Add wepoll support to light up the epoll backend on Windows

libevent is lacking a scalable backend on Windows. Let's leverage the wepoll
library until Windows comes up with an epoll/kqueue compete user mode API.

- All regress tests pass for standard wepoll
- These 2 tests fail intermittently for changelist wepoll, so disabling
  changelist wepoll for now
     http/cancel_inactive_server
     http/stream_in
- verify target on Windows runs tests for both wepoll and win32 backends
- wepoll backend preferred over win32 backend
- wepoll version 1.5.6

v2: cleaner backend abstraction. Disallow wepoll on MinGW/Cygwin.
v3: Add wepoll.h to dist
v4: Make sure wepoll source files are excluded from cygwin/mingw builds
v5: Keep win32 as default backend on windows.
v6: Include wepoll in mingw builds. Verified that regress tests pass w/ WEPOLL backend.
v7: Enable wepoll on mingw when building with cmake
v8: Add wepoll testrunner for autotools test target

CMakeLists.txt

@@ -514,6 +514,9 @@ set(EVENT_INCLUDES ${EVENT_INCLUDES} stdio.h)
 CHECK_SYMBOLS_EXIST("${SYMBOLS_TO_CHECK}" "${EVENT_INCLUDES}" "EVENT")
 unset(SYMBOLS_TO_CHECK)
 set(EVENT__HAVE_EPOLL ${EVENT__HAVE_EPOLL_CREATE})
+if(WIN32 AND NOT CYGWIN)
+    set(EVENT__HAVE_WEPOLL 1)
+endif()
 
 # Get the gethostbyname_r prototype.
 if(EVENT__HAVE_GETHOSTBYNAME_R)
@@ -839,6 +842,12 @@ if(EVENT__HAVE_EPOLL)
     list(APPEND SRC_CORE epoll.c)
 endif()
 
+if(EVENT__HAVE_WEPOLL)
+    list(APPEND SRC_CORE
+        epoll.c
+        wepoll.c)
+endif()
+
 if(EVENT__HAVE_EVENT_PORTS)
     list(APPEND SRC_CORE evport.c)
 endif()
@@ -1240,6 +1249,10 @@ if (NOT EVENT__DISABLE_TESTS)
         list(APPEND BACKENDS DEVPOLL)
     endif()
 
+    if (EVENT__HAVE_WEPOLL)
+        list(APPEND BACKENDS WEPOLL)
+    endif()
+
     if (WIN32)
         list(APPEND BACKENDS WIN32)
     endif()
@@ -1382,13 +1395,12 @@ if (NOT EVENT__DISABLE_TESTS)
     #  If they are set in the shell the tests are running using simply "ctest" or "make test" will fail)
     if (WIN32)
         # Windows doesn't have "unset". But you can use "set VAR=" instead.
-        # We need to guard against the possibility taht EVENT_NOWIN32 is set, and all test failing
-        # since no event backend being available.
         file(TO_NATIVE_PATH ${CMAKE_CTEST_COMMAND} WINDOWS_CTEST_COMMAND)
 
         file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/tmp/verify_tests.bat
             "
             set EVENT_NOWIN32=
+            set EVENT_NOWEPOLL=
             \"${WINDOWS_CTEST_COMMAND}\"
             ")
 
@@ -1410,7 +1422,7 @@ if (NOT EVENT__DISABLE_TESTS)
         add_custom_target(verify COMMAND "${VERIFY_PATH}"
                           DEPENDS event ${ALL_TESTPROGS})
     else()
-        # On some platforms doing exec(unset) as CMake does won't work, so make sure
+        # On some platforms doing exec(unset) as CMake doesn't work, so make sure
         # we run the unset command in a shell instead.
         # First we write the script contents.
         file(WRITE ${CMAKE_CURRENT_BINARY_DIR}/tmp/verify_tests.sh

LICENSE

@@ -97,3 +97,34 @@ 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.
+
+==============================
+
+The wepoll module is available under the following, sometimes called the
+"FreeBSD" license:
+
+Copyright 2012-2020, Bert Belder <[email protected]>
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+  * Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+
+  * Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in the
+    documentation and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Makefile.am

@@ -220,6 +220,10 @@ endif
 if EVPORT_BACKEND
 SYS_SRC += evport.c
 endif
+if WEPOLL_BACKEND
+SYS_SRC += epoll.c
+SYS_SRC += wepoll.c
+endif
 if SIGNAL_SUPPORT
 SYS_SRC += signal.c
 endif
@@ -323,7 +327,8 @@ noinst_HEADERS +=				\
 	strlcpy-internal.h			\
 	time-internal.h				\
 	util-internal.h				\
-	openssl-compat.h
+	openssl-compat.h			\
+	wepoll.h
 
 EVENT1_HDRS = \
 	include/evdns.h \

configure.ac

@@ -660,10 +660,16 @@ if test "x$haveeventports" = "xyes" ; then
 fi
 AM_CONDITIONAL(EVPORT_BACKEND, [test "x$haveeventports" = "xyes"])
 
+havewepoll=no
 if test "x$bwin32" = "xtrue"; then
 	needsignal=yes
+  if test "x$cygwin" = "xfalse"; then
+    havewepoll=yes
+    AC_DEFINE(HAVE_WEPOLL, 1,
+      [Define if your system supports the wepoll module])
+  fi
 fi
-
+AM_CONDITIONAL(WEPOLL_BACKEND, [test "x$havewepoll" = "xyes"])
 AM_CONDITIONAL(SIGNAL_SUPPORT, [test "x$needsignal" = "xyes"])
 
 AC_TYPE_PID_T

epoll.c

@@ -27,9 +27,18 @@
 #include "event2/event-config.h"
 #include "evconfig-private.h"
 
-#ifdef EVENT__HAVE_EPOLL
+#if defined EVENT__HAVE_EPOLL || defined EVENT__HAVE_WEPOLL
 
 #include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <limits.h>
+#include <string.h>
+
+#ifdef EVENT__HAVE_WEPOLL
+#include "wepoll.h"
+#define EPOLLET 0
+#else
 #include <sys/types.h>
 #include <sys/resource.h>
 #ifdef EVENT__HAVE_SYS_TIME_H
@@ -38,10 +47,6 @@
 #include <sys/queue.h>
 #include <sys/epoll.h>
 #include <signal.h>
-#include <limits.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
 #include <unistd.h>
 #include <errno.h>
 #ifdef EVENT__HAVE_FCNTL_H
@@ -50,6 +55,7 @@
 #ifdef EVENT__HAVE_SYS_TIMERFD_H
 #include <sys/timerfd.h>
 #endif
+#endif
 
 #include "event-internal.h"
 #include "evsignal-internal.h"
@@ -83,10 +89,20 @@
 #define USING_TIMERFD
 #endif
 
+#ifdef EVENT__HAVE_WEPOLL
+typedef HANDLE epoll_handle;
+#define INVALID_EPOLL_HANDLE NULL
+static void close_epoll_handle(HANDLE h) { epoll_close(h); }
+#else
+typedef int epoll_handle;
+#define INVALID_EPOLL_HANDLE -1
+static void close_epoll_handle(int h) { close(h); }
+#endif
+
 struct epollop {
 	struct epoll_event *events;
 	int nevents;
-	int epfd;
+	epoll_handle epfd;
 #ifdef USING_TIMERFD
 	int timerfd;
 #endif
@@ -114,6 +130,19 @@ static int epoll_nochangelist_add(struct event_base *base, evutil_socket_t fd,
 static int epoll_nochangelist_del(struct event_base *base, evutil_socket_t fd,
     short old, short events, void *p);
 
+#ifdef EVENT__HAVE_WEPOLL
+const struct eventop wepollops = {
+	"wepoll",
+	epoll_init,
+	epoll_nochangelist_add,
+	epoll_nochangelist_del,
+	epoll_dispatch,
+	epoll_dealloc,
+	1, /* need reinit */
+	EV_FEATURE_O1|EV_FEATURE_EARLY_CLOSE,
+	0
+};
+#else
 const struct eventop epollops = {
 	"epoll",
 	epoll_init,
@@ -125,6 +154,8 @@ const struct eventop epollops = {
 	EV_FEATURE_ET|EV_FEATURE_O1|EV_FEATURE_EARLY_CLOSE,
 	0
 };
+#endif
+
 
 #define INITIAL_NEVENT 32
 #define MAX_NEVENT 4096
@@ -140,26 +171,28 @@ const struct eventop epollops = {
 static void *
 epoll_init(struct event_base *base)
 {
-	int epfd = -1;
+	epoll_handle epfd = INVALID_EPOLL_HANDLE;
 	struct epollop *epollop;
 
 #ifdef EVENT__HAVE_EPOLL_CREATE1
 	/* First, try the shiny new epoll_create1 interface, if we have it. */
 	epfd = epoll_create1(EPOLL_CLOEXEC);
 #endif
-	if (epfd == -1) {
+	if (epfd == INVALID_EPOLL_HANDLE) {
 		/* Initialize the kernel queue using the old interface.  (The
 		size field is ignored   since 2.6.8.) */
-		if ((epfd = epoll_create(32000)) == -1) {
+		if ((epfd = epoll_create(32000)) == INVALID_EPOLL_HANDLE) {
 			if (errno != ENOSYS)
 				event_warn("epoll_create");
 			return (NULL);
 		}
+#ifndef EVENT__HAVE_WEPOLL
 		evutil_make_socket_closeonexec(epfd);
+#endif
 	}
 
 	if (!(epollop = mm_calloc(1, sizeof(struct epollop)))) {
-		close(epfd);
+		close_epoll_handle(epfd);
 		return (NULL);
 	}
 
@@ -169,17 +202,19 @@ epoll_init(struct event_base *base)
 	epollop->events = mm_calloc(INITIAL_NEVENT, sizeof(struct epoll_event));
 	if (epollop->events == NULL) {
 		mm_free(epollop);
-		close(epfd);
+		close_epoll_handle(epfd);
 		return (NULL);
 	}
 	epollop->nevents = INITIAL_NEVENT;
 
+#ifndef EVENT__HAVE_WEPOLL
 	if ((base->flags & EVENT_BASE_FLAG_EPOLL_USE_CHANGELIST) != 0 ||
 	    ((base->flags & EVENT_BASE_FLAG_IGNORE_ENV) == 0 &&
 		evutil_getenv_("EVENT_EPOLL_USE_CHANGELIST") != NULL)) {
 
 		base->evsel = &epollops_changelist;
 	}
+#endif
 
 #ifdef USING_TIMERFD
 	/*
@@ -286,7 +321,11 @@ epoll_apply_one_change(struct event_base *base,
 		events |= EPOLLET;
 
 	memset(&epev, 0, sizeof(epev));
+#ifdef EVENT__HAVE_WEPOLL
+	epev.data.sock = ch->fd;
+#else
 	epev.data.fd = ch->fd;
+#endif
 	epev.events = events;
 	if (epoll_ctl(epollop->epfd, op, ch->fd, &epev) == 0) {
 		event_debug((PRINT_CHANGES(op, epev.events, ch, "okay")));
@@ -503,7 +542,11 @@ epoll_dispatch(struct event_base *base, struct timeval *tv)
 		if (!ev)
 			continue;
 
+#ifdef EVENT__HAVE_WEPOLL
+		evmap_io_active_(base, events[i].data.sock, ev);
+#else
 		evmap_io_active_(base, events[i].data.fd, ev | EV_ET);
+#endif
 	}
 
 	if (res == epollop->nevents && epollop->nevents < MAX_NEVENT) {
@@ -532,8 +575,8 @@ epoll_dealloc(struct event_base *base)
 	evsig_dealloc_(base);
 	if (epollop->events)
 		mm_free(epollop->events);
-	if (epollop->epfd >= 0)
-		close(epollop->epfd);
+	if (epollop->epfd != INVALID_EPOLL_HANDLE)
+		close_epoll_handle(epollop->epfd);
 #ifdef USING_TIMERFD
 	if (epollop->timerfd >= 0)
 		close(epollop->timerfd);
@@ -543,4 +586,4 @@ epoll_dealloc(struct event_base *base)
 	mm_free(epollop);
 }
 
-#endif /* EVENT__HAVE_EPOLL */
+#endif /* defined EVENT__HAVE_EPOLL || defined EVENT__HAVE_WEPOLL */

event-config.h.cmake

@@ -102,6 +102,9 @@
 /* Define to 1 if you have the `epoll_ctl' function. */
 #cmakedefine EVENT__HAVE_EPOLL_CTL 1
 
+/* Define if your system supports the wepoll module */
+#cmakedefine EVENT__HAVE_WEPOLL 1
+
 /* Define to 1 if you have the `eventfd' function. */
 #cmakedefine EVENT__HAVE_EVENTFD 1
 

event.c

@@ -96,6 +96,9 @@ extern const struct eventop kqops;
 #ifdef EVENT__HAVE_DEVPOLL
 extern const struct eventop devpollops;
 #endif
+#ifdef EVENT__HAVE_WEPOLL
+extern const struct eventop wepollops;
+#endif
 #ifdef _WIN32
 extern const struct eventop win32ops;
 #endif
@@ -122,6 +125,9 @@ static const struct eventop *eventops[] = {
 #endif
 #ifdef _WIN32
 	&win32ops,
+#endif
+#ifdef EVENT__HAVE_WEPOLL
+	&wepollops,
 #endif
 	NULL
 };

test/include.am

@@ -51,6 +51,7 @@ TESTS = \
 	test_runner_devpoll \
 	test_runner_poll \
 	test_runner_win32 \
+	test_runner_wepoll \
 	test_runner_timerfd \
 	test_runner_changelist \
 	test_runner_timerfd_changelist
@@ -71,6 +72,8 @@ test_runner_poll: $(top_srcdir)/test/test.sh
 	$(top_srcdir)/test/test.sh -b POLL
 test_runner_win32: $(top_srcdir)/test/test.sh
 	$(top_srcdir)/test/test.sh -b WIN32
+test_runner_wepoll: $(top_srcdir)/test/test.sh
+	$(top_srcdir)/test/test.sh -b WEPOLL
 test_runner_timerfd: $(top_srcdir)/test/test.sh
 	$(top_srcdir)/test/test.sh -b "" -t
 test_runner_changelist: $(top_srcdir)/test/test.sh

test/test.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 
-BACKENDS="EVPORT KQUEUE EPOLL DEVPOLL POLL SELECT WIN32"
+BACKENDS="EVPORT KQUEUE EPOLL DEVPOLL POLL SELECT WIN32 WEPOLL"
 TESTS="test-eof test-closed test-weof test-time test-changelist test-fdleak"
 FAILED=no
 TEST_OUTPUT_FILE=${TEST_OUTPUT_FILE:-/dev/null}