feat atomic: added spinlock example

examples/CMakeLists.txt

@@ -8,6 +8,7 @@ add_subdirectory(allocator)
 add_subdirectory(arc4)
 add_subdirectory(array)
 add_subdirectory(ascii85)
+add_subdirectory(atomic)
 add_subdirectory(base32)
 add_subdirectory(base64)
 add_subdirectory(bfdev)

examples/atomic/.gitignore

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+/atomic-spinlock

examples/atomic/CMakeLists.txt

@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+#
+# Copyright(c) 2023 John Sanpe <sanpeqf@gmail.com>
+#
+
+add_executable(atomic-spinlock spinlock.c)
+target_link_libraries(atomic-spinlock bfdev)
+add_test(atomic-spinlock atomic-spinlock)
+
+if(${CMAKE_PROJECT_NAME} STREQUAL "bfdev")
+    install(FILES
+        spinlock.c
+        DESTINATION
+        ${CMAKE_INSTALL_DOCDIR}/examples/atomic
+    )
+
+    install(TARGETS
+        atomic-spinlock
+        DESTINATION
+        ${CMAKE_INSTALL_DOCDIR}/bin
+    )
+endif()

examples/atomic/spinlock.c

@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright(c) 2025 John Sanpe <sanpeqf@gmail.com>
+ */
+
+#define MODULE_NAME "atomic-spinlock"
+#define bfdev_log_fmt(fmt) MODULE_NAME ": " fmt
+
+#include <bfdev/atomic.h>
+#include <bfdev/cmpxchg.h>
+#include <bfdev/log.h>
+#include <pthread.h>
+#include <unistd.h>
+
+static
+bfdev_atomic_t lock;
+
+static volatile
+long counter;
+
+static void
+spin_lock(bfdev_atomic_t *lock)
+{
+    while (bfdev_cmpxchg(lock, 1, 0) != 1)
+        sched_yield();
+}
+
+static void
+spin_unlock(bfdev_atomic_t *lock)
+{
+    if (bfdev_cmpxchg(lock, 0, 1) == 0)
+        sched_yield();
+}
+
+static void *
+thread1_task(void *unused)
+{
+    unsigned int time;
+
+    for (time = 0; time < 1000000; ++time) {
+        spin_lock(&lock);
+        counter++;
+        spin_unlock(&lock);
+    }
+
+    return NULL;
+}
+
+static void *
+thread2_task(void *unused)
+{
+    unsigned int time;
+
+    for (time = 0; time < 1000000; ++time) {
+        spin_lock(&lock);
+        counter--;
+        spin_unlock(&lock);
+    }
+
+    return NULL;
+}
+
+int
+main(int argc, const char *argv[])
+{
+    pthread_t thread1, thread2;
+
+    bfdev_atomic_write(&lock, 1);
+    pthread_create(&thread1, NULL, thread1_task, NULL);
+    pthread_create(&thread2, NULL, thread2_task, NULL);
+
+    pthread_join(thread1, NULL);
+    pthread_join(thread2, NULL);
+
+    bfdev_log_info("counter: %ld\n", counter);
+    if (counter)
+        return 1;
+
+    return 0;
+}