Re: [PATCH wayland-protocols v2] Add zwp_linux_explicit_synchronization_v1
On Wed, Oct 31, 2018 at 11:59:34AM +0200, Pekka Paalanen wrote: > On Mon, 15 Oct 2018 17:16:59 +0300 > Alexandros Frantzis wrote: ... > > > > The main scenario is an early exit from some code using this > > object, in which case it will be easier to correctly synchronize proper > > destruction of any user data used by the zwp_buffer_release_v1 listener, > > when having an explicit destroy request. > > > > This isn't particular to this protocol though, it's a general > > (theoretical) concern of mine with the destroy-on-event pattern. But if > > this has worked well for wp_presentation_feedback, perhaps it's not a big > > deal. > > Hi Alf, > > I'm not sure what you mean with that concern. > > When an event destroys a protocol object, the compositor will > unconditionally destroy the wl_resource right after sending the event. > That means the server-side request listener cannot receive any messages > anymore, so any user data would be destroyed at the same time anyway. > > On client side, regardless of whether there is destroy request or not, > the client will destroy the wl_proxy. The request would only let the > compositor know that the protocol object is no more. Regardless of a > destroy request, the client side will automatically ignore any events > to the destroyed wl_proxy. That ignoring is what makes client initiated > object destruction safe in the first place. > > When the client destroys the wl_proxy, it can also free any user data > associated with it, because that will guarantee that the listeners > cannot be called anymore. > > If we have a destructor event, and the client destroys the wl_proxy > before that event is sent, then the event will simply be ignored. Once > the compositor sends the event, then both client and compositor again > agree that the protocol object no longer exists. > > wl_display has a "secret" event that tells libwayland-client when the > server has destroyed the protocol object, which makes all the above > work. > > > Thanks, > pq Hi Pekka, thanks for the detailed explanation. I was misunderstanding how destroy-on-event is expected to work. I'll update the protocol to use destroy-on-event in v5. Thanks, Alexandros ___ wayland-devel mailing list wayland-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/wayland-devel
Re: [PATCH wayland-protocols v2] Add zwp_linux_explicit_synchronization_v1
On Mon, 15 Oct 2018 17:16:59 +0300 Alexandros Frantzis wrote: > On Fri, Oct 12, 2018 at 03:24:30PM +0300, Pekka Paalanen wrote: > > Hi, > > > > this is a good specification, all my comments are clarifications or > > minor adjustments. The fundamental design looks fine to me. > > Hi Pekka, > > thanks for the review! My answers are inline. I have sent a updated > version (v3) of this proposal based on this discussion. > > > On Tue, 9 Oct 2018 18:11:22 +0300 > > Alexandros Frantzis wrote: > > > > > Signed-off-by: Alexandros Frantzis ... > > > + > > > + > > > + This object is instantiated in response to a > > > + zwp_surface_synchronization_v1 request. > > > + > > > + It provides an alternative to wl_buffer.release events, providing > > > + a unique release from a single wl_surface.commit request. The > > > release > > > + event also supports explicit synchronization, providing a fence FD > > > + where relevant for the client to synchronize against before reusing > > > + the buffer. > > > + > > > + Exactly one event, either a fenced_release or an immediate_release, > > > + will be emitted for each wl_surface.commit request. > > > + > > > + This event does not replace wl_buffer.release events; servers are > > > still > > > + required to send those events. > > > > Ok. The introduction lead me to believe otherwise, that should probably > > be worded differently. > > I have remove all mention of wl_buffer.release from the intro. > > > > + > > > + > > > + > > > + > > > +Destroy this buffer release explicit synchronization object. The > > > object > > > +may be destroyed at any time. > > > + > > > > Is it inconceivable to ever add other requests in this interface? > > I don't expect other requests to be added, this is meant as > an event-only interface. > > > Could there ever be a benefit from destroying this object before it has > > sent an event? > > The main scenario is an early exit from some code using this > object, in which case it will be easier to correctly synchronize proper > destruction of any user data used by the zwp_buffer_release_v1 listener, > when having an explicit destroy request. > > This isn't particular to this protocol though, it's a general > (theoretical) concern of mine with the destroy-on-event pattern. But if > this has worked well for wp_presentation_feedback, perhaps it's not a big > deal. Hi Alf, I'm not sure what you mean with that concern. When an event destroys a protocol object, the compositor will unconditionally destroy the wl_resource right after sending the event. That means the server-side request listener cannot receive any messages anymore, so any user data would be destroyed at the same time anyway. On client side, regardless of whether there is destroy request or not, the client will destroy the wl_proxy. The request would only let the compositor know that the protocol object is no more. Regardless of a destroy request, the client side will automatically ignore any events to the destroyed wl_proxy. That ignoring is what makes client initiated object destruction safe in the first place. When the client destroys the wl_proxy, it can also free any user data associated with it, because that will guarantee that the listeners cannot be called anymore. If we have a destructor event, and the client destroys the wl_proxy before that event is sent, then the event will simply be ignored. Once the compositor sends the event, then both client and compositor again agree that the protocol object no longer exists. wl_display has a "secret" event that tells libwayland-client when the server has destroyed the protocol object, which makes all the above work. Thanks, pq pgpkJNeHApbQI.pgp Description: OpenPGP digital signature ___ wayland-devel mailing list wayland-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/wayland-devel
Re: [PATCH wayland-protocols v2] Add zwp_linux_explicit_synchronization_v1
On Fri, Oct 12, 2018 at 03:24:30PM +0300, Pekka Paalanen wrote: > Hi, > > this is a good specification, all my comments are clarifications or > minor adjustments. The fundamental design looks fine to me. Hi Pekka, thanks for the review! My answers are inline. I have sent a updated version (v3) of this proposal based on this discussion. > On Tue, 9 Oct 2018 18:11:22 +0300 > Alexandros Frantzis wrote: > > > Signed-off-by: Alexandros Frantzis > > --- > > > > patch v1 here: https://patchwork.freedesktop.org/patch/177866/ > > Changes since patch v1: > > - Add NO_SURFACE error for zwp_surface_synchronization_v1 requests. > > - Remove restriction to destroy a zwp_surface_synchronization_v1 object > > after the associated wl_surface is destroyed. > > - Clarify which buffer the acquire fence is associated with. > > - Clarify that exactly one event, either a fenced_release or a > > immediate_release, will be emitted for each commit. > > > > Makefile.am | 1 + > > .../linux-explicit-synchronization/README | 6 + > > ...x-explicit-synchronization-unstable-v1.xml | 222 ++ > > 3 files changed, 229 insertions(+) > > create mode 100644 unstable/linux-explicit-synchronization/README > > create mode 100644 > > unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml > > + > > + > > + This object implements per-surface explicit synchronization. > > + > > + Explicit synchronization refers to co-ordination of pipelined > > Strike "Explicit"? It's odd because this starts with "explicit > synchronization refers to..." and then ends saying this is "implicit > synchronization. See below. > > + operations performed on buffers. Most GPU clients will schedule > > + an asynchronous operation to render to the buffer, then immediately > > + send the buffer to the compositor to be attached to a surface. > > Should there be a paragraph break here? See below. > > + Ensuring that the rendering operation is complete before the > > + compositor displays the buffer is an implementation detail handled > > + by either the kernel or userspace graphics driver. This is referred > > + to as 'implicit synchronization'. > > + > > + By contrast, explicit synchronization takes dma_fence objects as a > > + marker of when the asynchronous operations are complete. The fence > > + provided by the client will be waited on before the compositor > > + accesses the buffer. Conversely, in place of wl_buffer.release > > + events, the Wayland server will inform the client when the buffer > > + can be destructively accessed through a zwp_buffer_release_v1 > > + object. > > So this guarantees that no more wl_buffer.release events can be triggered > by commits that used explicit sync? See below. > > + > > + This interface cannot be instantiated multiple times for a single > > + surface, and as such should only be used by the component which > > + performs the wl_surface.attach request. Whenever control of > > > + buffer attachments is released, the releasing component should > > + ensure it destroys the zwp_surface_synchronization_v1 object. > > Is the last sentence necessary? It might confuse things as it can > easily be read as if zwp_surface_synchronization_v1 was a one-shot > thing. Ack on all of the above. In v3 I have reworded a big part of this section, taking into account the points you brought up. > > + > > + > > + > > + > > +Destroy this explicit synchronization object. > > + > > +Any fence set with set_acquire_fence in this commit cycle will > > +be invalidated in the server. > > This means that if zwp_surface_synchronization_v1 object is > destroyed before issuing wl_surface.commit, then the pending acquire > fence is discarded by the server, right? Yes, reworded to make this more clear. > > + > > +zwp_buffer_release_v1 objects created by this object are not > > affected > > +by this request. > > And after wl_surface.commit, destruction has no effect on the commit. > I have clarified this in the previous paragraph about set_acquire_fence. > > + > > + > > + > > + > > + > + summary="the fence specified by the client could not be > > imported"/> > > + > + summary="multiple fences added for a single surface commit"/> > > + > + summary="multiple releases added for a single surface > > commit"/> > > + > + summary="the associated wl_surface was destroyed"/> > > + > > + > > + > > + > > +Set the acquire fence that must be signaled before the compositor > > +may sample from the buffer attached with wl_buffer_attach. The > > fence > > +is a dma_fence kernel object. > > + > > +The acquire fence is double-buffered state, and will
Re: [PATCH wayland-protocols v2] Add zwp_linux_explicit_synchronization_v1
Hi, this is a good specification, all my comments are clarifications or minor adjustments. The fundamental design looks fine to me. On Tue, 9 Oct 2018 18:11:22 +0300 Alexandros Frantzis wrote: > Signed-off-by: Alexandros Frantzis > --- > > patch v1 here: https://patchwork.freedesktop.org/patch/177866/ > Changes since patch v1: > - Add NO_SURFACE error for zwp_surface_synchronization_v1 requests. > - Remove restriction to destroy a zwp_surface_synchronization_v1 object > after the associated wl_surface is destroyed. > - Clarify which buffer the acquire fence is associated with. > - Clarify that exactly one event, either a fenced_release or a > immediate_release, will be emitted for each commit. > > Makefile.am | 1 + > .../linux-explicit-synchronization/README | 6 + > ...x-explicit-synchronization-unstable-v1.xml | 222 ++ > 3 files changed, 229 insertions(+) > create mode 100644 unstable/linux-explicit-synchronization/README > create mode 100644 > unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml > > diff --git a/Makefile.am b/Makefile.am > index 6394e26..7dfbb9e 100644 > --- a/Makefile.am > +++ b/Makefile.am > @@ -21,6 +21,7 @@ unstable_protocols = > \ > unstable/xdg-output/xdg-output-unstable-v1.xml > \ > unstable/input-timestamps/input-timestamps-unstable-v1.xml \ > unstable/xdg-decoration/xdg-decoration-unstable-v1.xml \ > + > unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml > \ > $(NULL) > > stable_protocols = > \ > diff --git a/unstable/linux-explicit-synchronization/README > b/unstable/linux-explicit-synchronization/README > new file mode 100644 > index 000..f13b404 > --- /dev/null > +++ b/unstable/linux-explicit-synchronization/README > @@ -0,0 +1,6 @@ > +Linux explicit synchronization (dma-fence) protocol > + > +Maintainers: > +David Reveman > +Daniel Stone > +Alexandros Frantzis > diff --git > a/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml > > b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml > new file mode 100644 > index 000..11ef3f0 > --- /dev/null > +++ > b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml > @@ -0,0 +1,222 @@ > + > + > + > + > +Copyright 2016 The Chromium Authors. > +Copyright 2017 Intel Corporation > +Copyright 2018 Collabora, Ltd > + > +Permission is hereby granted, free of charge, to any person obtaining a > +copy of this software and associated documentation files (the > "Software"), > +to deal in the Software without restriction, including without limitation > +the rights to use, copy, modify, merge, publish, distribute, sublicense, > +and/or sell copies of the Software, and to permit persons to whom the > +Software is furnished to do so, subject to the following conditions: > + > +The above copyright notice and this permission notice (including the next > +paragraph) shall be included in all copies or substantial portions of the > +Software. > + > +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS > OR > +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, > +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL > +THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR > OTHER > +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING > +FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER > +DEALINGS IN THE SOFTWARE. > + > + > + > + > + This global is a factory interface, allowing clients to request > + explicit synchronization for buffers on a per-surface basis. > + > + See zwp_surface_synchronization_v1 for more information. > + > + This interface is derived from Chromium's > + zcr_linux_explicit_synchronization_v1. > + > + Warning! The protocol described in this file is experimental and > + backward incompatible changes may be made. Backward compatible changes > + may be added together with the corresponding interface version bump. > + Backward incompatible changes are done by bumping the version number in > + the protocol and interface names and resetting the interface version. > + Once the protocol is to be declared stable, the 'z' prefix and the > + version number in the protocol and interface names are removed and the > + interface version number is reset. > + > + > + > + > +Destroy this explicit synchronization factory object. Other objects, > +including zwp_surface_synchronization_v1 objects
[PATCH wayland-protocols v2] Add zwp_linux_explicit_synchronization_v1
Signed-off-by: Alexandros Frantzis --- patch v1 here: https://patchwork.freedesktop.org/patch/177866/ Changes since patch v1: - Add NO_SURFACE error for zwp_surface_synchronization_v1 requests. - Remove restriction to destroy a zwp_surface_synchronization_v1 object after the associated wl_surface is destroyed. - Clarify which buffer the acquire fence is associated with. - Clarify that exactly one event, either a fenced_release or a immediate_release, will be emitted for each commit. Makefile.am | 1 + .../linux-explicit-synchronization/README | 6 + ...x-explicit-synchronization-unstable-v1.xml | 222 ++ 3 files changed, 229 insertions(+) create mode 100644 unstable/linux-explicit-synchronization/README create mode 100644 unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml diff --git a/Makefile.am b/Makefile.am index 6394e26..7dfbb9e 100644 --- a/Makefile.am +++ b/Makefile.am @@ -21,6 +21,7 @@ unstable_protocols = \ unstable/xdg-output/xdg-output-unstable-v1.xml \ unstable/input-timestamps/input-timestamps-unstable-v1.xml \ unstable/xdg-decoration/xdg-decoration-unstable-v1.xml \ + unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml \ $(NULL) stable_protocols = \ diff --git a/unstable/linux-explicit-synchronization/README b/unstable/linux-explicit-synchronization/README new file mode 100644 index 000..f13b404 --- /dev/null +++ b/unstable/linux-explicit-synchronization/README @@ -0,0 +1,6 @@ +Linux explicit synchronization (dma-fence) protocol + +Maintainers: +David Reveman +Daniel Stone +Alexandros Frantzis diff --git a/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml new file mode 100644 index 000..11ef3f0 --- /dev/null +++ b/unstable/linux-explicit-synchronization/linux-explicit-synchronization-unstable-v1.xml @@ -0,0 +1,222 @@ + + + + +Copyright 2016 The Chromium Authors. +Copyright 2017 Intel Corporation +Copyright 2018 Collabora, Ltd + +Permission is hereby granted, free of charge, to any person obtaining a +copy of this software and associated documentation files (the "Software"), +to deal in the Software without restriction, including without limitation +the rights to use, copy, modify, merge, publish, distribute, sublicense, +and/or sell copies of the Software, and to permit persons to whom the +Software is furnished to do so, subject to the following conditions: + +The above copyright notice and this permission notice (including the next +paragraph) shall be included in all copies or substantial portions of the +Software. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL +THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING +FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. + + + + + This global is a factory interface, allowing clients to request + explicit synchronization for buffers on a per-surface basis. + + See zwp_surface_synchronization_v1 for more information. + + This interface is derived from Chromium's + zcr_linux_explicit_synchronization_v1. + + Warning! The protocol described in this file is experimental and + backward incompatible changes may be made. Backward compatible changes + may be added together with the corresponding interface version bump. + Backward incompatible changes are done by bumping the version number in + the protocol and interface names and resetting the interface version. + Once the protocol is to be declared stable, the 'z' prefix and the + version number in the protocol and interface names are removed and the + interface version number is reset. + + + + +Destroy this explicit synchronization factory object. Other objects, +including zwp_surface_synchronization_v1 objects created by this +factory, shall not be affected by this request. + + + + + + + + + +Instantiate an interface extension for the given wl_surface to +provide explicit synchronization. + +If the given wl_surface already has an explicit synchronization object +associated, the synchronization_exists protocol error is raised. + + + + + +
