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Commit	Line	Data
	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* NMI backtrace support
	4	*
	5	* Gratuitously copied from arch/x86/kernel/apic/hw_nmi.c by Russell King,
	6	* with the following header:
	7	*
	8	* HW NMI watchdog support
	9	*
	10	* started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
	11	*
	12	* Arch specific calls to support NMI watchdog
	13	*
	14	* Bits copied from original nmi.c file
	15	*/
	16	#include <linux/cpumask.h>
	17	#include <linux/delay.h>
	18	#include <linux/kprobes.h>
	19	#include <linux/nmi.h>
	20	#include <linux/cpu.h>
	21	#include <linux/sched/debug.h>
	22
	23	#ifdef arch_trigger_cpumask_backtrace
	24	/* For reliability, we're prepared to waste bits here. */
	25	static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
	26
	27	/* "in progress" flag of arch_trigger_cpumask_backtrace */
	28	static unsigned long backtrace_flag;
	29
	30	/*
	31	* When raise() is called it will be passed a pointer to the
	32	* backtrace_mask. Architectures that call nmi_cpu_backtrace()
	33	* directly from their raise() functions may rely on the mask
	34	* they are passed being updated as a side effect of this call.
	35	*/
	36	void nmi_trigger_cpumask_backtrace(const cpumask_t *mask,
	37	bool exclude_self,
	38	void (raise)(cpumask_t mask))
	39	{
	40	int i, this_cpu = get_cpu();
	41
	42	if (test_and_set_bit(0, &backtrace_flag)) {
	43	/*
	44	* If there is already a trigger_all_cpu_backtrace() in progress
	45	* (backtrace_flag == 1), don't output double cpu dump infos.
	46	*/
	47	put_cpu();
	48	return;
	49	}
	50
	51	cpumask_copy(to_cpumask(backtrace_mask), mask);
	52	if (exclude_self)
	53	cpumask_clear_cpu(this_cpu, to_cpumask(backtrace_mask));
	54
	55	/*
	56	* Don't try to send an NMI to this cpu; it may work on some
	57	* architectures, but on others it may not, and we'll get
	58	* information at least as useful just by doing a dump_stack() here.
	59	* Note that nmi_cpu_backtrace(NULL) will clear the cpu bit.
	60	*/
	61	if (cpumask_test_cpu(this_cpu, to_cpumask(backtrace_mask)))
	62	nmi_cpu_backtrace(NULL);
	63
	64	if (!cpumask_empty(to_cpumask(backtrace_mask))) {
	65	pr_info("Sending NMI from CPU %d to CPUs %*pbl:\n",
	66	this_cpu, nr_cpumask_bits, to_cpumask(backtrace_mask));
	67	raise(to_cpumask(backtrace_mask));
	68	}
	69
	70	/* Wait for up to 10 seconds for all CPUs to do the backtrace */
	71	for (i = 0; i < 10 * 1000; i++) {
	72	if (cpumask_empty(to_cpumask(backtrace_mask)))
	73	break;
	74	mdelay(1);
	75	touch_softlockup_watchdog();
	76	}
	77
	78	/*
	79	* Force flush any remote buffers that might be stuck in IRQ context
	80	* and therefore could not run their irq_work.
	81	*/
	82	printk_safe_flush();
	83
	84	clear_bit_unlock(0, &backtrace_flag);
	85	put_cpu();
	86	}
	87
	88	// Dump stacks even for idle CPUs.
	89	static bool backtrace_idle;
	90	module_param(backtrace_idle, bool, 0644);
	91
	92	bool nmi_cpu_backtrace(struct pt_regs *regs)
	93	{
	94	int cpu = smp_processor_id();
	95
	96	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
	97	if (!READ_ONCE(backtrace_idle) && regs && cpu_in_idle(instruction_pointer(regs))) {
	98	pr_warn("NMI backtrace for cpu %d skipped: idling at %pS\n",
	99	cpu, (void *)instruction_pointer(regs));
	100	} else {
	101	pr_warn("NMI backtrace for cpu %d\n", cpu);
	102	if (regs)
	103	show_regs(regs);
	104	else
	105	dump_stack();
	106	}
	107	cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
	108	return true;
	109	}
	110
	111	return false;
	112	}
	113	NOKPROBE_SYMBOL(nmi_cpu_backtrace);
	114	#endif