Add a thread pool implementation to libutil

The thread pool enforces ordering of items during dequeue similar
to the already existing implementation in libsqfs. The idea is to
eventually pull this functionality out of the block processor and
turn it into a cleaner, separately tested module.

The thread pool is implemented as an abstract interface, so we can
have multiple implementations around, including the serial fallback
implementation which we can then *always* test, irregardless of the
compile config and run through static analysis as well.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

2 files changed, 116 insertions, 1 deletions

diff --git a/tests/libutil/Makemodule.am b/tests/libutil/Makemodule.am
index 1153db4..1fe4ebf 100644
--- a/tests/libutil/Makemodule.am
+++ b/tests/libutil/Makemodule.am
@@ -8,8 +8,12 @@ test_rbtree_LDADD = libutil.a libcompat.a
 test_xxhash_SOURCES = tests/libutil/xxhash.c
 test_xxhash_LDADD = libutil.a libcompat.a
 
+test_threadpool_SOURCES = tests/libutil/threadpool.c
+test_threadpool_CFLAGS = $(AM_CFLAGS) $(PTHREAD_CFLAGS)
+test_threadpool_LDADD = libutil.a libcompat.a $(PTHREAD_LIBS)
+
 LIBUTIL_TESTS = \
-	test_str_table test_rbtree test_xxhash
+	test_str_table test_rbtree test_xxhash test_threadpool
 
 check_PROGRAMS += $(LIBUTIL_TESTS)
 TESTS += $(LIBUTIL_TESTS)
diff --git a/tests/libutil/threadpool.c b/tests/libutil/threadpool.c
new file mode 100644
index 0000000..566239f
--- /dev/null
+++ b/tests/libutil/threadpool.c
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: LGPL-3.0-or-later */
+/*
+ * threadpool.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "threadpool.h"
+#include "../test.h"
+
+#if defined(_WIN32) || defined(__WINDOWS__)
+#define WIN32_LEAN_AND_MEAN
+#define VC_EXTRALEAN
+#include <windows.h>
+#endif
+
+#include <time.h>
+
+static int worker(void *user, void *work_item)
+{
+	unsigned int value = *((unsigned int *)work_item);
+	(void)user;
+
+#if defined(_WIN32) || defined(__WINDOWS__)
+	Sleep(100 * value);
+#else
+	{
+		struct timespec sp;
+
+		sp.tv_sec = value / 10;
+		sp.tv_nsec = 100000000;
+		sp.tv_nsec *= (long)(value % 10);
+
+		nanosleep(&sp, NULL);
+	}
+#endif
+
+	*((unsigned int *)work_item) = 42;
+	return 0;
+}
+
+int main(void)
+{
+	unsigned int values[10];
+	thread_pool_t *pool;
+	unsigned int *ptr;
+	size_t i, count;
+	int ret;
+
+	pool = thread_pool_create(10, worker);
+	TEST_NOT_NULL(pool);
+
+	count = pool->get_worker_count(pool);
+	TEST_ASSERT(count >= 1);
+
+	/* dequeue on empty pool MUST NOT deadlock */
+	ptr = pool->dequeue(pool);
+	TEST_NULL(ptr);
+
+	for (i = 0; i < sizeof(values) / sizeof(values[0]); ++i) {
+		values[i] = sizeof(values) / sizeof(values[0]) - i;
+
+		ret = pool->submit(pool, values + i);
+		TEST_EQUAL_I(ret, 0);
+	}
+
+	for (i = 0; i < sizeof(values) / sizeof(values[0]); ++i) {
+		ptr = pool->dequeue(pool);
+
+		TEST_NOT_NULL(ptr);
+		TEST_ASSERT(ptr == (values + i));
+		TEST_EQUAL_UI(*ptr, 42);
+	}
+
+	ptr = pool->dequeue(pool);
+	TEST_NULL(ptr);
+
+	pool->destroy(pool);
+
+	/* redo the same test with the serial implementation */
+	pool = thread_pool_create_serial(worker);
+	TEST_NOT_NULL(pool);
+
+	ptr = pool->dequeue(pool);
+	TEST_NULL(ptr);
+
+	count = pool->get_worker_count(pool);
+	TEST_EQUAL_UI(count, 1);
+
+	for (i = 0; i < sizeof(values) / sizeof(values[0]); ++i) {
+		values[i] = sizeof(values) / sizeof(values[0]) - i;
+
+		ret = pool->submit(pool, values + i);
+		TEST_EQUAL_I(ret, 0);
+	}
+
+	for (i = 0; i < sizeof(values) / sizeof(values[0]); ++i) {
+		ptr = pool->dequeue(pool);
+
+		TEST_NOT_NULL(ptr);
+		TEST_ASSERT(ptr == (values + i));
+		TEST_EQUAL_UI(*ptr, 42);
+	}
+
+	ptr = pool->dequeue(pool);
+	TEST_NULL(ptr);
+
+	pool->destroy(pool);
+	return EXIT_SUCCESS;
+}