diff --git a/kernel/spinlock/spinlock.c b/kernel/spinlock/spinlock.c
index c290023..0578cbb 100644
--- a/kernel/spinlock/spinlock.c
+++ b/kernel/spinlock/spinlock.c
@@ -5,17 +5,15 @@
 #include "hal/hal.h"
 #include "kprintf.h"
 
-#define SPINLOCK_IRQ_DBG 1
-
 #define SPINLOCK_HINT() asm volatile("pause")
 
 struct {
-  atomic_uint64_t irq_flags;
+  uint64_t irq_flags;
   atomic_int irq_nest;
-} IRQ_CTX;
+} IRQ_CTX = {0};
 
 void spinlock_init(SpinLock *sl) {
-  atomic_store(&sl->lock, false);
+  atomic_clear_flag_explicit(&sl->lock, memory_order_relaxed);
 }
 
 uint64_t irqsave(void) {
@@ -25,37 +23,22 @@ uint64_t irqsave(void) {
 }
 
 void irqrestore(uint64_t flags) {
-  if (flags & (1<<9)) {
+  if (flags & (1ULL << 9)) {
     asm volatile("sti" ::: "memory", "cc");
   }
 }
 
 void irqsave_nested(void) {
-  if (atomic_load(&IRQ_CTX.irq_nest) == 0) {
-    atomic_store(&IRQ_CTX.irq_flags, irqsave());
+  int prev = atomic_fetch_add_explicit(&IRQ_CTX.irq_nest, 1, memory_order_acq_rel);
+  if (prev == 0) {
+    IRQ_CTX.irq_flags = irqsave();
   }
-  atomic_inc(&IRQ_CTX.irq_nest);
-
-  #if SPINLOCK_IRQ_DBG
-    if (atomic_load(&IRQ_CTX.irq_nest) < 0) {
-      kprintf("IRQ_CTX.irq_nest underflow\n");
-      hal_hang();
-    }
-  #endif
 }
 
 void irqrestore_nested(void) {
-  #if SPINLOCK_IRQ_DBG
-    int irq_nest = atomic_load(&IRQ_CTX.irq_nest);
-    if (irq_nest <= 0) {
-      kprintf("spinlock: irqs restored too many times: %d\n", irq_nest);
-      hal_hang();
-    }
-  #endif
-
-  atomic_dec(&IRQ_CTX.irq_nest);
-  if (atomic_load(&IRQ_CTX.irq_nest) == 0) {
-    irqrestore(atomic_load(&IRQ_CTX.irq_flags));
+  int prev = atomic_fetch_sub_explicit(&IRQ_CTX.irq_nest, 1, memory_order_acq_rel);
+  if (prev == 1) {
+    irqrestore(IRQ_CTX.irq_flags);
   }
 }