// SPDX-License-Identifier: GPL-2.0/* *  NMI backtrace support * * Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King, * with the following header: * *  HW NMI watchdog support * *  started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. * *  Arch specific calls to support NMI watchdog * *  Bits copied from original nmi.c file */#include <linux/cpumask.h>#include <linux/delay.h>#include <linux/kprobes.h>#include <linux/stringify.h>#include <linux/nmi.h>#include <linux/cpu.h>#include <linux/export.h>#include <linux/sched/debug.h> #ifdef arch_trigger_cpumask_backtrace/* For reliability, we're prepared to waste bits here. */static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly; /* "in progress" flag of arch_trigger_cpumask_backtrace */static unsigned long backtrace_flag; #define NMI_BT_TIMEOUT_SEC	10 /* * When raise() is called it will be passed a pointer to the * backtrace_mask. Architectures that call nmi_cpu_backtrace() * directly from their raise() functions may rely on the mask * they are passed being updated as a side effect of this call. */void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,				   int exclude_cpu,				   void (*raise)(cpumask_t *mask)){	int i, this_cpu = get_cpu(); 	if (test_and_set_bit(0, &backtrace_flag)) {		/*		 * If there is already a trigger_all_cpu_backtrace() in progress		 * (backtrace_flag == 1), don't output double cpu dump infos.		 */		put_cpu();		return;	} 	cpumask_copy(to_cpumask(backtrace_mask), mask);	if (exclude_cpu != -1)		cpumask_clear_cpu(exclude_cpu, to_cpumask(backtrace_mask)); 	/*	 * Don't try to send an NMI to this cpu; it may work on some	 * architectures, but on others it may not, and we'll get	 * information at least as useful just by doing a dump_stack() here.	 * Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.	 */	if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))		nmi_cpu_backtrace(NULL); 	if (!cpumask_empty(to_cpumask(backtrace_mask))) {		pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",			this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));		nmi_backtrace_stall_snap(to_cpumask(backtrace_mask));		raise(to_cpumask(backtrace_mask));	} 	/* Wait for up to NMI_BT_TIMEOUT_SEC seconds for all CPUs to do the backtrace */	for (i = 0; i < NMI_BT_TIMEOUT_SEC * 1000; i++) {		if (cpumask_empty(to_cpumask(backtrace_mask)))			break;		mdelay(1);		touch_softlockup_watchdog();	} 	if (!cpumask_empty(to_cpumask(backtrace_mask))) {		pr_warn("After " __stringify(NMI_BT_TIMEOUT_SEC) " seconds, these CPUS still haven't responded to the NMI: %*pbl\n",			cpumask_pr_args(to_cpumask(backtrace_mask))); 		nmi_backtrace_stall_check(to_cpumask(backtrace_mask));	} 	/*	 * Force flush any remote buffers that might be stuck in IRQ context	 * and therefore could not run their irq_work.	 */	printk_trigger_flush(); 	clear_bit_unlock(0, &backtrace_flag);	put_cpu();} // Dump stacks even for idle CPUs.static bool backtrace_idle;module_param(backtrace_idle, bool, 0644); bool nmi_cpu_backtrace(struct pt_regs *regs){	int cpu = smp_processor_id();	unsigned long flags; 	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {		/*		 * Allow nested NMI backtraces while serializing		 * against other CPUs.		 */		printk_cpu_sync_get_irqsave(flags);		if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {			pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",				cpu, (void *)instruction_pointer(regs));		} else {			pr_warn("NMI backtrace for cpu %d\n", cpu);			if (regs)				show_regs(regs);			else				dump_stack();		}		printk_cpu_sync_put_irqrestore(flags);		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));		return true;	} 	return false;}NOKPROBE_SYMBOL(nmi_cpu_backtrace); void cpumask_backtrace(const cpumask_t *mask, int exclude_cpu){	arch_trigger_cpumask_backtrace(mask, exclude_cpu);}EXPORT_SYMBOL_GPL(cpumask_backtrace);#endif