On 08/07/2016 10:54, Daniel P. Berrange wrote: > On Fri, Jul 08, 2016 at 09:48:23AM +0800, Fam Zheng wrote: >> On Wed, 06/22 18:49, Zhang Chen wrote: >>> We want to poll and handle chardev in another thread >>> other than main loop. But qemu_chr_add_handlers() can only >>> work for global default context other than thread default context. >>> So we use g_source_attach(xx, g_main_context_get_thread_default()) >>> replace g_source_attach(xx, NULL) to attach g_source. >>> Comments from jason. >>> >>> Signed-off-by: Zhang Chen <zhangchen.f...@cn.fujitsu.com> >>> Signed-off-by: Jason Wang <jasow...@redhat.com> >>> --- >>> io/channel.c | 2 +- >>> qemu-char.c | 6 +++--- >>> 2 files changed, 4 insertions(+), 4 deletions(-) >>> >>> diff --git a/io/channel.c b/io/channel.c >>> index 692eb17..cd25677 100644 >>> --- a/io/channel.c >>> +++ b/io/channel.c >>> @@ -146,7 +146,7 @@ guint qio_channel_add_watch(QIOChannel *ioc, >>> >>> g_source_set_callback(source, (GSourceFunc)func, user_data, notify); >>> >>> - id = g_source_attach(source, NULL); >>> + id = g_source_attach(source, g_main_context_get_thread_default()); >>> g_source_unref(source); >>> >>> return id; >>> diff --git a/qemu-char.c b/qemu-char.c >>> index 84f49ac..4340457 100644 >>> --- a/qemu-char.c >>> +++ b/qemu-char.c >>> @@ -859,7 +859,7 @@ static gboolean io_watch_poll_prepare(GSource *source, >>> gint *timeout_) >>> iwp->src = qio_channel_create_watch( >>> iwp->ioc, G_IO_IN | G_IO_ERR | G_IO_HUP | G_IO_NVAL); >>> g_source_set_callback(iwp->src, iwp->fd_read, iwp->opaque, NULL); >>> - g_source_attach(iwp->src, NULL); >>> + g_source_attach(iwp->src, g_main_context_get_thread_default()); >>> } else { >>> g_source_destroy(iwp->src); >>> g_source_unref(iwp->src); >>> @@ -918,7 +918,7 @@ static guint io_add_watch_poll(QIOChannel *ioc, >>> iwp->fd_read = (GSourceFunc) fd_read; >>> iwp->src = NULL; >>> >>> - tag = g_source_attach(&iwp->parent, NULL); >>> + tag = g_source_attach(&iwp->parent, >>> g_main_context_get_thread_default()); >>> g_source_unref(&iwp->parent); >>> return tag; >>> } >>> @@ -3982,7 +3982,7 @@ int qemu_chr_fe_add_watch(CharDriverState *s, >>> GIOCondition cond, >>> } >>> >>> g_source_set_callback(src, (GSourceFunc)func, user_data, NULL); >>> - tag = g_source_attach(src, NULL); >>> + tag = g_source_attach(src, g_main_context_get_thread_default()); >>> g_source_unref(src); >>> >>> return tag; >>> -- >> >> IIRC this opens a gate for your special thread (COLO compare thread?) to use >> QIOChannel. > > I've no real objection to this proposed patch, though it is fairly pointless > to take it now without seeing any following patch that actually makes use > of this added feature.
I agree. >> I think in the long run it is better to think about allowing integrating QIO >> to >> AioContext, to support its usage outside main loop. Given how opaque GSource >> is, I'm not sure how feasible that is, or how useful it will be. Anyway we >> should definitely hear more opinions from Daniel and Paolo. > > Personally I think it is preferable to stick as close to the standard GSource > model as possible, as that's widely used & well understood API, compared to > the > QEMU specific AioContext. AioContext is more optimized for the case where the callbacks are static. In general this is not the case for qemu-char.c. Paolo