94f2d7b5

vk_sync: fail closed on unknown acquire result + comments

a73x 2026-04-18 12:32

Commit message

vk_sync: fail closed on unknown acquire result + comments

Fixes from code review of the prior vk_sync commit:
- acquireImageBounded returns error.VkAcquireTimeout on unknown
  VkResult values (fails closed instead of trusting image_index).
- Document benign TOCTOU in logVkTimeout rate-limit.
- Clarify why TimeoutKind.atlas exists (reserved for Task 3).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/vk_sync.zig

Old		New
@@ -52,7 +52,10 @@ pub fn acquireImageBounded(
52	.timeout, .not_ready => return error.VkAcquireTimeout,	52	.timeout, .not_ready => return error.VkAcquireTimeout,
53	.suboptimal_khr => return error.OutOfDateKHR,	53	.suboptimal_khr => return error.OutOfDateKHR,
54	.success => return acquire.image_index,	54	.success => return acquire.image_index,
55	else => return acquire.image_index, // unexpected but non-error; trust the image_index	55	else => {
		56	std.log.warn("acquireImageBounded: unexpected VkResult {s}", .{@tagName(acquire.result)});
		57	return error.VkAcquireTimeout;
		58	},
56	}	59	}
57	}	60	}
58		61
@@ -88,7 +91,11 @@ pub fn queueWaitIdleBounded(vkd: vk.DeviceWrapper, queue: vk.Queue, timeout_ns:
88		91
89	// --- logging ---	92	// --- logging ---
90		93
91	const TimeoutKind = enum { fence, acquire, atlas };	94	const TimeoutKind = enum {
		95	fence, // waitFenceBounded timeouts
		96	acquire, // acquireImageBounded timeouts
		97	atlas, // uploadAtlasRegion fence timeouts (used by renderer.zig, Task 3)
		98	};
92		99
93	var vk_timeout_count: std.atomic.Value(u64) = .init(0);	100	var vk_timeout_count: std.atomic.Value(u64) = .init(0);
94	var last_log_ns: std.atomic.Value(i64) = .init(0);	101	var last_log_ns: std.atomic.Value(i64) = .init(0);
@@ -100,6 +107,7 @@ pub fn logVkTimeout(src: std.builtin.SourceLocation, kind: TimeoutKind) void {
100	const now: i64 = @truncate(std.time.nanoTimestamp());	107	const now: i64 = @truncate(std.time.nanoTimestamp());
101	const last = last_log_ns.load(.monotonic);	108	const last = last_log_ns.load(.monotonic);
102	if (n == 1 or (now - last) > log_window_ns) {	109	if (n == 1 or (now - last) > log_window_ns) {
		110	// Benign TOCTOU: two threads racing can fire twice in the same window.
103	last_log_ns.store(now, .monotonic);	111	last_log_ns.store(now, .monotonic);
104	std.log.warn(	112	std.log.warn(
105	"vk timeout #{} ({s}) at {s}:{d} — driver may be wedged",	113	"vk timeout #{} ({s}) at {s}:{d} — driver may be wedged",