r20539: - split the common timer related events code into events_timed.c

- make it easier to plug in a new events backend

- add simpler 'select' and 'epoll' backends

This is part of the effort to add good AIO support. The events_aio.c
backend is done, but sometimes dies with a SEGV, which is why it isn't
enabled yet.
(This used to be commit 934f18283dbc7958944931a93a854526bcd54884)

1 files changed, 407 insertions, 0 deletions

diff --git a/source4/lib/events/events_epoll.c b/source4/lib/events/events_epoll.c
new file mode 100644
index 00000000000..cd894d8dff1
--- /dev/null
+++ b/source4/lib/events/events_epoll.c
@@ -0,0 +1,407 @@
+/* 
+   Unix SMB/CIFS implementation.
+
+   main select loop and event handling - epoll implementation
+
+   Copyright (C) Andrew Tridgell	2003-2005
+   Copyright (C) Stefan Metzmacher	2005
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "includes.h"
+#include "system/filesys.h"
+#include "system/select.h" /* needed for WITH_EPOLL */
+#include "lib/util/dlinklist.h"
+#include "lib/events/events.h"
+#include "lib/events/events_internal.h"
+
+struct epoll_event_context {
+	/* a pointer back to the generic event_context */
+	struct event_context *ev;
+
+	/* number of registered fd event handlers */
+	int num_fd_events;
+
+	/* this is changed by the destructors for the fd event
+	   type. It is used to detect event destruction by event
+	   handlers, which means the code that is calling the event
+	   handler needs to assume that the linked list is no longer
+	   valid
+	*/
+	uint32_t destruction_count;
+
+	/* when using epoll this is the handle from epoll_create */
+	int epoll_fd;
+};
+
+/*
+  called when a epoll call fails, and we should fallback
+  to using select
+*/
+static void epoll_fallback_to_select(struct epoll_event_context *epoll_ev, const char *reason)
+{
+	DEBUG(0,("%s (%s) - falling back to select()\n", reason, strerror(errno)));
+	close(epoll_ev->epoll_fd);
+	epoll_ev->epoll_fd = -1;
+	talloc_set_destructor(epoll_ev, NULL);
+}
+
+/*
+  map from EVENT_FD_* to EPOLLIN/EPOLLOUT
+*/
+static uint32_t epoll_map_flags(uint16_t flags)
+{
+	uint32_t ret = 0;
+	if (flags & EVENT_FD_READ) ret |= (EPOLLIN | EPOLLERR | EPOLLHUP);
+	if (flags & EVENT_FD_WRITE) ret |= (EPOLLOUT | EPOLLERR | EPOLLHUP);
+	return ret;
+}
+
+/*
+ free the epoll fd
+*/
+static int epoll_ctx_destructor(struct epoll_event_context *epoll_ev)
+{
+	close(epoll_ev->epoll_fd);
+	epoll_ev->epoll_fd = -1;
+	return 0;
+}
+
+/*
+ init the epoll fd
+*/
+static void epoll_init_ctx(struct epoll_event_context *epoll_ev)
+{
+	epoll_ev->epoll_fd = epoll_create(64);
+	talloc_set_destructor(epoll_ev, epoll_ctx_destructor);
+}
+
+#define EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT	(1<<0)
+#define EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR	(1<<1)
+#define EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR	(1<<2)
+
+/*
+ add the epoll event to the given fd_event
+*/
+static void epoll_add_event(struct epoll_event_context *epoll_ev, struct fd_event *fde)
+{
+	struct epoll_event event;
+	if (epoll_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	/* if we don't want events yet, don't add an epoll_event */
+	if (fde->flags == 0) return;
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	event.data.ptr = fde;
+	if (epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_ADD, fde->fd, &event) != 0) {
+		epoll_fallback_to_select(epoll_ev, "EPOLL_CTL_ADD failed");
+	}
+	fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+
+	/* only if we want to read we want to tell the event handler about errors */
+	if (fde->flags & EVENT_FD_READ) {
+		fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+}
+
+/*
+ delete the epoll event for given fd_event
+*/
+static void epoll_del_event(struct epoll_event_context *epoll_ev, struct fd_event *fde)
+{
+	struct epoll_event event;
+	if (epoll_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	/* if there's no epoll_event, we don't need to delete it */
+	if (!(fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT)) return;
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	event.data.ptr = fde;
+	epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_DEL, fde->fd, &event);
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
+}
+
+/*
+ change the epoll event to the given fd_event
+*/
+static void epoll_mod_event(struct epoll_event_context *epoll_ev, struct fd_event *fde)
+{
+	struct epoll_event event;
+	if (epoll_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	ZERO_STRUCT(event);
+	event.events = epoll_map_flags(fde->flags);
+	event.data.ptr = fde;
+	if (epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_MOD, fde->fd, &event) != 0) {
+		epoll_fallback_to_select(epoll_ev, "EPOLL_CTL_MOD failed");
+	}
+
+	/* only if we want to read we want to tell the event handler about errors */
+	if (fde->flags & EVENT_FD_READ) {
+		fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+	}
+}
+
+static void epoll_change_event(struct epoll_event_context *epoll_ev, struct fd_event *fde)
+{
+	BOOL got_error = (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR);
+	BOOL want_read = (fde->flags & EVENT_FD_READ);
+	BOOL want_write= (fde->flags & EVENT_FD_WRITE);
+
+	if (epoll_ev->epoll_fd == -1) return;
+
+	fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
+
+	/* there's already an event */
+	if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT) {
+		if (want_read || (want_write && !got_error)) {
+			epoll_mod_event(epoll_ev, fde);
+			return;
+		}
+		/* 
+		 * if we want to match the select behavior, we need to remove the epoll_event
+		 * when the caller isn't interested in events.
+		 *
+		 * this is because epoll reports EPOLLERR and EPOLLHUP, even without asking for them
+		 */
+		epoll_del_event(epoll_ev, fde);
+		return;
+	}
+
+	/* there's no epoll_event attached to the fde */
+	if (want_read || (want_write && !got_error)) {
+		epoll_add_event(epoll_ev, fde);
+		return;
+	}
+}
+
+/*
+  event loop handling using epoll
+*/
+static int epoll_event_loop(struct epoll_event_context *epoll_ev, struct timeval *tvalp)
+{
+	int ret, i;
+#define MAXEVENTS 8
+	struct epoll_event events[MAXEVENTS];
+	uint32_t destruction_count = epoll_ev->destruction_count;
+	int timeout = -1;
+
+	if (epoll_ev->epoll_fd == -1) return -1;
+
+	if (tvalp) {
+		/* it's better to trigger timed events a bit later than to early */
+		timeout = ((tvalp->tv_usec+999) / 1000) + (tvalp->tv_sec*1000);
+	}
+
+	ret = epoll_wait(epoll_ev->epoll_fd, events, MAXEVENTS, timeout);
+
+	if (ret == -1 && errno != EINTR) {
+		epoll_fallback_to_select(epoll_ev, "epoll_wait() failed");
+		return -1;
+	}
+
+	if (ret == 0 && tvalp) {
+		common_event_loop_timer(epoll_ev->ev);
+		return 0;
+	}
+
+	for (i=0;i<ret;i++) {
+		struct fd_event *fde = talloc_get_type(events[i].data.ptr, 
+						       struct fd_event);
+		uint16_t flags = 0;
+
+		if (fde == NULL) {
+			epoll_fallback_to_select(epoll_ev, "epoll_wait() gave bad data");
+			return -1;
+		}
+		if (events[i].events & (EPOLLHUP|EPOLLERR)) {
+			fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
+			/*
+			 * if we only wait for EVENT_FD_WRITE, we should not tell the
+			 * event handler about it, and remove the epoll_event,
+			 * as we only report errors when waiting for read events,
+			 * to match the select() behavior
+			 */
+			if (!(fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR)) {
+				epoll_del_event(epoll_ev, fde);
+				continue;
+			}
+			flags |= EVENT_FD_READ;
+		}
+		if (events[i].events & EPOLLIN) flags |= EVENT_FD_READ;
+		if (events[i].events & EPOLLOUT) flags |= EVENT_FD_WRITE;
+		if (flags) {
+			fde->handler(epoll_ev->ev, fde, flags, fde->private_data);
+			if (destruction_count != epoll_ev->destruction_count) {
+				break;
+			}
+		}
+	}
+
+	return 0;
+}
+
+/*
+  create a epoll_event_context structure.
+*/
+static int epoll_event_context_init(struct event_context *ev)
+{
+	struct epoll_event_context *epoll_ev;
+
+	epoll_ev = talloc_zero(ev, struct epoll_event_context);
+	if (!epoll_ev) return -1;
+	epoll_ev->ev = ev;
+	epoll_ev->epoll_fd = -1;
+
+	epoll_init_ctx(epoll_ev);
+
+	ev->additional_data = epoll_ev;
+	return 0;
+}
+
+/*
+  destroy an fd_event
+*/
+static int epoll_event_fd_destructor(struct fd_event *fde)
+{
+	struct event_context *ev = fde->event_ctx;
+	struct epoll_event_context *epoll_ev = talloc_get_type(ev->additional_data,
+							   struct epoll_event_context);
+
+	epoll_ev->num_fd_events--;
+	epoll_ev->destruction_count++;
+
+	epoll_del_event(epoll_ev, fde);
+
+	return 0;
+}
+
+/*
+  add a fd based event
+  return NULL on failure (memory allocation error)
+*/
+static struct fd_event *epoll_event_add_fd(struct event_context *ev, TALLOC_CTX *mem_ctx,
+					 int fd, uint16_t flags,
+					 event_fd_handler_t handler,
+					 void *private_data)
+{
+	struct epoll_event_context *epoll_ev = talloc_get_type(ev->additional_data,
+							   struct epoll_event_context);
+	struct fd_event *fde;
+
+	fde = talloc(mem_ctx?mem_ctx:ev, struct fd_event);
+	if (!fde) return NULL;
+
+	fde->event_ctx		= ev;
+	fde->fd			= fd;
+	fde->flags		= flags;
+	fde->handler		= handler;
+	fde->private_data	= private_data;
+	fde->additional_flags	= 0;
+	fde->additional_data	= NULL;
+
+	epoll_ev->num_fd_events++;
+	talloc_set_destructor(fde, epoll_event_fd_destructor);
+
+	epoll_add_event(epoll_ev, fde);
+
+	return fde;
+}
+
+
+/*
+  return the fd event flags
+*/
+static uint16_t epoll_event_get_fd_flags(struct fd_event *fde)
+{
+	return fde->flags;
+}
+
+/*
+  set the fd event flags
+*/
+static void epoll_event_set_fd_flags(struct fd_event *fde, uint16_t flags)
+{
+	struct event_context *ev;
+	struct epoll_event_context *epoll_ev;
+
+	if (fde->flags == flags) return;
+
+	ev = fde->event_ctx;
+	epoll_ev = talloc_get_type(ev->additional_data, struct epoll_event_context);
+
+	fde->flags = flags;
+
+	epoll_change_event(epoll_ev, fde);
+}
+
+/*
+  do a single event loop using the events defined in ev 
+*/
+static int epoll_event_loop_once(struct event_context *ev)
+{
+	struct epoll_event_context *epoll_ev = talloc_get_type(ev->additional_data,
+		 					   struct epoll_event_context);
+	struct timeval tval;
+
+	tval = common_event_loop_delay(ev);
+
+	if (timeval_is_zero(&tval)) {
+		common_event_loop_timer(ev);
+		return 0;
+	}
+
+	return epoll_event_loop(epoll_ev, &tval);
+}
+
+/*
+  return on failure or (with 0) if all fd events are removed
+*/
+static int epoll_event_loop_wait(struct event_context *ev)
+{
+	struct epoll_event_context *epoll_ev = talloc_get_type(ev->additional_data,
+							   struct epoll_event_context);
+	while (epoll_ev->num_fd_events) {
+		if (epoll_event_loop_once(ev) != 0) {
+			break;
+		}
+	}
+
+	return 0;
+}
+
+static const struct event_ops epoll_event_ops = {
+	.context_init	= epoll_event_context_init,
+	.add_fd		= epoll_event_add_fd,
+	.get_fd_flags	= epoll_event_get_fd_flags,
+	.set_fd_flags	= epoll_event_set_fd_flags,
+	.add_timed	= common_event_add_timed,
+	.loop_once	= epoll_event_loop_once,
+	.loop_wait	= epoll_event_loop_wait,
+};
+
+NTSTATUS events_epoll_init(void)
+{
+	return event_register_backend("epoll", &epoll_event_ops);
+}