1 // SPDX-License-Identifier: GPL-2.0-only
2 /* Pseudo NMI support on sparc64 systems.
3 *
4 * Copyright (C) 2009 David S. Miller <davem@davemloft.net>
5 *
6 * The NMI watchdog support and infrastructure is based almost
7 * entirely upon the x86 NMI support code.
8 */
9 #include <linux/kernel.h>
10 #include <linux/param.h>
11 #include <linux/init.h>
12 #include <linux/percpu.h>
13 #include <linux/nmi.h>
14 #include <linux/export.h>
15 #include <linux/kprobes.h>
16 #include <linux/kernel_stat.h>
17 #include <linux/reboot.h>
18 #include <linux/slab.h>
19 #include <linux/kdebug.h>
20 #include <linux/delay.h>
21 #include <linux/smp.h>
22
23 #include <asm/perf_event.h>
24 #include <asm/ptrace.h>
25 #include <asm/pcr.h>
26
27 #include "kstack.h"
28
29 /* We don't have a real NMI on sparc64, but we can fake one
30 * up using profiling counter overflow interrupts and interrupt
31 * levels.
32 *
33 * The profile overflow interrupts at level 15, so we use
34 * level 14 as our IRQ off level.
35 */
36
37 static int panic_on_timeout;
38
39 /* nmi_active:
40 * >0: the NMI watchdog is active, but can be disabled
41 * <0: the NMI watchdog has not been set up, and cannot be enabled
42 * 0: the NMI watchdog is disabled, but can be enabled
43 */
44 atomic_t nmi_active = ATOMIC_INIT(0); /* oprofile uses this */
45 EXPORT_SYMBOL(nmi_active);
46 static int nmi_init_done;
47 static unsigned int nmi_hz = HZ;
48 static DEFINE_PER_CPU(short, wd_enabled);
49 static int endflag __initdata;
50
51 static DEFINE_PER_CPU(unsigned int, last_irq_sum);
52 static DEFINE_PER_CPU(long, alert_counter);
53 static DEFINE_PER_CPU(int, nmi_touch);
54
55 void arch_touch_nmi_watchdog(void)
56 {
57 if (atomic_read(&nmi_active)) {
58 int cpu;
59
60 for_each_present_cpu(cpu) {
61 if (per_cpu(nmi_touch, cpu) != 1)
62 per_cpu(nmi_touch, cpu) = 1;
63 }
64 }
65 }
66 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
67
68 int __init watchdog_hardlockup_probe(void)
69 {
70 return 0;
71 }
72
73 static void die_nmi(const char *str, struct pt_regs *regs, int do_panic)
74 {
75 int this_cpu = smp_processor_id();
76
77 if (notify_die(DIE_NMIWATCHDOG, str, regs, 0,
78 pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
79 return;
80
81 if (do_panic || panic_on_oops)
82 panic("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
83 else
84 WARN(1, "Watchdog detected hard LOCKUP on cpu %d", this_cpu);
85 }
86
87 notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
88 {
89 unsigned int sum, touched = 0;
90 void *orig_sp;
91
92 clear_softint(1 << irq);
93
94 local_cpu_data().__nmi_count++;
95
96 nmi_enter();
97
98 orig_sp = set_hardirq_stack();
99
100 if (notify_die(DIE_NMI, "nmi", regs, 0,
101 pt_regs_trap_type(regs), SIGINT) == NOTIFY_STOP)
102 touched = 1;
103 else
104 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
105
106 sum = local_cpu_data().irq0_irqs;
107 if (__this_cpu_read(nmi_touch)) {
108 __this_cpu_write(nmi_touch, 0);
109 touched = 1;
110 }
111 if (!touched && __this_cpu_read(last_irq_sum) == sum) {
112 __this_cpu_inc(alert_counter);
113 if (__this_cpu_read(alert_counter) == 30 * nmi_hz)
114 die_nmi("BUG: NMI Watchdog detected LOCKUP",
115 regs, panic_on_timeout);
116 } else {
117 __this_cpu_write(last_irq_sum, sum);
118 __this_cpu_write(alert_counter, 0);
119 }
120 if (__this_cpu_read(wd_enabled)) {
121 pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
122 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
123 }
124
125 restore_hardirq_stack(orig_sp);
126
127 nmi_exit();
128 }
129
130 static inline unsigned int get_nmi_count(int cpu)
131 {
132 return cpu_data(cpu).__nmi_count;
133 }
134
135 static __init void nmi_cpu_busy(void *data)
136 {
137 while (endflag == 0)
138 mb();
139 }
140
141 static void report_broken_nmi(int cpu, int *prev_nmi_count)
142 {
143 printk(KERN_CONT "\n");
144
145 printk(KERN_WARNING
146 "WARNING: CPU#%d: NMI appears to be stuck (%d->%d)!\n",
147 cpu, prev_nmi_count[cpu], get_nmi_count(cpu));
148
149 printk(KERN_WARNING
150 "Please report this to bugzilla.kernel.org,\n");
151 printk(KERN_WARNING
152 "and attach the output of the 'dmesg' command.\n");
153
154 per_cpu(wd_enabled, cpu) = 0;
155 atomic_dec(&nmi_active);
156 }
157
158 void stop_nmi_watchdog(void *unused)
159 {
160 if (!__this_cpu_read(wd_enabled))
161 return;
162 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
163 __this_cpu_write(wd_enabled, 0);
164 atomic_dec(&nmi_active);
165 }
166
167 static int __init check_nmi_watchdog(void)
168 {
169 unsigned int *prev_nmi_count;
170 int cpu, err;
171
172 if (!atomic_read(&nmi_active))
173 return 0;
174
175 prev_nmi_count = kmalloc_array(nr_cpu_ids, sizeof(unsigned int),
176 GFP_KERNEL);
177 if (!prev_nmi_count) {
178 err = -ENOMEM;
179 goto error;
180 }
181
182 printk(KERN_INFO "Testing NMI watchdog ... ");
183
184 smp_call_function(nmi_cpu_busy, (void *)&endflag, 0);
185
186 for_each_possible_cpu(cpu)
187 prev_nmi_count[cpu] = get_nmi_count(cpu);
188 local_irq_enable();
189 mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
190
191 for_each_online_cpu(cpu) {
192 if (!per_cpu(wd_enabled, cpu))
193 continue;
194 if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
195 report_broken_nmi(cpu, prev_nmi_count);
196 }
197 endflag = 1;
198 if (!atomic_read(&nmi_active)) {
199 kfree(prev_nmi_count);
200 atomic_set(&nmi_active, -1);
201 err = -ENODEV;
202 goto error;
203 }
204 printk("OK.\n");
205
206 nmi_hz = 1;
207
208 kfree(prev_nmi_count);
209 return 0;
210 error:
211 on_each_cpu(stop_nmi_watchdog, NULL, 1);
212 return err;
213 }
214
215 void start_nmi_watchdog(void *unused)
216 {
217 if (__this_cpu_read(wd_enabled))
218 return;
219
220 __this_cpu_write(wd_enabled, 1);
221 atomic_inc(&nmi_active);
222
223 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
224 pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
225
226 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
227 }
228
229 static void nmi_adjust_hz_one(void *unused)
230 {
231 if (!__this_cpu_read(wd_enabled))
232 return;
233
234 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_disable);
235 pcr_ops->write_pic(0, pcr_ops->nmi_picl_value(nmi_hz));
236
237 pcr_ops->write_pcr(0, pcr_ops->pcr_nmi_enable);
238 }
239
240 void nmi_adjust_hz(unsigned int new_hz)
241 {
242 nmi_hz = new_hz;
243 on_each_cpu(nmi_adjust_hz_one, NULL, 1);
244 }
245 EXPORT_SYMBOL_GPL(nmi_adjust_hz);
246
247 static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
248 {
249 on_each_cpu(stop_nmi_watchdog, NULL, 1);
250 return 0;
251 }
252
253 static struct notifier_block nmi_reboot_notifier = {
254 .notifier_call = nmi_shutdown,
255 };
256
257 int __init nmi_init(void)
258 {
259 int err;
260
261 on_each_cpu(start_nmi_watchdog, NULL, 1);
262
263 err = check_nmi_watchdog();
264 if (!err) {
265 err = register_reboot_notifier(&nmi_reboot_notifier);
266 if (err) {
267 on_each_cpu(stop_nmi_watchdog, NULL, 1);
268 atomic_set(&nmi_active, -1);
269 }
270 }
271
272 nmi_init_done = 1;
273
274 return err;
275 }
276
277 static int __init setup_nmi_watchdog(char *str)
278 {
279 if (!strncmp(str, "panic", 5))
280 panic_on_timeout = 1;
281
282 return 1;
283 }
284 __setup("nmi_watchdog=", setup_nmi_watchdog);
285
286 /*
287 * sparc specific NMI watchdog enable function.
288 * Enables watchdog if it is not enabled already.
289 */
290 void watchdog_hardlockup_enable(unsigned int cpu)
291 {
292 if (atomic_read(&nmi_active) == -1) {
293 pr_warn("NMI watchdog cannot be enabled or disabled\n");
294 return;
295 }
296
297 /*
298 * watchdog thread could start even before nmi_init is called.
299 * Just Return in that case. Let nmi_init finish the init
300 * process first.
301 */
302 if (!nmi_init_done)
303 return;
304
305 smp_call_function_single(cpu, start_nmi_watchdog, NULL, 1);
306 }
307 /*
308 * sparc specific NMI watchdog disable function.
309 * Disables watchdog if it is not disabled already.
310 */
311 void watchdog_hardlockup_disable(unsigned int cpu)
312 {
313 if (atomic_read(&nmi_active) == -1)
314 pr_warn_once("NMI watchdog cannot be enabled or disabled\n");
315 else
316 smp_call_function_single(cpu, stop_nmi_watchdog, NULL, 1);
317 }
318
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