Merge tag 'hyperv-fixes-signed-20211007' of git://git.kernel.org/pub/scm/linux/kernel...
[platform/kernel/linux-rpi.git] / lib / nmi_backtrace.c
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         clear_bit_unlock(0, &backtrace_flag);
79         put_cpu();
80 }
81
82 // Dump stacks even for idle CPUs.
83 static bool backtrace_idle;
84 module_param(backtrace_idle, bool, 0644);
85
86 bool nmi_cpu_backtrace(struct pt_regs *regs)
87 {
88         int cpu = smp_processor_id();
89         unsigned long flags;
90
91         if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
92                 /*
93                  * Allow nested NMI backtraces while serializing
94                  * against other CPUs.
95                  */
96                 printk_cpu_lock_irqsave(flags);
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                 printk_cpu_unlock_irqrestore(flags);
108                 cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
109                 return true;
110         }
111
112         return false;
113 }
114 NOKPROBE_SYMBOL(nmi_cpu_backtrace);
115 #endif