// SPDX-License-Identifier: GPL-2.0/* * Provide a default dump_stack() function for architectures * which don't implement their own. */ #include <linux/kernel.h>#include <linux/export.h>#include <linux/sched.h>#include <linux/sched/debug.h>#include <linux/smp.h>#include <linux/atomic.h> static void __dump_stack(void){	dump_stack_print_info(KERN_DEFAULT);	show_stack(NULL, NULL);} /** * dump_stack - dump the current task information and its stack trace * * Architectures can override this implementation by implementing its own. */#ifdef CONFIG_SMPstatic 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);}#elseasmlinkage __visible void dump_stack(void){	__dump_stack();}#endifEXPORT_SYMBOL(dump_stack);