Linux 内核irq_stack遍历

环境Centos 4.18.0-80.el8.x86_64

一、x86架构堆栈类型说明

https://www.kernel.org/doc/Documentation/x86/kernel-stacks

int get_stack_info(unsigned long *stack, struct task_struct *task,
		   struct stack_info *info, unsigned long *visit_mask)
{
   
	if (!stack)
		goto unknown;

	task = task ? : current;

	if (in_task_stack(stack, task, info))
		goto recursion_check;

	if (task != current)
		goto unknown;

	if (in_exception_stack(stack, info))
		goto recursion_check;

	if (in_irq_stack(stack, info))
		goto recursion_check;

	if (in_entry_stack(stack, info))
		goto recursion_check;

	goto unknown;
}
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从上述函数可以看出堆栈类型存在4种，在函数show_trace_log_lvl中有一段说明如下：

	/*
	 * Iterate through the stacks, starting with the current stack pointer.
	 * Each stack has a pointer to the next one.
	 *
	 * x86-64 can have several stacks:
	 * - task stack
	 * - interrupt stack
	 * - HW exception stacks (double fault, nmi, debug, mce)
	 * - entry stack
	 *
	 * x86-32 can have up to four stacks:
	 * - task stack
	 * - softirq stack
	 * - hardirq stack
	 * - entry stack
	 */
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x86架构中一般用寄存器sp来存在栈指针。

二、Linux 内核函数 dump_stack

在之前的文章也介绍过这个函数的作用，可以打印函数调用栈。

lib/dump_stack.c

/**
 * dump_stack - dump the current task information and its stack trace
 *
 * Architectures can override this implementation by implementing its own.
 */
#ifdef CONFIG_SMP
static atomic_t dump_lock = ATOMIC_INIT(-1);

asmlinkage __visible void dump_stack(void)
{
   
	unsigned long flags;
	int was_locked;
	int old;
	int cpu;

	/*
	 * Permit this cpu to perform nested stack dumps while serialising
	 * against other CPUs
	 */
retry:
	local_irq_save(flags);
	cpu = smp_processor_id();
	old = atomic_cmpxchg(&dump_lock, -1, cpu);
	if (old == -1) {
   
		was_locked = 0;
	} else if (old == cpu) {
   
		was_locked = 1;
	} else {
   
		local_irq_restore(flags);
		cpu_relax();
		goto retry;
	}

	__dump_stack();

	if (!was_locked)
		atomic_set(&dump_lock, -1);

	local_irq_restore(flags);
}
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|- dump_stack();	// lib/dump_stack.c
	|- __dump_stack();	// arch/x86/kernel/dumpstack.c
		|- 
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