Update submodules

linux/内核-驱动/中断/__raise_softirq.md → linux/内核-驱动/中断/软中断--__raise_softirq.md

@@ -8,7 +8,7 @@ tags:
 
 ```c
 #ifndef local_softirq_pending_ref
-#define local_softirq_pending_ref irq_stat.__softirq_pending
+#define local_softirq_pending_ref irq_stat.__softirq_pending //软中断挂起位图，每bit代表一种软中断
 #endif
 
 #define local_softirq_pending()	(__this_cpu_read(local_softirq_pending_ref))

linux/内核-驱动/中断/软中断--ksoftirqd.md

@@ -0,0 +1,57 @@
+---
+title: ksoftirqd 分析
+date: 2024-11-20 14:46:23
+tags:
+---
+
+# ksoftirqd 结构
+```c
+static struct smp_hotplug_thread softirq_threads = {
+	.store			= &ksoftirqd,
+	.thread_should_run	= ksoftirqd_should_run,
+	.thread_fn		= run_ksoftirqd,
+	.thread_comm		= "ksoftirqd/%u",
+};
+
+static void run_ksoftirqd(unsigned int cpu)
+{
+	ksoftirqd_run_begin(); // 关闭cpu 中断响应
+	if (local_softirq_pending()) {
+		/*
+		 * We can safely run softirq on inline stack, as we are not deep
+		 * in the task stack here.
+		 */
+		__do_softirq();
+		ksoftirqd_run_end();
+		cond_resched();
+		return;
+	}
+	ksoftirqd_run_end();  // 开启cpu 中断响应
+}
+```
+
+# ksoftirqd的调度
+内核本身不会主动周期性的调度softirqd，一般是通过驱动模块或者第三方事件触发：
+内核中有三个地方调用wakeup_softirqd唤醒ksoftirqd内核线程：
+1. 在__do_softirq函数中
+2. 在raise_softirq_irqoff函数中
+3. 在invoke_softirq函数中
+
+```c
+static inline void __irq_exit_rcu(void)
+{
+#ifndef __ARCH_IRQ_EXIT_IRQS_DISABLED
+	local_irq_disable(); // 保证硬中断退出时的原子性
+#else
+	lockdep_assert_irqs_disabled();
+#endif
+	account_hardirq_exit(current);
+    // 退出硬中断上下文
+	preempt_count_sub(HARDIRQ_OFFSET);
+    // 避免了在软中断环境下的硬中断断，导致的softirqd被多次调度，也就是说如果硬中断发生在当前cpu 的软中断环境下那么该硬中断在退出时不会触发软中断
+	if (!in_interrupt() && local_softirq_pending())
+		invoke_softirq();
+
+	tick_irq_exit();
+}
+```

linux/内核-驱动/中断/软中断--wakeup_softirqd.md

@@ -0,0 +1,10 @@
+```c
+static void wakeup_softirqd(void)
+{
+	/* Interrupts are disabled: no need to stop preemption */
+	struct task_struct *tsk = __this_cpu_read(ksoftirqd);
+
+	if (tsk)
+		wake_up_process(tsk);
+}
+```

linux/内核-驱动/中断/软中断进入接口.md → linux/内核-驱动/中断/软中断--上下文切换接口.md

@@ -1,5 +1,5 @@
 ---
-title: 软中断进入接口
+title: 软中断上下文切换接口
 date: 2024-11-20 14:46:23
 tags:
 ---