup
 
 ### Make
 
-It's common to want to compile things as quickly as possible. Ensuring
-`make`  has the  right `--jobs`  flag will  ensure all  processors are
-utilized when building  software projects To do  this effectively, you
-can set `MAKEFLAGS` in your shell configuration/profile:
+It's common to want to compile things as quickly as possible. Ensuring `make` has the right `--jobs` flag will ensure all processors are utilized when building software projects To do this effectively, you can set `MAKEFLAGS` in your shell configuration/profile:
 
 ``` shell
 # On macOS with Fish shell:
@@ -40,8 +36,7 @@ make install
 
 ### Without Documentation
 
-If you  are frequently  building Ruby,  this will  reduce the  time it
-takes to `make install`.
+If you are frequently building Ruby, this will reduce the time it takes to `make install`.
 
 ``` shell
 ../configure --disable-install-doc
@@ -51,15 +46,13 @@ takes to `make install`.
 
 ### Run Local Test Script
 
-You can create  a file in the Ruby source  root called `test.rb`.  You
-can build `miniruby` and execute this script:
+You can create a file in the Ruby source root called `test.rb`. You can build `miniruby` and execute this script:
 
 ``` shell
 make run
 ```
 
-If  you want  more  of the  standard library,  you  can use  `runruby`
-instead of `run`.
+If you want more of the standard library, you can use `runruby` instead of `run`.
 
 ## Running Tests
 
@@ -71,8 +64,7 @@ make check
 
 ### Run Bootstrap Tests
 
-There are  a set of tests  in `bootstraptest/` which cover  most basic
-features of the core Ruby language.
+There are a set of tests in `bootstraptest/` which cover most basic features of the core Ruby language.
 
 ``` shell
 make test
@@ -80,8 +72,7 @@ make test
 
 ### Run Extensive Tests
 
-There  are extensive  tests in  `test/` which  cover a  wide range  of
-features of the Ruby core language.
+There are extensive tests in `test/` which cover a wide range of features of the Ruby core language.
 
 ``` shell
 make test-all
@@ -95,9 +86,7 @@ make test-all TESTS=../test/fiber/test_io.rb
 
 ### Run Ruby Spec Suite Tests
 
-The [Ruby Spec Suite](https://github.com/ruby/spec/) is a test suite
-that aims to provide an executable description for the behavior of the
-language.
+The [Ruby Spec Suite](https://github.com/ruby/spec/) is a test suite that aims to provide an executable description for the behaviour of the language.
 
 ``` shell
 make test-spec
@@ -110,6 +99,8 @@ Using the address sanitizer is a great way to detect memory issues.
 ``` shell
 > ./autogen.sh
 > mkdir build && cd build
-> ../configure cppflags="-fsanitize=address -fno-omit-frame-pointer" optflags=-O1 LDFLAGS="-fsanitize=address -fno-omit-frame-pointer"
->
+> ../configure cppflags="-fsanitize=address -fno-omit-frame-pointer" optflags=-O0 LDFLAGS="-fsanitize=address -fno-omit-frame-pointer"
+> make
 ```
+
+On Linux it is important to specify -O0 when debugging and this is especially true for ASAN which sometimes works incorrectly at higher optimisation levels.

test/fiber/scheduler.rb

@@ -30,7 +30,7 @@ class Scheduler
     @closed = false
 
     @lock = Thread::Mutex.new
-    @blocking = 0
+    @blocking = Hash.new.compare_by_identity
     @ready = []
 
     @urgent = IO.pipe
@@ -57,7 +57,7 @@ class Scheduler
   def run
     # $stderr.puts [__method__, Fiber.current].inspect
 
-    while @readable.any? or @writable.any? or @waiting.any? or @blocking.positive?
+    while @readable.any? or @writable.any? or @waiting.any? or @blocking.any?
       # Can only handle file descriptors up to 1024...
       readable, writable = IO.select(@readable.keys + [@urgent.first], @writable.keys, [], next_timeout)
 
@@ -211,20 +211,22 @@ class Scheduler
   def block(blocker, timeout = nil)
     # $stderr.puts [__method__, blocker, timeout].inspect
 
+    fiber = Fiber.current
+
     if timeout
-      @waiting[Fiber.current] = current_time + timeout
+      @waiting[fiber] = current_time + timeout
       begin
         Fiber.yield
       ensure
         # Remove from @waiting in the case #unblock was called before the timeout expired:
-        @waiting.delete(Fiber.current)
+        @waiting.delete(fiber)
       end
     else
-      @blocking += 1
+      @blocking[fiber] = true
       begin
         Fiber.yield
       ensure
-        @blocking -= 1
+        @blocking.delete(fiber)
       end
     end
   end

test/fiber/test_scheduler.rb

@@ -106,22 +106,24 @@ class TestFiberScheduler < Test::Unit::TestCase
   end
 
   def test_autoload
-    Object.autoload(:TestFiberSchedulerAutoload, File.expand_path("autoload.rb", __dir__))
+    100.times do
+      Object.autoload(:TestFiberSchedulerAutoload, File.expand_path("autoload.rb", __dir__))
 
-    thread = Thread.new do
-      scheduler = Scheduler.new
-      Fiber.set_scheduler scheduler
+      thread = Thread.new do
+        scheduler = Scheduler.new
+        Fiber.set_scheduler scheduler
 
-      10.times do
-        Fiber.schedule do
-          Object.const_get(:TestFiberSchedulerAutoload)
+        10.times do
+          Fiber.schedule do
+            Object.const_get(:TestFiberSchedulerAutoload)
+          end
         end
       end
-    end
 
-    thread.join
-  ensure
-    $LOADED_FEATURES.delete(File.expand_path("autoload.rb", __dir__))
-    Object.send(:remove_const, :TestFiberSchedulerAutoload)
+      thread.join
+    ensure
+      $LOADED_FEATURES.delete(File.expand_path("autoload.rb", __dir__))
+      Object.send(:remove_const, :TestFiberSchedulerAutoload)
+    end
   end
 end

variable.c

@@ -2132,7 +2132,7 @@ struct autoload_const {
     VALUE module;
 
     // The name of the constant we are loading.
-    VALUE name;
+    ID name;
 
     // The value of the constant (after it's loaded).
     VALUE value;
@@ -2308,22 +2308,6 @@ autoload_feature_lookup_or_create(VALUE feature, struct autoload_data **autoload
     return autoload_data_value;
 }
 
-#if 0
-static VALUE
-autoload_feature_clear_if_empty(VALUE argument)
-{
-    RUBY_ASSERT_MUTEX_OWNED(autoload_mutex);
-
-    struct autoload_data *autoload_data = (struct autoload_data *)argument;
-
-    if (ccan_list_empty(&autoload_data->constants)) {
-        rb_hash_delete(autoload_features, autoload_data->feature);
-    }
-
-    return Qnil;
-}
-#endif
-
 static struct st_table *
 autoload_table_lookup_or_create(VALUE module)
 {
@@ -2596,14 +2580,13 @@ autoload_load_needed(VALUE _arguments)
     struct autoload_load_arguments *arguments = (struct autoload_load_arguments*)_arguments;
 
     const char *loading = 0, *src;
-    struct autoload_data *ele;
 
     if (!autoload_defined_p(arguments->module, arguments->name)) {
         return Qfalse;
     }
 
-    VALUE load = check_autoload_required(arguments->module, arguments->name, &loading);
-    if (!load) {
+    VALUE autoload_const_value = check_autoload_required(arguments->module, arguments->name, &loading);
+    if (!autoload_const_value) {
         return Qfalse;
     }
 
@@ -2613,22 +2596,23 @@ autoload_load_needed(VALUE _arguments)
     }
 
     struct autoload_const *autoload_const;
-    if (!(ele = get_autoload_data(load, &autoload_const))) {
+    struct autoload_data *autoload_data;
+    if (!(autoload_data = get_autoload_data(autoload_const_value, &autoload_const))) {
         return Qfalse;
     }
 
-    if (ele->mutex == Qnil) {
-        ele->mutex = rb_mutex_new();
-        ele->fork_gen = GET_VM()->fork_gen;
+    if (autoload_data->mutex == Qnil) {
+        autoload_data->mutex = rb_mutex_new();
+        autoload_data->fork_gen = GET_VM()->fork_gen;
     }
-    else if (rb_mutex_owned_p(ele->mutex)) {
+    else if (rb_mutex_owned_p(autoload_data->mutex)) {
         return Qfalse;
     }
 
+    arguments->mutex = autoload_data->mutex;
     arguments->autoload_const = autoload_const;
-    arguments->mutex = ele->mutex;
 
-    return load;
+    return autoload_const_value;
 }
 
 static VALUE
@@ -2730,17 +2714,17 @@ rb_autoload_load(VALUE module, ID name)
     struct autoload_load_arguments arguments = {.module = module, .name = name, .mutex = Qnil, .result = Qnil};
 
     // Figure out whether we can autoload the named constant:
-    VALUE load = rb_mutex_synchronize(autoload_mutex, autoload_load_needed, (VALUE)&arguments);
+    VALUE autoload_const_value = rb_mutex_synchronize(autoload_mutex, autoload_load_needed, (VALUE)&arguments);
 
     // This confirms whether autoloading is required or not:
-    if (load == Qfalse) return load;
+    if (autoload_const_value == Qfalse) return autoload_const_value;
 
     arguments.flag = ce->flag & (CONST_DEPRECATED | CONST_VISIBILITY_MASK);
 
     // Only one thread will enter here at a time:
-    return rb_mutex_synchronize(arguments.mutex, autoload_try_load, (VALUE)&arguments);
+    VALUE result = rb_mutex_synchronize(arguments.mutex, autoload_try_load, (VALUE)&arguments);
 
-    // rb_mutex_synchronize(autoload_mutex, autoload_feature_clear_if_empty, (VALUE)&arguments.autoload_data);
+    return result;
 }
 
 VALUE