On Fri, 29 Apr 2016 19:30:22 +0800 Jonas Ådahl <jad...@gmail.com> wrote:
> Using the libwayland-client client API with multiple threads with > thread local queues are prone to race conditions. > > The problem is that one thread can read and queue events after another > thread creates a proxy but before it sets the queue. > > This may result in the event to the proxy being silently dropped, or > potentially dispatched on the wrong thread had the creating thread set > the implementation before setting the queue. > > This patch introduces API to solve this case by introducing "proxy > wrappers". In short, a proxy wrapper is a wl_proxy struct that will > never itself proxy any events, but may be used by the client to set a > queue, and use it instead of the original proxy when sending requests > that creates new proxies. When sending requests, the wrapper will > work in the same way as the normal proxy object, but the proxy created > by sending a request (for example wl_display.sync) will inherit to the > same proxy queue as the wrapper. > > https://bugs.freedesktop.org/show_bug.cgi?id=91273 > > Signed-off-by: Jonas Ådahl <jad...@gmail.com> > Reviewed-by: Pekka Paalanen <pekka.paala...@collabora.co.uk> > Reviewed-by: Derek Foreman <der...@osg.samsung.com> > --- > > Changes since v3: > > - Migrated a couple of more wl_log(..); to wl_abort() that were missed in > the previous iteration. > - Removed any parent-proxy checks in the wrapper creator. > > > > src/wayland-client-core.h | 6 +++ > src/wayland-client.c | 110 > +++++++++++++++++++++++++++++++++++++++++++++- > 2 files changed, 115 insertions(+), 1 deletion(-) Hi Jonas, yup, this looks good. This and the tests v4 patch pushed: 9a652c4..69ec70f master -> master > +WL_EXPORT void * > +wl_proxy_create_wrapper(void *proxy) > +{ > + struct wl_proxy *wrapped_proxy = proxy; > + struct wl_proxy *wrapper; > + > + wrapper = zalloc(sizeof *wrapper); > + if (!wrapper) > + return NULL; > + > + pthread_mutex_lock(&wrapped_proxy->display->mutex); > + > + wrapper->object.interface = wrapped_proxy->object.interface; > + wrapper->object.id = wrapped_proxy->object.id; > + wrapper->version = wrapped_proxy->version; > + wrapper->display = wrapped_proxy->display; > + wrapper->queue = wrapped_proxy->queue; > + wrapper->flags = WL_PROXY_FLAG_WRAPPER; > + wrapper->refcount = 1; > + > + pthread_mutex_unlock(&wrapped_proxy->display->mutex); > + > + return wrapper; > +} I didn't want to postpone the landing of this any longer, but I still wonder if we really need that locking at all. Thanks, pq
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