From patchwork Thu Nov 15 15:19:03 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Hajnoczi X-Patchwork-Id: 199336 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id E56982C033E for ; Fri, 16 Nov 2012 03:11:46 +1100 (EST) Received: from localhost ([::1]:56933 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TZ1EZ-0004ee-VE for incoming@patchwork.ozlabs.org; Thu, 15 Nov 2012 10:20:03 -0500 Received: from eggs.gnu.org ([208.118.235.92]:59562) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TZ1E0-0003AJ-NP for qemu-devel@nongnu.org; Thu, 15 Nov 2012 10:19:31 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TZ1Dx-0006nS-Kg for qemu-devel@nongnu.org; Thu, 15 Nov 2012 10:19:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:13154) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TZ1Dx-0006nA-CV for qemu-devel@nongnu.org; Thu, 15 Nov 2012 10:19:25 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id qAFFJOuD015106 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 15 Nov 2012 10:19:24 -0500 Received: from localhost (ovpn-112-20.ams2.redhat.com [10.36.112.20]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id qAFFJNIX021128; Thu, 15 Nov 2012 10:19:24 -0500 From: Stefan Hajnoczi To: Date: Thu, 15 Nov 2012 16:19:03 +0100 Message-Id: <1352992746-8767-5-git-send-email-stefanha@redhat.com> In-Reply-To: <1352992746-8767-1-git-send-email-stefanha@redhat.com> References: <1352992746-8767-1-git-send-email-stefanha@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Kevin Wolf , Anthony Liguori , "Michael S. Tsirkin" , khoa@us.ibm.com, Stefan Hajnoczi , Paolo Bonzini , Asias He Subject: [Qemu-devel] [PATCH 4/7] dataplane: add event loop X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org 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 --- hw/dataplane/Makefile.objs | 2 +- hw/dataplane/event-poll.c | 109 +++++++++++++++++++++++++++++++++++++++++++++ hw/dataplane/event-poll.h | 40 +++++++++++++++++ 3 files changed, 150 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 b58544f..a01ad05 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) += vring.o +common-obj-$(CONFIG_VIRTIO_BLK_DATA_PLANE) += 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..4a53d48 --- /dev/null +++ b/hw/dataplane/event-poll.c @@ -0,0 +1,109 @@ +/* + * 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 the event_poll_run() loop */ +static bool handle_stop(EventHandler *handler) +{ + return false; /* stop event loop */ +} + +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 + * + * Signals must be masked, EINTR should never happen. This is true for QEMU + * threads. + */ +static bool 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. */ + nevents = epoll_wait(poll->epoll_fd, &event, 1, -1); + 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 */ + return handler->callback(handler); +} + +void event_poll_run(EventPoll *poll) +{ + while (event_poll(poll)) { + /* do nothing */ + } +} + +/* Stop the event_poll_run() loop + * + * This function can be used from another thread. + */ +void event_poll_stop(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..5e1771f --- /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 "event_notifier.h" + +typedef struct EventHandler EventHandler; +typedef bool 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_run(EventPoll *poll); +void event_poll_stop(EventPoll *poll); + +#endif /* EVENT_POLL_H */