From f0418655db6a344afd5c26efd04a4e4d87128233 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@tavianator.com>
Date: Wed, 28 Feb 2024 12:31:11 -0500
Subject: tests/ioq: New unit test

---
 tests/ioq.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)
 create mode 100644 tests/ioq.c

(limited to 'tests/ioq.c')

diff --git a/tests/ioq.c b/tests/ioq.c
new file mode 100644
index 0000000..3d35650
--- /dev/null
+++ b/tests/ioq.c
@@ -0,0 +1,73 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include "tests.h"
+#include "../src/ioq.h"
+#include "../src/bfstd.h"
+#include "../src/diag.h"
+#include "../src/dir.h"
+#include <errno.h>
+#include <fcntl.h>
+
+/**
+ * Test for blocking within ioq_slot_push().
+ *
+ * struct ioqq only supports non-blocking reads; if a write encounters a full
+ * slot, it must block until someone pops from that slot:
+ *
+ *     Reader                        Writer
+ *     ──────────────────────────    ─────────────────────────
+ *                                   tail:         0 → 1
+ *                                   slots[0]: empty → full
+ *                                   tail:         1 → 0
+ *                                   slots[1]: empty → full
+ *                                   tail:         0 → 1
+ *                                   slots[0]:  full → full*    (IOQ_BLOCKED)
+ *                                   ioq_slot_wait() ...
+ *     head:         0 → 1
+ *     slots[0]: full* → empty
+ *     ioq_slot_wake()
+ *                                   ...
+ *                                   slots[0]: empty → full
+ *
+ * To reproduce this unlikely scenario, we must fill up the ready queue, then
+ * call ioq_cancel() which pushes an additional sentinel IOQ_STOP operation.
+ */
+static void check_ioq_push_block(void) {
+	// Must be a power of two to fill the entire queue
+	const size_t depth = 2;
+
+	struct ioq *ioq = ioq_create(depth, 1);
+	bfs_verify(ioq, "ioq_create(): %s", xstrerror(errno));
+
+	// Push enough operations to fill the queue
+	for (size_t i = 0; i < depth; ++i) {
+		struct bfs_dir *dir = bfs_allocdir();
+		bfs_verify(dir, "bfs_allocdir(): %s", xstrerror(errno));
+
+		int ret = ioq_opendir(ioq, dir, AT_FDCWD, ".", 0, NULL);
+		bfs_verify(ret == 0, "ioq_opendir(): %s", xstrerror(errno));
+	}
+	bfs_verify(ioq_capacity(ioq) == 0);
+
+	// Now cancel the queue, pushing an additional IOQ_STOP message
+	ioq_cancel(ioq);
+
+	// Drain the queue
+	struct ioq_ent *ent;
+	while ((ent = ioq_pop(ioq, true))) {
+		bfs_verify(ent->op == IOQ_OPENDIR);
+		if (ent->result >= 0) {
+			bfs_closedir(ent->opendir.dir);
+		}
+		free(ent->opendir.dir);
+		ioq_free(ioq, ent);
+	}
+
+	ioq_destroy(ioq);
+}
+
+bool check_ioq(void) {
+	check_ioq_push_block();
+	return true;
+}
-- 
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