1 files changed, 77 insertions, 0 deletions
diff --git a/tests/ioq.c b/tests/ioq.c
new file mode 100644
index 0000000..ef5ee3b
--- /dev/null
+++ b/tests/ioq.c
@@ -0,0 +1,77 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+#include "prelude.h"
+#include "tests.h"
+#include "ioq.h"
+#include "bfstd.h"
+#include "diag.h"
+#include "dir.h"
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.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
+	for (size_t i = 0; i < depth; ++i) {
+		struct ioq_ent *ent = ioq_pop(ioq, true);
+		bfs_verify(ent && ent->op == IOQ_OPENDIR);
+
+		if (ent->result >= 0) {
+			bfs_closedir(ent->opendir.dir);
+		}
+		free(ent->opendir.dir);
+		ioq_free(ioq, ent);
+	}
+	bfs_verify(!ioq_pop(ioq, true));
+
+	ioq_destroy(ioq);
+}
+
+bool check_ioq(void) {
+	check_ioq_push_block();
+	return true;
+}