Ichthyostega
703e60c85a
''Review supported by Claude Code'' Control flow logic was scrutinised, and a race identified in the solution to pass on the display action to the GUI thread. Reconsidering the design, cross-thread synchronisation is now hinged rather on a single atomic buffer pointer, where the GUI thread notifies back completion of display work by setting that pointer to NULL. Overall this simplifies the control logic ---- As an aside, I setup an outline of topics for documentation in `DemoSpec.txt` and then instructed Claude to fill in the paragraphs, based on insight gained as part of the code validation / review. Furthermore, I requested to generate some diagrams that could be useful later when preparting the presentation
56 lines
2.3 KiB
Text
56 lines
2.3 KiB
Text
// Cross-thread architecture and data-visibility handoff.
|
|
// Render: dot -Tsvg thread-handoff.dot -o thread-handoff.svg
|
|
//
|
|
// One direction of data flow: the Proactor thread reads file blocks into the
|
|
// ring of buffers and publishes a ready frame through the single atomic baton
|
|
// `toDisplay_`; the GUI thread picks it up, uploads it to the GPU, and hands
|
|
// the slot back. The release/acquire pairs on the baton carry buffer-content
|
|
// visibility in both directions.
|
|
|
|
digraph handoff {
|
|
rankdir=LR;
|
|
bgcolor="transparent";
|
|
compound=true;
|
|
fontname="sans-serif";
|
|
node [fontname="sans-serif", fontsize=11];
|
|
edge [fontname="sans-serif", fontsize=10];
|
|
|
|
file [shape=cylinder, fillcolor="#eeeeee", style=filled, label="demovideo.raw"];
|
|
|
|
subgraph cluster_proactor {
|
|
label=" »Proactor« thread — playVideo() loop ";
|
|
labeljust="l";
|
|
style="filled,rounded"; fillcolor="#eef4ff"; color="#7092c0"; fontsize=12;
|
|
|
|
wait [shape=box, style="rounded,filled", fillcolor="#ffffff",
|
|
label="io_uring_wait_cqe()\n(blocking)"];
|
|
timer [shape=box, style="rounded,filled", fillcolor="#ffedcc",
|
|
label="frame-beat timer\n20 ms · multishot"];
|
|
ring [shape=record, style=filled, fillcolor="#ffffff",
|
|
label="ring buffers\ (RING_SIZ)|<s0>slot|<s1>slot|<s2>slot|<s3>…"];
|
|
}
|
|
|
|
subgraph cluster_gui {
|
|
label=" GTK / GUI thread ";
|
|
labeljust="l";
|
|
style="filled,rounded"; fillcolor="#eefaee"; color="#6bab6b"; fontsize=12;
|
|
|
|
disp [shape=box, style="rounded,filled", fillcolor="#ffffff",
|
|
label="EglDisplay::displayFrame()\nretrieveFrame() / completedFrame()"];
|
|
gpu [shape=box, style="rounded,filled", fillcolor="#ffffff",
|
|
label="GPU texture\n(glTexImage2D → draw)"];
|
|
}
|
|
|
|
baton [shape=box, style="filled", fillcolor="#e7d8ff", penwidth=1.6,
|
|
label="toDisplay_\nstd::atomic<Buffer*>"];
|
|
|
|
file -> ring [label="io_uring read", lhead=cluster_proactor];
|
|
timer -> wait [style=dotted, label="CQE (TICK_TAG)"];
|
|
ring -> baton [label="publish\nstore(release)", color="#5a2ca0", fontcolor="#5a2ca0"];
|
|
baton -> disp [label="retrieveFrame\nload(acquire)", color="#5a2ca0", fontcolor="#5a2ca0"];
|
|
disp -> gpu [label="upload + draw"];
|
|
disp -> baton [label="completedFrame\nstore(nullptr, release)",
|
|
style=dashed, color="#3a7a3a", fontcolor="#3a7a3a"];
|
|
|
|
{ rank=same; baton; }
|
|
}
|