WIP 2

kernel/spinlock/spinlock.c

@@ -5,25 +5,62 @@
 #include "hal/hal.h"
 #include "kprintf.h"
 
+#define SPINLOCK_IRQ_DBG 1
+
+#define SPINLOCK_HINT() asm volatile("pause")
+
+struct {
+  atomic_uint64_t irq_flags;
+  atomic_int irq_nest;
+} IRQ_CTX;
+
 void spinlock_init(SpinLock *sl) {
   atomic_store(&sl->lock, false);
-  sl->flags = 0;
 }
 
-uint64_t spinlock_irqsave(void) {
+uint64_t irqsave(void) {
   uint64_t flags;
-  asm volatile("pushfq; cli; popq %0" : "=r"(flags) :: "memory");
+  asm volatile("pushfq; cli; popq %0" : "=r"(flags) :: "memory", "cc");
   return flags;
 }
 
-void spinlock_irqrestore(uint64_t flags) {
+void irqrestore(uint64_t flags) {
   if (flags & (1<<9)) {
-    asm volatile("sti" ::: "memory");
+    asm volatile("sti" ::: "memory", "cc");
+  }
+}
+
+void irqsave_nested(void) {
+  if (atomic_load(&IRQ_CTX.irq_nest) == 0) {
+    atomic_store(&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));
   }
 }
 
 void spinlock_acquire(SpinLock *sl) {
-  sl->flags = spinlock_irqsave();
+  irqsave_nested();
 
   while (atomic_test_and_set_explicit(&sl->lock, memory_order_acquire)) {
     SPINLOCK_HINT();
@@ -33,6 +70,6 @@ void spinlock_acquire(SpinLock *sl) {
 void spinlock_release(SpinLock *sl) {
   atomic_clear_flag_explicit(&sl->lock, memory_order_release);
 
-  spinlock_irqrestore(sl->flags);
+  irqrestore_nested();
 }