preempt/irq：计数式中断开关 + NMI 位域迁出（Rust SpinLockIrq 系列 v4 进展更新）

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index d57cab4d4c06..8d4895531a45 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -10,6 +10,8 @@
 #include <linux/vtime.h>
 #include <asm/hardirq.h>
 
+DECLARE_PER_CPU(unsigned int, nmi_nesting);
+
 extern void synchronize_irq(unsigned int irq);
 extern bool synchronize_hardirq(unsigned int irq);
 
@@ -102,14 +104,17 @@ void irq_exit_rcu(void);
  */
 
 /*
- * nmi_enter() can nest up to 15 times; see NMI_BITS.
+ * nmi_enter() can nest - nesting is tracked in a per-CPU counter.
  */
 #define __nmi_enter()						\
 	do {							\
 		lockdep_off();					\
 		arch_nmi_enter();				\
-		BUG_ON(in_nmi() == NMI_MASK);			\
-		__preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET);	\
+		/* Maximum NMI nesting is 15. */		\
+		BUG_ON(__this_cpu_read(nmi_nesting) >= 15);	\
+		__this_cpu_inc(nmi_nesting);			\
+		__preempt_count_add(HARDIRQ_OFFSET);		\
+		preempt_count_set(preempt_count() | NMI_MASK);	\
 	} while (0)

diff --git a/include/linux/interrupt_rc.h b/include/linux/interrupt_rc.h
new file mode 100644
index 000000000000..b9a7f05ecf42
--- /dev/null
+++ b/include/linux/interrupt_rc.h
@@ -0,0 +1,82 @@
+static inline void local_interrupt_disable(void)
+{
+	int new_count;
+
+	WARN_ON_ONCE(in_nmi());
+
+	new_count = hardirq_disable_enter();
+
+	/* Interrupts can happen here, but it's OK, see __irq_exit_rcu(). */
+
+	if ((new_count & HARDIRQ_DISABLE_MASK) == HARDIRQ_DISABLE_OFFSET)
+		_local_interrupt_disable();
+}
+
+static inline void local_interrupt_enable(void)
+{
+	int new_count;
+
+	new_count = hardirq_disable_exit();
+
+	if ((new_count & HARDIRQ_DISABLE_MASK) == 0)
+		_local_interrupt_enable();
+}