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[Qemu-devel] [PATCH 05/18] dataplane: add event loop
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH 05/18] dataplane: add event loop |
Date: |
Wed, 19 Dec 2012 16:38:06 +0100 |
Outside the safety of the global mutex we need to poll on file
descriptors. I found epoll(2) is a convenient way to do that, although
other options could replace this module in the future (such as an
AioContext-based loop or glib's GMainLoop).
One important feature of this small event loop implementation is that
the loop can be terminated in a thread-safe way. This allows QEMU to
stop the data plane thread cleanly.
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
hw/dataplane/Makefile.objs | 2 +-
hw/dataplane/event-poll.c | 100 +++++++++++++++++++++++++++++++++++++++++++++
hw/dataplane/event-poll.h | 40 ++++++++++++++++++
3 files changed, 141 insertions(+), 1 deletion(-)
create mode 100644 hw/dataplane/event-poll.c
create mode 100644 hw/dataplane/event-poll.h
diff --git a/hw/dataplane/Makefile.objs b/hw/dataplane/Makefile.objs
index 34e6d57..e26bd7d 100644
--- a/hw/dataplane/Makefile.objs
+++ b/hw/dataplane/Makefile.objs
@@ -1,3 +1,3 @@
ifeq ($(CONFIG_VIRTIO), y)
-common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o
+common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += hostmem.o vring.o event-poll.o
endif
diff --git a/hw/dataplane/event-poll.c b/hw/dataplane/event-poll.c
new file mode 100644
index 0000000..2b55c6e
--- /dev/null
+++ b/hw/dataplane/event-poll.c
@@ -0,0 +1,100 @@
+/*
+ * Event loop with file descriptor polling
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include <sys/epoll.h>
+#include "hw/dataplane/event-poll.h"
+
+/* Add an event notifier and its callback for polling */
+void event_poll_add(EventPoll *poll, EventHandler *handler,
+ EventNotifier *notifier, EventCallback *callback)
+{
+ struct epoll_event event = {
+ .events = EPOLLIN,
+ .data.ptr = handler,
+ };
+ handler->notifier = notifier;
+ handler->callback = callback;
+ if (epoll_ctl(poll->epoll_fd, EPOLL_CTL_ADD,
+ event_notifier_get_fd(notifier), &event) != 0) {
+ fprintf(stderr, "failed to add event handler to epoll: %m\n");
+ exit(1);
+ }
+}
+
+/* Event callback for stopping event_poll() */
+static void handle_stop(EventHandler *handler)
+{
+ /* Do nothing */
+}
+
+void event_poll_init(EventPoll *poll)
+{
+ /* Create epoll file descriptor */
+ poll->epoll_fd = epoll_create1(EPOLL_CLOEXEC);
+ if (poll->epoll_fd < 0) {
+ fprintf(stderr, "epoll_create1 failed: %m\n");
+ exit(1);
+ }
+
+ /* Set up stop notifier */
+ if (event_notifier_init(&poll->stop_notifier, 0) < 0) {
+ fprintf(stderr, "failed to init stop notifier\n");
+ exit(1);
+ }
+ event_poll_add(poll, &poll->stop_handler,
+ &poll->stop_notifier, handle_stop);
+}
+
+void event_poll_cleanup(EventPoll *poll)
+{
+ event_notifier_cleanup(&poll->stop_notifier);
+ close(poll->epoll_fd);
+ poll->epoll_fd = -1;
+}
+
+/* Block until the next event and invoke its callback */
+void event_poll(EventPoll *poll)
+{
+ EventHandler *handler;
+ struct epoll_event event;
+ int nevents;
+
+ /* Wait for the next event. Only do one event per call to keep the
+ * function simple, this could be changed later. */
+ do {
+ nevents = epoll_wait(poll->epoll_fd, &event, 1, -1);
+ } while (nevents < 0 && errno == EINTR);
+ if (unlikely(nevents != 1)) {
+ fprintf(stderr, "epoll_wait failed: %m\n");
+ exit(1); /* should never happen */
+ }
+
+ /* Find out which event handler has become active */
+ handler = event.data.ptr;
+
+ /* Clear the eventfd */
+ event_notifier_test_and_clear(handler->notifier);
+
+ /* Handle the event */
+ handler->callback(handler);
+}
+
+/* Stop event_poll()
+ *
+ * This function can be used from another thread.
+ */
+void event_poll_notify(EventPoll *poll)
+{
+ event_notifier_set(&poll->stop_notifier);
+}
diff --git a/hw/dataplane/event-poll.h b/hw/dataplane/event-poll.h
new file mode 100644
index 0000000..ed3456c
--- /dev/null
+++ b/hw/dataplane/event-poll.h
@@ -0,0 +1,40 @@
+/*
+ * Event loop with file descriptor polling
+ *
+ * Copyright 2012 IBM, Corp.
+ * Copyright 2012 Red Hat, Inc. and/or its affiliates
+ *
+ * Authors:
+ * Stefan Hajnoczi <address@hidden>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef EVENT_POLL_H
+#define EVENT_POLL_H
+
+#include "event_notifier.h"
+
+typedef struct EventHandler EventHandler;
+typedef void EventCallback(EventHandler *handler);
+struct EventHandler {
+ EventNotifier *notifier; /* eventfd */
+ EventCallback *callback; /* callback function */
+};
+
+typedef struct {
+ int epoll_fd; /* epoll(2) file descriptor */
+ EventNotifier stop_notifier; /* stop poll notifier */
+ EventHandler stop_handler; /* stop poll handler */
+} EventPoll;
+
+void event_poll_add(EventPoll *poll, EventHandler *handler,
+ EventNotifier *notifier, EventCallback *callback);
+void event_poll_init(EventPoll *poll);
+void event_poll_cleanup(EventPoll *poll);
+void event_poll(EventPoll *poll);
+void event_poll_notify(EventPoll *poll);
+
+#endif /* EVENT_POLL_H */
--
1.8.0.2
- [Qemu-devel] [PULL 00/18] Block patches, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 01/18] raw-posix: add raw_get_aio_fd() for virtio-blk-data-plane, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 02/18] configure: add CONFIG_VIRTIO_BLK_DATA_PLANE, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 03/18] dataplane: add host memory mapping code, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 04/18] dataplane: add virtqueue vring code, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 06/18] dataplane: add Linux AIO request queue, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 05/18] dataplane: add event loop,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH 10/18] virtio-blk: restore VirtIOBlkConf->config_wce flag, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 09/18] iov: add qemu_iovec_concat_iov(), Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 12/18] virtio-blk: add x-data-plane=on|off performance feature, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 11/18] dataplane: add virtio-blk data plane code, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 13/18] virtio-blk: Return UNSUPP for unknown request types, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 14/18] cutils: change strtosz_suffix_unit function, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 16/18] block/raw-win32: Fix compiler warnings (wrong format specifiers), Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 15/18] qemu-img: report size overflow error message, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 08/18] test-iov: add iov_discard_front/back() testcases, Stefan Hajnoczi, 2012/12/19
- [Qemu-devel] [PATCH 07/18] iov: add iov_discard_front/back() to remove data, Stefan Hajnoczi, 2012/12/19