From 134c363c7758ca6fcd3ca2215e3333e66bb2f98b Mon Sep 17 00:00:00 2001 Message-Id: <134c363c7758ca6fcd3ca2215e3333e66bb2f98b.1357726992.git.minovotn@redhat.com> In-Reply-To: <4f8efce613a639a3c1e3022c521d6c70b7154de8.1357726992.git.minovotn@redhat.com> References: <4f8efce613a639a3c1e3022c521d6c70b7154de8.1357726992.git.minovotn@redhat.com> From: Stefan Hajnoczi Date: Wed, 2 Jan 2013 15:02:30 +0100 Subject: [PATCH 07/16] dataplane: add event loop RH-Author: Stefan Hajnoczi Message-id: <1357138959-1918-8-git-send-email-stefanha@redhat.com> Patchwork-id: 45520 O-Subject: [RHEL6.4 qemu-kvm PATCH v5 07/16] dataplane: add event loop Bugzilla: 877836 RH-Acked-by: Laszlo Ersek RH-Acked-by: Michael S. Tsirkin RH-Acked-by: Paolo Bonzini 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 --- Makefile.target | 1 + hw/dataplane/event-poll.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++ hw/dataplane/event-poll.h | 40 +++++++++++++++++++ 3 files changed, 141 insertions(+) create mode 100644 hw/dataplane/event-poll.c create mode 100644 hw/dataplane/event-poll.h Signed-off-by: Michal Novotny --- Makefile.target | 1 + hw/dataplane/event-poll.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++ hw/dataplane/event-poll.h | 40 +++++++++++++++++++ 3 files changed, 141 insertions(+) create mode 100644 hw/dataplane/event-poll.c create mode 100644 hw/dataplane/event-poll.h diff --git a/Makefile.target b/Makefile.target index e573741..b9802e1 100644 --- a/Makefile.target +++ b/Makefile.target @@ -210,6 +210,7 @@ obj-y += vhost_net.o obj-$(CONFIG_VHOST_NET) += vhost.o obj-$(CONFIG_KVM) += kvm.o kvm-all.o hyperv.o obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += dataplane/hostmem.o dataplane/vring.o +obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += dataplane/event-poll.o # MSI-X depends on kvm for interrupt injection, # so moved it from Makefile.hw to Makefile.target for now obj-y += msix.o 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 + * + * 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 +#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..74c2b77 --- /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 + * + * 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 "hw/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 */ -- 1.7.11.7