i think it works

code/kernel/ke_semaphore.c

@@ -0,0 +1,64 @@
+// ke_semaphore.c - counting semaphore
+#include "ke_semaphore.h"
+#include "ke_thread.h"
+#include "ke_sched.h"
+#include "ob_object.h"
+
+static void SemDestroy(OBJECT* obj) { (void)obj; }
+
+KSTATUS SemaphoreCreate(int32_t initial, int32_t max, SEMAPHORE **out) {
+    if (!out || initial < 0 || max < 1 || initial > max)
+        return STATUS_INVALID_PARAMETER;
+    SEMAPHORE* s = (SEMAPHORE *)ObAllocateObject(ObjectTypeSemaphore, sizeof(SEMAPHORE));
+    if (!s) return STATUS_NO_MEMORY;
+    s->Header.Destroy = SemDestroy;
+    s->Lock     = (SPINLOCK)SPINLOCK_INIT;
+    s->Count    = initial;
+    s->MaxCount = max;
+    LIST_INIT(&s->WaitList);
+    *out = s;
+    return STATUS_SUCCESS;
+}
+
+KSTATUS KeWaitSemaphore(SEMAPHORE* sem) {
+    if (!sem) return STATUS_INVALID_PARAMETER;
+    THREAD* self = KeCurrentThread();
+
+    for (;;) {
+        KeAcquireSpinlock(&sem->Lock);
+        if (sem->Count > 0) {
+            sem->Count--;
+            KeReleaseSpinlock(&sem->Lock);
+            return STATUS_SUCCESS;
+        }
+        ListInsertTail(&sem->WaitList, &self->SchedulerLink);
+        KeReleaseSpinlock(&sem->Lock);
+        KeBlockThread(self, &sem->Header);
+    }
+}
+
+KSTATUS KeTrySemaphore(SEMAPHORE* sem) {
+    if (!sem) return STATUS_INVALID_PARAMETER;
+    KeAcquireSpinlock(&sem->Lock);
+    if (sem->Count > 0) {
+        sem->Count--;
+        KeReleaseSpinlock(&sem->Lock);
+        return STATUS_SUCCESS;
+    }
+    KeReleaseSpinlock(&sem->Lock);
+    return STATUS_FAILURE;
+}
+
+void KeSignalSemaphore(SEMAPHORE* sem) {
+    if (!sem) return;
+    KeAcquireSpinlock(&sem->Lock);
+    if (!LIST_IS_EMPTY(&sem->WaitList)) {
+        LIST_ENTRY* node = ListPopHead(&sem->WaitList);
+        THREAD* waiter   = CONTAINING_RECORD(node, THREAD, SchedulerLink);
+        KeReleaseSpinlock(&sem->Lock);
+        KeUnblockThread(waiter);
+        return;
+    }
+    if (sem->Count < sem->MaxCount) sem->Count++;
+    KeReleaseSpinlock(&sem->Lock);
+}