Updated epoll implementation.

ext/event/backend/epoll.c

@@ -27,6 +27,8 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
+#include "pidfd.c"
+
 static VALUE Event_Backend_EPoll = Qnil;
 static ID id_fileno;
 
@@ -113,6 +115,60 @@ VALUE Event_Backend_EPoll_close(VALUE self) {
 	return Qnil;
 }
 
+struct process_wait_arguments {
+	struct Event_Backend_EPoll *data;
+	pid_t pid;
+	int flags;
+	int descriptor;
+};
+
+static
+VALUE process_wait_transfer(VALUE _arguments) {
+	struct process_wait_arguments *arguments = (struct process_wait_arguments *)_arguments;
+
+	Event_Backend_transfer(arguments->data->loop);
+
+	return Event_Backend_process_status_wait(arguments->pid);
+}
+
+static
+VALUE process_wait_ensure(VALUE _arguments) {
+	struct process_wait_arguments *arguments = (struct process_wait_arguments *)_arguments;
+
+	// epoll_ctl(arguments->data->descriptor, EPOLL_CTL_DEL, arguments->descriptor, NULL);
+
+	close(arguments->descriptor);
+
+	return Qnil;
+}
+
+VALUE Event_Backend_EPoll_process_wait(VALUE self, VALUE fiber, VALUE pid, VALUE flags) {
+	struct Event_Backend_EPoll *data = NULL;
+	TypedData_Get_Struct(self, struct Event_Backend_EPoll, &Event_Backend_EPoll_Type, data);
+
+	struct process_wait_arguments process_wait_arguments = {
+		.data = data,
+		.pid = NUM2PIDT(pid),
+		.flags = NUM2INT(flags),
+	};
+
+	process_wait_arguments.descriptor = pidfd_open(process_wait_arguments.pid, 0);
+	rb_update_max_fd(process_wait_arguments.descriptor);
+
+	struct epoll_event event = {
+		.events = EPOLLIN|EPOLLRDHUP|EPOLLONESHOT,
+		.data = {.ptr = (void*)fiber},
+	};
+
+	int result = epoll_ctl(data->descriptor, EPOLL_CTL_ADD, process_wait_arguments.descriptor, &event);
+
+	if (result == -1) {
+		rb_sys_fail("epoll_ctl(process_wait)");
+	}
+
+	return rb_ensure(process_wait_transfer, (VALUE)&process_wait_arguments, process_wait_ensure, (VALUE)&process_wait_arguments);
+}
+
 static inline
 uint32_t epoll_flags_from_events(int events) {
 	uint32_t flags = 0;
@@ -296,61 +352,6 @@ VALUE Event_Backend_EPoll_select(VALUE self, VALUE duration) {
 	return INT2NUM(arguments.count);
 }
 
-VALUE Event_Backend_EPoll_process_wait(VALUE self, VALUE fiber, VALUE pid, VALUE flags) {
-	pid_t pidv = NUM2PIDT(pid);
-	int options = NUM2INT(flags);
-	int state = 0;
-	int err = 0;
-
-	if ((flags & WNOHANG) > 0) {
-		// WNOHANG is nonblock by default.
-		pid_t ret = PIDT2NUM(waitpid(pidv, &state, options));
-		if (ret == -1) err = errno;
-		return Event_Backend_process_status(pidv, state, err);
-	}
-
-	struct Event_Backend_EPoll *data = NULL;
-	TypedData_Get_Struct(self, struct Event_Backend_EPoll, &Event_Backend_EPoll_Type, data);
-
-	struct epoll_event event = {0};
-
-	int descriptor = pidfd_open(pidv, 0);
-	int duplicate = -1;
-
-	event.events = EPOLLIN | EPOLLRDHUP | EPOLLONESHOT;
-	event.data.ptr = (void*)fiber;
-
-	// A better approach is to batch all changes:
-	int result = epoll_ctl(data->descriptor, EPOLL_CTL_ADD, descriptor, &event);
-
-	if (result == -1 && errno == EEXIST) {
-		// The file descriptor was already inserted into epoll.
-		duplicate = descriptor = dup(descriptor);
-
-		rb_update_max_fd(duplicate);
-
-		if (descriptor == -1)
-			rb_sys_fail("dup");
-
-		result = epoll_ctl(data->descriptor, EPOLL_CTL_ADD, descriptor, &event);
-	}
-
-	if (result == -1) {
-		rb_sys_fail("epoll_ctl");
-	}
-
-	struct io_wait_arguments io_wait_arguments = {
-		.data = data,
-		.descriptor = descriptor,
-		.duplicate = duplicate
-	};
-
-	rb_ensure(io_wait_transfer, (VALUE)&io_wait_arguments, io_wait_ensure, (VALUE)&io_wait_arguments);
-	pid_t ret = PIDT2NUM(waitpid(pidv, &state, options));
-	if (ret == -1) err = errno;
-	return Event_Backend_process_status(pidv, state, err);
-}
-
 void Init_Event_Backend_EPoll(VALUE Event_Backend) {
 	id_fileno = rb_intern("fileno");
 

ext/event/backend/pidfd.c

@@ -0,0 +1,36 @@
+// Copyright, 2021, by Samuel G. D. Williams. <http://www.codeotaku.com>
+// 
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+// 
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+// 
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#include <sys/types.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+#include <poll.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#ifndef __NR_pidfd_open
+#define __NR_pidfd_open 434   /* System call # on most architectures */
+#endif
+
+static int
+pidfd_open(pid_t pid, unsigned int flags)
+{
+	return syscall(__NR_pidfd_open, pid, flags);
+}