Re: [libvirt PATCH 05/11] src: introduce an abstraction for running event loops

We want a way to easily run a private GMainContext in a thread, with correct synchronization between startup and shutdown of the thread. Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com&gt; --- po/POTFILES.in | 1 + src/libvirt_private.syms | 5 ++ src/util/Makefile.inc.am | 2 + src/util/vireventthread.c | 175 ++++++++++++++++++++++++++++++++++++++ src/util/vireventthread.h | 31 +++++++ 5 files changed, 214 insertions(+) create mode 100644 src/util/vireventthread.c create mode 100644 src/util/vireventthread.h diff --git a/po/POTFILES.in b/po/POTFILES.in index dba0d3a12e..d49c10407a 100644 --- a/po/POTFILES.in +++ b/po/POTFILES.in @@ -238,6 +238,7 @@ @SRCDIR(a)/src/util/virerror.c @SRCDIR(a)/src/util/virerror.h @SRCDIR(a)/src/util/virevent.c +@SRCDIR(a)/src/util/vireventthread.c @SRCDIR(a)/src/util/virfcp.c @SRCDIR(a)/src/util/virfdstream.c @SRCDIR(a)/src/util/virfile.c diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms index 375e6ea000..361c9d6c13 100644 --- a/src/libvirt_private.syms +++ b/src/libvirt_private.syms @@ -1938,6 +1938,11 @@ virEventGLibRegister; virEventGLibRunOnce; +# util/vireventthread.h +virEventThreadGetContext; +virEventThreadNew; + + # util/virfcp.h virFCIsCapableRport; virFCReadRportValue; diff --git a/src/util/Makefile.inc.am b/src/util/Makefile.inc.am index fbe67090d3..35629808c9 100644 --- a/src/util/Makefile.inc.am +++ b/src/util/Makefile.inc.am @@ -65,6 +65,8 @@ UTIL_SOURCES = \ util/vireventglib.h \ util/vireventglibwatch.c \ util/vireventglibwatch.h \ + util/vireventthread.c \ + util/vireventthread.h \ util/virfcp.c \ util/virfcp.h \ util/virfdstream.c \ diff --git a/src/util/vireventthread.c b/src/util/vireventthread.c new file mode 100644 index 0000000000..aed376bc7c --- /dev/null +++ b/src/util/vireventthread.c @@ -0,0 +1,175 @@ +/* + * vireventthread.c: thread running a dedicated GMainLoop + * + * Copyright (C) 2020 Red Hat, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>;. + */ + +#include <config.h> + +#include "vireventthread.h" +#include "virthread.h" +#include "virerror.h" + +struct _virEventThread { + GObject parent; + + GCond cond; + GMutex lock; + bool running; + + GThread *thread; + GMainContext *context; + GMainLoop *loop; +}; + +G_DEFINE_TYPE(virEventThread, vir_event_thread, G_TYPE_OBJECT) + +#define VIR_FROM_THIS VIR_FROM_EVENT + +static void +vir_event_thread_finalize(GObject *object) +{ + virEventThread *evt = VIR_EVENT_THREAD(object); + + if (evt->thread) { + g_main_loop_quit(evt->loop); + g_thread_unref(evt->thread); + } + + g_main_loop_unref(evt->loop); + g_main_context_unref(evt->context); + + g_mutex_clear(&evt->lock); + g_cond_clear(&evt->cond); + + G_OBJECT_CLASS(vir_event_thread_parent_class)->finalize(object); +} + + +static void +vir_event_thread_init(virEventThread *evt) +{ + g_cond_init(&evt->cond); + g_mutex_init(&evt->lock); + evt->running = false; + evt->context = g_main_context_new(); + evt->loop = g_main_loop_new(evt->context, FALSE); +} + + +static void +vir_event_thread_class_init(virEventThreadClass *klass) +{ + GObjectClass *obj = G_OBJECT_CLASS(klass); + + obj->finalize = vir_event_thread_finalize; +} + + +static gboolean +virEventThreadNotify(void *opaque) +{ + virEventThread *evt = opaque; + + g_mutex_lock(&evt->lock); + evt->running = TRUE; + g_mutex_unlock(&evt->lock); + g_cond_signal(&evt->cond); + + return G_SOURCE_REMOVE; +} + + +static void * +virEventThreadWorker(void *opaque) +{ + virEventThread *evt = opaque; + g_autoptr(GSource) running = g_idle_source_new(); + + g_source_set_callback(running, virEventThreadNotify, evt, NULL); + + g_source_attach(running, evt->context); + + g_main_loop_run(evt->loop); + + g_main_loop_unref(evt->loop); + g_main_context_unref(evt->context);

+ + return NULL; +} + + +static int +virEventThreadStart(virEventThread *evt, const char *name) +{ + g_autoptr(GError) gerr = NULL; + g_autofree char *thname = NULL; + size_t maxname = virThreadMaxName(); + + if (maxname) + thname = g_strndup(name, maxname); + else + thname = g_strdup(name); + + if (evt->thread) { + virReportError(VIR_ERR_INTERNAL_ERROR, "%s", + _("Event thread is already running")); + return -1; + } + + g_main_loop_ref(evt->loop); + g_main_context_ref(evt->context); + + evt->thread = g_thread_try_new(thname, + virEventThreadWorker, + evt, + &gerr); + if (!evt->thread) { + g_main_loop_unref(evt->loop); + g_main_context_unref(evt->context); + virReportError(VIR_ERR_INTERNAL_ERROR, + _("Unable to start event thread: %s"), + gerr->message); + return -1; + } + + g_mutex_lock(&evt->lock); + while (!evt->running) + g_cond_wait(&evt->cond, &evt->lock); + g_mutex_unlock(&evt->lock); + + return 0; +} + + +virEventThread * +virEventThreadNew(const char *name) +{ + g_autoptr(virEventThread) evt = VIR_EVENT_THREAD(g_object_new(VIR_TYPE_EVENT_THREAD, NULL)); + + if (virEventThreadStart(evt, name) < 0) + return NULL; + + return g_steal_pointer(&evt); +} + + +GMainContext * +virEventThreadGetContext(virEventThread *evt) +{ + return evt->context; +}