diff --git a/Makefile b/Makefile
index e99f2a0..b3e8f6c 100644
--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,7 @@ all: kern/kernel.elf
 
 main: main.o
 
-kern/kernel.elf: kern/entry.o kern/start.o kern/libkern/string.o kern/libkern/proc.o kern/libkern/uart.o kern/libkern/panic.o kern/kalloc.o kern/libkern/memory.o kern/libkern/spinlock.o kern/libkern/string.o kern/libkern/mini-printf.o
+kern/kernel.elf: kern/entry.o kern/start.o kern/libkern/string.o kern/libkern/proc.o kern/libkern/uart.o kern/libkern/panic.o kern/kalloc.o kern/libkern/memory.o kern/ispinlock.o kern/libkern/spinlock.o kern/libkern/string.o kern/libkern/mini-printf.o
 	@echo LD $@
 	@$(LD) $(LDFLAGS) -o $@ $^
 
diff --git a/kern/ispinlock.c b/kern/ispinlock.c
new file mode 100644
index 0000000..01965f8
--- /dev/null
+++ b/kern/ispinlock.c
@@ -0,0 +1,45 @@
+#include "ispinlock.h"
+
+void spinlock_init(spinlock_t *l) {
+    l->v = 0;
+}
+
+__attribute__((warn_unused_result)) bool spin_trylock(spinlock_t *l) {
+    uint32_t old;
+    // old = xchg_acquire(&l->v, 1) using AMO
+    __asm__ volatile("amoswap.w.aq %0, %2, (%1)\n" : "=&r"(old) : "r"(&l->v), "r"(1u) : "memory");
+    return old == 0;
+}
+
+void spin_unlock(spinlock_t *l) {
+    // Release: store 0 with .rl ordering.
+    uint32_t dummy;
+    __asm__ volatile("amoswap.w.rl %0, %2, (%1)\n" : "=&r"(dummy) : "r"(&l->v), "r"(0u) : "memory");
+}
+
+// Optional: tiny pause/backoff (works even if Zihintpause isn't present).
+// See: https://github.com/riscv/riscv-isa-manual/blob/main/src/zihintpause.adoc
+static inline void cpu_relax(void) {
+#if defined(__riscv_zihintpause)
+    __asm__ volatile("pause");
+#else
+    __asm__ volatile("nop");
+#endif
+}
+
+// Test-and-test-and-set acquire with polite spinning + exponential backoff.
+void spin_lock(spinlock_t *l) {
+    unsigned backoff = 1;
+    for (;;) {
+        if (spin_trylock(l))
+            return;
+
+        // Contended: spin on plain loads (no AMO) until it looks free.
+        while (__atomic_load_n(&l->v, __ATOMIC_RELAXED) != 0) {
+            for (unsigned i = 0; i < backoff; ++i) cpu_relax();
+            if (backoff < 1u << 12)
+                backoff <<= 1;
+        }
+        // Try again; loop.
+    }
+}
diff --git a/kern/ispinlock.h b/kern/ispinlock.h
new file mode 100644
index 0000000..e30d4b6
--- /dev/null
+++ b/kern/ispinlock.h
@@ -0,0 +1,11 @@
+#pragma once
+#include <stdint.h>
+
+typedef struct {
+    volatile uint32_t v; // 0 = unlocked, 1 = locked
+} spinlock_t;
+
+void spinlock_init(spinlock_t *l);
+bool spin_trylock(spinlock_t *l);
+void spin_unlock(spinlock_t *l);
+void spin_lock(spinlock_t *l);
diff --git a/kern/kalloc.c b/kern/kalloc.c
index b0f89a0..0adbdc9 100644
--- a/kern/kalloc.c
+++ b/kern/kalloc.c
@@ -1,4 +1,4 @@
-#include <spinlock.h>
+#include <ispinlock.h>
 #include <kalloc.h>
 #include <memory.h>
 #include <panic.h>
diff --git a/kern/libkern/spinlock.c b/kern/libkern/spinlock.c
index f3b194a..6b1d89f 100644
--- a/kern/libkern/spinlock.c
+++ b/kern/libkern/spinlock.c
@@ -122,47 +122,3 @@ void pop_off(void) {
     if (c->noff == 0 && c->intena)
         intr_on();
 }
-
-void spinlock_init(spinlock_t *l) {
-    l->v = 0;
-}
-
-__attribute__((warn_unused_result)) bool spin_trylock(spinlock_t *l) {
-    uint32_t old;
-    // old = xchg_acquire(&l->v, 1) using AMO
-    __asm__ volatile("amoswap.w.aq %0, %2, (%1)\n" : "=&r"(old) : "r"(&l->v), "r"(1u) : "memory");
-    return old == 0;
-}
-
-void spin_unlock(spinlock_t *l) {
-    // Release: store 0 with .rl ordering.
-    uint32_t dummy;
-    __asm__ volatile("amoswap.w.rl %0, %2, (%1)\n" : "=&r"(dummy) : "r"(&l->v), "r"(0u) : "memory");
-}
-
-// Optional: tiny pause/backoff (works even if Zihintpause isn't present).
-// See: https://github.com/riscv/riscv-isa-manual/blob/main/src/zihintpause.adoc
-static inline void cpu_relax(void) {
-#if defined(__riscv_zihintpause)
-    __asm__ volatile("pause");
-#else
-    __asm__ volatile("nop");
-#endif
-}
-
-// Test-and-test-and-set acquire with polite spinning + exponential backoff.
-void spin_lock(spinlock_t *l) {
-    unsigned backoff = 1;
-    for (;;) {
-        if (spin_trylock(l))
-            return;
-
-        // Contended: spin on plain loads (no AMO) until it looks free.
-        while (__atomic_load_n(&l->v, __ATOMIC_RELAXED) != 0) {
-            for (unsigned i = 0; i < backoff; ++i) cpu_relax();
-            if (backoff < 1u << 12)
-                backoff <<= 1;
-        }
-        // Try again; loop.
-    }
-}
diff --git a/kern/libkern/spinlock.h b/kern/libkern/spinlock.h
index 5561b98..9629e60 100644
--- a/kern/libkern/spinlock.h
+++ b/kern/libkern/spinlock.h
@@ -48,13 +48,4 @@ void push_off(void);
 /** @copydoc pop_off */
 void pop_off(void);
 
-typedef struct {
-    volatile uint32_t v; // 0 = unlocked, 1 = locked
-} spinlock_t;
-
-void spinlock_init(spinlock_t *l);
-bool spin_trylock(spinlock_t *l);
-void spin_unlock(spinlock_t *l);
-void spin_lock(spinlock_t *l);
-
 #endif
diff --git a/kern/libkern/stdint.h b/kern/libkern/stdint.h
index 69e74d4..37c912f 100644
--- a/kern/libkern/stdint.h
+++ b/kern/libkern/stdint.h
@@ -13,4 +13,4 @@ typedef uint64_t       size_t;
 
 typedef uint64_t uintptr_t;
 
-typedef u8 bool;
+// typedef u8 bool;
diff --git a/kern/start.c b/kern/start.c
index 0a34508..10503d1 100644
--- a/kern/start.c
+++ b/kern/start.c
@@ -1,5 +1,5 @@
 #include <config.h>
-#include <spinlock.h>
+#include <ispinlock.h>
 #include <kalloc.h>
 #include <memory.h>
 #include <proc.h>