Make waiting_fd behaviour per-IO. (ruby#13127)

- `rb_thread_fd_close` is deprecated and now a no-op.
- IO operations (including close) no longer take a vm-wide lock.

Author: ioquatix

NEWS.md

@@ -102,6 +102,19 @@ The following bundled gems are updated.
 
 ## C API updates
 
+* IO
+
+    * `rb_thread_fd_close` is deprecated and now a no-op. If you need to expose
+      file descriptors from C extensions to Ruby code, create an `IO` instance
+      using `RUBY_IO_MODE_EXTERNAL` and use `rb_io_close(io)` to close it (this
+      also interrupts and waits for all pending operations on the `IO`
+      instance). Directly closing file descriptors does not interrupt pending
+      operations, and may lead to undefined beahviour. In other words, if two
+      `IO` objects share the same file descriptor, closing one does not affect
+      the other. [[Feature #18455]]
+
+ [[Feature #18455]]
+
 ## Implementation improvements
 
 ## JIT
@@ -112,3 +125,4 @@ The following bundled gems are updated.
 [Bug #21049]:     https://bugs.ruby-lang.org/issues/21049
 [Feature #21216]: https://bugs.ruby-lang.org/issues/21216
 [Feature #21258]: https://bugs.ruby-lang.org/issues/21258
+[Feature #18455]: https://bugs.ruby-lang.org/issues/18455

ext/-test-/thread_fd/depend

@@ -3204,6 +3204,7 @@ rb_gc_mark_children(void *objspace, VALUE obj)
             gc_mark_internal(RFILE(obj)->fptr->encs.ecopts);
             gc_mark_internal(RFILE(obj)->fptr->write_lock);
             gc_mark_internal(RFILE(obj)->fptr->timeout);
+            gc_mark_internal(RFILE(obj)->fptr->wakeup_mutex);
         }
         break;
 
@@ -4185,6 +4186,8 @@ rb_gc_update_object_references(void *objspace, VALUE obj)
             UPDATE_IF_MOVED(objspace, RFILE(obj)->fptr->writeconv_pre_ecopts);
             UPDATE_IF_MOVED(objspace, RFILE(obj)->fptr->encs.ecopts);
             UPDATE_IF_MOVED(objspace, RFILE(obj)->fptr->write_lock);
+            UPDATE_IF_MOVED(objspace, RFILE(obj)->fptr->timeout);
+            UPDATE_IF_MOVED(objspace, RFILE(obj)->fptr->wakeup_mutex);
         }
         break;
       case T_REGEXP:

ext/-test-/thread_fd/extconf.rb

@@ -61,10 +61,10 @@ int rb_thread_wait_fd(int fd);
 int rb_thread_fd_writable(int fd);
 
 /**
- * Notifies a closing of a file  descriptor to other threads.  Multiple threads
- * can wait for the given file descriptor  at once.  If such file descriptor is
- * closed, threads need to start propagating their exceptions.  This is the API
- * to kick that process.
+ * This funciton is now a no-op. It was previously used to interrupt threads
+ * that were using the given file descriptor and wait for them to finish.
+ *
+ * @deprecated Use IO with RUBY_IO_MODE_EXTERNAL and `rb_io_close` instead.
  *
  * @param[in]  fd  A file descriptor.
  * @note       This function blocks  until all the threads waiting  for such fd

ext/-test-/thread_fd/thread_fd.c

@@ -14,10 +14,20 @@
 struct rb_io;
 
 #include "ruby/io.h"            /* for rb_io_t */
+#include "ccan/list/list.h"
 
 #define IO_WITHOUT_GVL(func, arg) rb_nogvl(func, arg, RUBY_UBF_IO, 0, RB_NOGVL_OFFLOAD_SAFE)
 #define IO_WITHOUT_GVL_INT(func, arg) (int)(VALUE)IO_WITHOUT_GVL(func, arg)
 
+// Represents an in-flight blocking operation:
+struct rb_io_blocking_operation {
+    // The linked list data structure.
+    struct ccan_list_node list;
+
+    // The execution context of the blocking operation:
+    struct rb_execution_context_struct *ec;
+};
+
 /** Ruby's IO, metadata and buffers. */
 struct rb_io {
 
@@ -111,6 +121,15 @@ struct rb_io {
      * The timeout associated with this IO when performing blocking operations.
      */
     VALUE timeout;
+
+    /**
+     * Threads that are performing a blocking operation without the GVL using
+     * this IO. On calling IO#close, these threads will be interrupted so that
+     * the operation can be cancelled.
+     */
+    struct ccan_list_head blocking_operations;
+    struct rb_execution_context_struct *closing_ec;
+    VALUE wakeup_mutex;
 };
 
 /* io.c */
@@ -125,7 +144,7 @@ VALUE rb_io_prep_stdin(void);
 VALUE rb_io_prep_stdout(void);
 VALUE rb_io_prep_stderr(void);
 
-int rb_io_fptr_finalize(struct rb_io *fptr);
+int rb_io_notify_close(struct rb_io *fptr);
 
 RUBY_SYMBOL_EXPORT_BEGIN
 /* io.c (export) */

gc.c

@@ -13,6 +13,7 @@
 #include "ccan/list/list.h"     /* for list in rb_io_close_wait_list */
 
 struct rb_thread_struct;        /* in vm_core.h */
+struct rb_io;
 
 #define RB_VM_SAVE_MACHINE_CONTEXT(th)				\
     do {							\
@@ -58,14 +59,8 @@ void ruby_mn_threads_params(void);
 int rb_thread_io_wait(struct rb_io *io, int events, struct timeval * timeout);
 int rb_thread_wait_for_single_fd(int fd, int events, struct timeval * timeout);
 
-struct rb_io_close_wait_list {
-    struct ccan_list_head pending_fd_users;
-    VALUE closing_thread;
-    VALUE closing_fiber;
-    VALUE wakeup_mutex;
-};
-int rb_notify_fd_close(int fd, struct rb_io_close_wait_list *busy);
-void rb_notify_fd_close_wait(struct rb_io_close_wait_list *busy);
+size_t rb_thread_io_close_interrupt(struct rb_io *);
+void rb_thread_io_close_wait(struct rb_io *);
 
 void rb_ec_check_ints(struct rb_execution_context_struct *ec);