[arch][x86] implement basic spinlocks

-This fixes the instability, seems stable on x86-64.

arch/x86/32/spinlock.S

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2025 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+#include <lk/asm.h>
+
+#if WITH_SMP
+
+// void arch_spin_lock(spin_lock_t *lock);
+FUNCTION(arch_spin_lock)
+    mov  4(%esp), %ecx
+
+    mov  $1, %edx
+0:
+    xor  %eax, %eax
+    lock cmpxchg  %edx, (%ecx)
+    jz 1f
+    pause
+    jmp 0b
+1:
+    ret
+END_FUNCTION(arch_spin_lock)
+
+// int arch_spin_trylock(spin_lock_t *lock);
+FUNCTION(arch_spin_trylock)
+    mov  4(%esp), %ecx
+
+    mov  $1, %eax
+    lock xchg  %eax, (%ecx)
+
+    ret
+END_FUNCTION(arch_spin_trylock)
+
+// void arch_spin_unlock(spin_lock_t *lock);
+FUNCTION(arch_spin_unlock)
+    mov   4(%esp), %ecx
+    movl  $0, (%ecx)
+    ret
+END_FUNCTION(arch_spin_unlock)
+
+#endif // WITH_SMP

arch/x86/64/spinlock.S

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2025 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+#include <lk/asm.h>
+
+#if WITH_SMP
+
+// void arch_spin_lock(spin_lock_t *lock);
+FUNCTION(arch_spin_lock)
+    mov  $1, %esi
+0:
+    xor  %eax, %eax
+    lock cmpxchg  %esi, (%rdi)
+    jz 1f
+    pause
+    jmp 0b
+1:
+    ret
+END_FUNCTION(arch_spin_lock)
+
+// int arch_spin_trylock(spin_lock_t *lock);
+FUNCTION(arch_spin_trylock)
+    mov  $1, %eax
+
+    lock xchg  %eax, (%rdi)
+
+    ret
+END_FUNCTION(arch_spin_trylock)
+
+// void arch_spin_unlock(spin_lock_t *lock);
+FUNCTION(arch_spin_unlock)
+    movl  $0, (%rdi)
+    ret
+END_FUNCTION(arch_spin_unlock)
+
+#endif // WITH_SMP

arch/x86/include/arch/spinlock.h

@@ -7,13 +7,16 @@
  */
 #pragma once
 
+#include <lk/compiler.h>
 #include <arch/ops.h>
 #include <arch/x86.h>
 #include <stdbool.h>
 
 #define SPIN_LOCK_INITIAL_VALUE (0)
 
-typedef unsigned long spin_lock_t;
+__BEGIN_CDECLS
+
+typedef unsigned int spin_lock_t;
 
 typedef x86_flags_t spin_lock_saved_state_t;
 typedef uint spin_lock_save_flags_t;
@@ -27,6 +30,11 @@ static inline bool arch_spin_lock_held(spin_lock_t *lock) {
     return *lock != 0;
 }
 
+#if WITH_SMP
+void arch_spin_lock(spin_lock_t *lock);
+int arch_spin_trylock(spin_lock_t *lock);
+void arch_spin_unlock(spin_lock_t *lock);
+#else
 static inline void arch_spin_lock(spin_lock_t *lock) {
     *lock = 1;
 }
@@ -38,6 +46,7 @@ static inline int arch_spin_trylock(spin_lock_t *lock) {
 static inline void arch_spin_unlock(spin_lock_t *lock) {
     *lock = 0;
 }
+#endif
 
 /* flags are unused on x86 */
 #define ARCH_DEFAULT_SPIN_LOCK_FLAG_INTERRUPTS  0
@@ -53,4 +62,4 @@ arch_interrupt_restore(spin_lock_saved_state_t old_state, spin_lock_save_flags_t
     x86_restore_flags(old_state);
 }
 
-
+__END_CDECLS

arch/x86/rules.mk

@@ -69,6 +69,7 @@ MODULE_SRCS += \
 	$(SUBARCH_DIR)/gdt.S \
 	$(SUBARCH_DIR)/mmu.c \
 	$(SUBARCH_DIR)/ops.S \
+	$(SUBARCH_DIR)/spinlock.S \
 \
 	$(LOCAL_DIR)/arch.c \
 	$(LOCAL_DIR)/cache.c \