(i.e. you shouldn't use it to flush caches explicitly if you want to e.g.
use the resource for texturing)
+Fences
+^^^^^^
+``pipe_fence_handle``, and related methods, are used to synchronize
+execution between multiple parties. Examples include CPU <-> GPU synchronization,
+renderer <-> windowing system, multiple external APIs, etc.
+
+A ``pipe_fence_handle`` can either be 'one time use' or 're-usable'. A 'one time use'
+fence behaves like a traditional GPU fence. Once it reaches the signaled state it
+is forever considered to be signaled.
+
+Once a re-usable ``pipe_fence_handle`` becomes signaled, it can be reset
+back into an unsignaled state. The ``pipe_fence_handle`` will be reset to
+the unsignaled state by performing a wait operation on said object, i.e.
+``fence_server_sync``. As a corollary to this behaviour, a re-usable
+``pipe_fence_handle`` can only have one waiter.
+
+This behaviour is useful in producer <-> consumer chains. It helps avoid
+unecessarily sharing a new ``pipe_fence_handle`` each time a new frame is
+ready. Instead, the fences are exchanged once ahead of time, and access is synchronized
+through GPU signaling instead of direct producer <-> consumer communication.
+
+``fence_server_sync`` inserts a wait command into the GPU's command stream.
+
+``fence_server_signal`` inserts a signal command into the GPU's command stream.
+
+There are no guarantees that the wait/signal commands will be flushed when
+calling ``fence_server_sync`` or ``fence_server_signal``. An explicit
+call to ``flush`` is required to make sure the commands are emitted to the GPU.
+
+The Gallium implementation may implicitly ``flush`` the command stream during a
+``fence_server_sync`` or ``fence_server_signal`` call if necessary.
Resource Busy Queries
^^^^^^^^^^^^^^^^^^^^^
void (*fence_server_sync)(struct pipe_context *pipe,
struct pipe_fence_handle *fence);
+ /**
+ * Insert commands to have the GPU signal a fence.
+ */
+ void (*fence_server_signal)(struct pipe_context *pipe,
+ struct pipe_fence_handle *fence);
+
/**
* Create a view on a texture to be used by a shader stage.
*/