ruby/ruby-2.4.2-IO-close-do-not-enqueue-redundant-interrupts.patch

From 27251312111b7e25e347773e5777ee6072f9289b Mon Sep 17 00:00:00 2001
From: nagachika <nagachika@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 8 Jul 2017 02:21:36 +0000
Subject: [PATCH] merge revision(s) 58284,58812,59028: [Backport #13632]

	vm_core.h: ruby_error_stream_closed

	* vm_core.h (ruby_special_exceptions): renamed
	  ruby_error_closed_stream as ruby_error_stream_closed, like the
	  message.
	speed up IO#close with many threads

	Today, it increases IO#close performance with many threads:

	  Execution time (sec)
	  name            trunk   after
	  vm_thread_close 4.276   3.018

	  Speedup ratio: compare with the result of `trunk' (greater is better)
	  name            after
	  vm_thread_close 1.417

	This speedup comes because rb_notify_fd_close only scans threads
	inside rb_thread_io_blocking_region, not all threads in the VM.

	In the future, this type data structure may allow us to notify
	waiters of multiple FDs on a single thread (when using
	Fibers).

	* thread.c (struct waiting_fd): declare
	  (rb_thread_io_blocking_region): use on-stack list waiter
	  (rb_notify_fd_close): walk vm->waiting_fds instead
	  (call_without_gvl): remove old field setting
	  (th_init): ditto
	* vm_core.h (typedef struct rb_vm_struct): add waiting_fds list
	* (typedef struct rb_thread_struct): remove waiting_fd field
	  (rb_vm_living_threads_init): initialize waiting_fds list

	I am now kicking myself for not thinking about this 3 years ago
	when I introduced ccan/list in [Feature #9632] to optimize this
	same function :<
	IO#close: do not enqueue redundant interrupts (take #2)

	Enqueuing multiple errors for one event causes spurious errors
	down the line, as reported by Nikolay Vashchenko in
	https://bugs.ruby-lang.org/issues/13632

	This should fix bad interactions with test_race_gets_and_close
	in test/ruby/test_io.rb since we ensure rb_notify_fd_close
	continues returning the busy flag after enqueuing the interrupt.

	Backporting changes to 2.4 and earlier releases will be more
	challenging...

	* thread.c (rb_notify_fd_close): do not enqueue multiple interrupts
	  [ruby-core:81581] [Bug #13632]
	* test/ruby/test_io.rb (test_single_exception_on_close):
	  new test based on script from Nikolay

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@59286 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 test/ruby/test_io.rb | 22 ++++++++++++++++++++++
 thread.c             | 36 +++++++++++++++++++++++++-----------
 vm.c                 |  1 -
 vm_core.h            |  6 +++---
 4 files changed, 50 insertions(+), 15 deletions(-)

diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 61dfba318042..034dac570ce4 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -2809,6 +2809,28 @@ def test_cross_thread_close_stdio
     end;
   end
 
+  def test_single_exception_on_close
+    a = []
+    t = []
+    10.times do
+      r, w = IO.pipe
+      a << [r, w]
+      t << Thread.new do
+        while r.gets
+        end rescue IOError
+        Thread.current.pending_interrupt?
+      end
+    end
+    a.each do |r, w|
+      w.write -"\n"
+      w.close
+      r.close
+    end
+    t.each do |th|
+      assert_equal false, th.value, '[ruby-core:81581] [Bug #13632]'
+    end
+  end
+
   def test_open_mode
     feature4742 = "[ruby-core:36338]"
     bug6055 = '[ruby-dev:45268]'
diff --git a/thread.c b/thread.c
index 7391cf96d284..2691fd835de4 100644
--- a/thread.c
+++ b/thread.c
@@ -95,7 +95,11 @@ static int rb_threadptr_pending_interrupt_empty_p(rb_thread_t *th);
 #define eTerminateSignal INT2FIX(1)
 static volatile int system_working = 1;
 
-#define closed_stream_error GET_VM()->special_exceptions[ruby_error_closed_stream]
+struct waiting_fd {
+    struct list_node wfd_node; /* <=> vm.waiting_fds */
+    rb_thread_t *th;
+    int fd;
+};
 
 inline static void
 st_delete_wrap(st_table *table, st_data_t key)
@@ -1310,7 +1314,6 @@ call_without_gvl(void *(*func)(void *), void *data1,
     rb_thread_t *th = GET_THREAD();
     int saved_errno = 0;
 
-    th->waiting_fd = -1;
     if (ubf == RUBY_UBF_IO || ubf == RUBY_UBF_PROCESS) {
 	ubf = ubf_select;
 	data2 = th;
@@ -1433,11 +1436,15 @@ VALUE
 rb_thread_io_blocking_region(rb_blocking_function_t *func, void *data1, int fd)
 {
     volatile VALUE val = Qundef; /* shouldn't be used */
+    rb_vm_t *vm = GET_VM();
     rb_thread_t *th = GET_THREAD();
     volatile int saved_errno = 0;
     int state;
+    struct waiting_fd wfd;
 
-    th->waiting_fd = fd;
+    wfd.fd = fd;
+    wfd.th = th;
+    list_add(&vm->waiting_fds, &wfd.wfd_node);
 
     TH_PUSH_TAG(th);
     if ((state = EXEC_TAG()) == 0) {
@@ -1448,8 +1455,8 @@ rb_thread_io_blocking_region(rb_blocking_function_t *func, void *data1, int fd)
     }
     TH_POP_TAG();
 
-    /* clear waiting_fd anytime */
-    th->waiting_fd = -1;
+    /* must be deleted before jump */
+    list_del(&wfd.wfd_node);
 
     if (state) {
 	TH_JUMP_TAG(th, state);
@@ -2195,16 +2202,23 @@ int
 rb_notify_fd_close(int fd)
 {
     rb_vm_t *vm = GET_THREAD()->vm;
-    rb_thread_t *th = 0;
+    struct waiting_fd *wfd = 0;
     int busy;
 
     busy = 0;
-    list_for_each(&vm->living_threads, th, vmlt_node) {
-	if (th->waiting_fd == fd) {
-	    VALUE err = th->vm->special_exceptions[ruby_error_closed_stream];
+    list_for_each(&vm->waiting_fds, wfd, wfd_node) {
+	if (wfd->fd == fd) {
+	    rb_thread_t *th = wfd->th;
+	    VALUE err;
+
+	    busy = 1;
+	    if (!th) {
+		continue;
+	    }
+	    wfd->th = 0;
+	    err = th->vm->special_exceptions[ruby_error_stream_closed];
 	    rb_threadptr_pending_interrupt_enque(th, err);
 	    rb_threadptr_interrupt(th);
-	    busy = 1;
 	}
     }
     return busy;
@@ -4839,7 +4853,7 @@ Init_Thread(void)
     rb_define_method(rb_cThread, "name=", rb_thread_setname, 1);
     rb_define_method(rb_cThread, "inspect", rb_thread_inspect, 0);
 
-    rb_vm_register_special_exception(ruby_error_closed_stream, rb_eIOError, "stream closed");
+    rb_vm_register_special_exception(ruby_error_stream_closed, rb_eIOError, "stream closed");
 
     cThGroup = rb_define_class("ThreadGroup", rb_cObject);
     rb_define_alloc_func(cThGroup, thgroup_s_alloc);
diff --git a/vm.c b/vm.c
index 0544bcc4e573..c8ed39ad1e47 100644
--- a/vm.c
+++ b/vm.c
@@ -2477,7 +2477,6 @@ th_init(rb_thread_t *th, VALUE self)
     th->status = THREAD_RUNNABLE;
     th->errinfo = Qnil;
     th->last_status = Qnil;
-    th->waiting_fd = -1;
     th->root_svar = Qfalse;
     th->local_storage_recursive_hash = Qnil;
     th->local_storage_recursive_hash_for_trace = Qnil;
diff --git a/vm_core.h b/vm_core.h
index d0385d219f82..8e2b93d8e9b2 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -427,7 +427,7 @@ enum ruby_special_exceptions {
     ruby_error_reenter,
     ruby_error_nomemory,
     ruby_error_sysstack,
-    ruby_error_closed_stream,
+    ruby_error_stream_closed,
     ruby_special_error_count
 };
 
@@ -490,6 +490,7 @@ typedef struct rb_vm_struct {
     struct rb_thread_struct *main_thread;
     struct rb_thread_struct *running_thread;
 
+    struct list_head waiting_fds; /* <=> struct waiting_fd */
     struct list_head living_threads;
     size_t living_thread_num;
     VALUE thgroup_default;
@@ -712,8 +713,6 @@ typedef struct rb_thread_struct {
     /* passing state */
     int state;
 
-    int waiting_fd;
-
     /* for rb_iterate */
     VALUE passed_block_handler;
 
@@ -1445,6 +1444,7 @@ void rb_thread_wakeup_timer_thread(void);
 static inline void
 rb_vm_living_threads_init(rb_vm_t *vm)
 {
+    list_head_init(&vm->waiting_fds);
     list_head_init(&vm->living_threads);
     vm->living_thread_num = 0;
 }