1 // SPDX-License-Identifier: GPL-2.0 1
2 /*
3 * Detect hard lockups on a system using perf
4 *
5 * started by Don Zickus, Copyright (C) 2010 R
6 *
7 * Note: Most of this code is borrowed heavily
8 * detector, so thanks to Ingo for the initial
9 * Some chunks also taken from the old x86-spe
10 * to those contributors as well.
11 */
12
13 #define pr_fmt(fmt) "NMI watchdog: " fmt
14
15 #include <linux/nmi.h>
16 #include <linux/atomic.h>
17 #include <linux/module.h>
18 #include <linux/sched/debug.h>
19
20 #include <asm/irq_regs.h>
21 #include <linux/perf_event.h>
22
23 static DEFINE_PER_CPU(struct perf_event *, wat
24 static DEFINE_PER_CPU(struct perf_event *, dea
25 static struct cpumask dead_events_mask;
26
27 static atomic_t watchdog_cpus = ATOMIC_INIT(0)
28
29 #ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMP
30 static DEFINE_PER_CPU(ktime_t, last_timestamp)
31 static DEFINE_PER_CPU(unsigned int, nmi_rearme
32 static ktime_t watchdog_hrtimer_sample_thresho
33
34 void watchdog_update_hrtimer_threshold(u64 per
35 {
36 /*
37 * The hrtimer runs with a period of (
38 *
39 * So it runs effectively with 2.5 tim
40 * watchdog. That means the hrtimer sh
41 * the NMI watchdog expires. The NMI w
42 * unhalted CPU cycles, so if Turbo-Mo
43 * might run way faster than expected
44 * smaller period than the one deduced
45 * frequency. Depending on the Turbo-M
46 * enough to get the NMI period smalle
47 * period and trigger false positives.
48 *
49 * The sample threshold is used to che
50 * the minimum time between two NMI sa
51 * prevents false positives.
52 *
53 * Set this to 4/5 of the actual watch
54 * hrtimer is guaranteed to fire at le
55 * watchdog threshold.
56 */
57 watchdog_hrtimer_sample_threshold = pe
58 }
59
60 static bool watchdog_check_timestamp(void)
61 {
62 ktime_t delta, now = ktime_get_mono_fa
63
64 delta = now - __this_cpu_read(last_tim
65 if (delta < watchdog_hrtimer_sample_th
66 /*
67 * If ktime is jiffies based,
68 * jiffies from being incremen
69 * at a stale timestamp and ne
70 */
71 if (__this_cpu_inc_return(nmi_
72 return false;
73 }
74 __this_cpu_write(nmi_rearmed, 0);
75 __this_cpu_write(last_timestamp, now);
76 return true;
77 }
78
79 static void watchdog_init_timestamp(void)
80 {
81 __this_cpu_write(nmi_rearmed, 0);
82 __this_cpu_write(last_timestamp, ktime
83 }
84 #else
85 static inline bool watchdog_check_timestamp(vo
86 static inline void watchdog_init_timestamp(voi
87 #endif
88
89 static struct perf_event_attr wd_hw_attr = {
90 .type = PERF_TYPE_HARDWARE,
91 .config = PERF_COUNT_HW_CPU_CY
92 .size = sizeof(struct perf_e
93 .pinned = 1,
94 .disabled = 1,
95 };
96
97 static struct perf_event_attr fallback_wd_hw_a
98 .type = PERF_TYPE_HARDWARE,
99 .config = PERF_COUNT_HW_CPU_CY
100 .size = sizeof(struct perf_e
101 .pinned = 1,
102 .disabled = 1,
103 };
104
105 /* Callback function for perf event subsystem
106 static void watchdog_overflow_callback(struct
107 struct
108 struct
109 {
110 /* Ensure the watchdog never gets thro
111 event->hw.interrupts = 0;
112
113 if (!watchdog_check_timestamp())
114 return;
115
116 watchdog_hardlockup_check(smp_processo
117 }
118
119 static int hardlockup_detector_event_create(vo
120 {
121 unsigned int cpu;
122 struct perf_event_attr *wd_attr;
123 struct perf_event *evt;
124
125 /*
126 * Preemption is not disabled because
127 * Ensure CPU-locality by calling this
128 */
129 WARN_ON(!is_percpu_thread());
130 cpu = raw_smp_processor_id();
131 wd_attr = &wd_hw_attr;
132 wd_attr->sample_period = hw_nmi_get_sa
133
134 /* Try to register using hardware perf
135 evt = perf_event_create_kernel_counter
136
137 if (IS_ERR(evt)) {
138 wd_attr = &fallback_wd_hw_attr
139 wd_attr->sample_period = hw_nm
140 evt = perf_event_create_kernel
141
142 }
143
144 if (IS_ERR(evt)) {
145 pr_debug("Perf event create on
146 PTR_ERR(evt));
147 return PTR_ERR(evt);
148 }
149 this_cpu_write(watchdog_ev, evt);
150 return 0;
151 }
152
153 /**
154 * watchdog_hardlockup_enable - Enable the loc
155 * @cpu: The CPU to enable hard lockup on.
156 */
157 void watchdog_hardlockup_enable(unsigned int c
158 {
159 WARN_ON_ONCE(cpu != smp_processor_id()
160
161 if (hardlockup_detector_event_create()
162 return;
163
164 /* use original value for check */
165 if (!atomic_fetch_inc(&watchdog_cpus))
166 pr_info("Enabled. Permanently
167
168 watchdog_init_timestamp();
169 perf_event_enable(this_cpu_read(watchd
170 }
171
172 /**
173 * watchdog_hardlockup_disable - Disable the l
174 * @cpu: The CPU to enable hard lockup on.
175 */
176 void watchdog_hardlockup_disable(unsigned int
177 {
178 struct perf_event *event = this_cpu_re
179
180 WARN_ON_ONCE(cpu != smp_processor_id()
181
182 if (event) {
183 perf_event_disable(event);
184 this_cpu_write(watchdog_ev, NU
185 this_cpu_write(dead_event, eve
186 cpumask_set_cpu(smp_processor_
187 atomic_dec(&watchdog_cpus);
188 }
189 }
190
191 /**
192 * hardlockup_detector_perf_cleanup - Cleanup
193 *
194 * Called from lockup_detector_cleanup(). Seri
195 */
196 void hardlockup_detector_perf_cleanup(void)
197 {
198 int cpu;
199
200 for_each_cpu(cpu, &dead_events_mask) {
201 struct perf_event *event = per
202
203 /*
204 * Required because for_each_c
205 * CPU0 as set on UP kernels.
206 */
207 if (event)
208 perf_event_release_ker
209 per_cpu(dead_event, cpu) = NUL
210 }
211 cpumask_clear(&dead_events_mask);
212 }
213
214 /**
215 * hardlockup_detector_perf_stop - Globally st
216 *
217 * Special interface for x86 to handle the per
218 */
219 void __init hardlockup_detector_perf_stop(void
220 {
221 int cpu;
222
223 lockdep_assert_cpus_held();
224
225 for_each_online_cpu(cpu) {
226 struct perf_event *event = per
227
228 if (event)
229 perf_event_disable(eve
230 }
231 }
232
233 /**
234 * hardlockup_detector_perf_restart - Globally
235 *
236 * Special interface for x86 to handle the per
237 */
238 void __init hardlockup_detector_perf_restart(v
239 {
240 int cpu;
241
242 lockdep_assert_cpus_held();
243
244 if (!(watchdog_enabled & WATCHDOG_HARD
245 return;
246
247 for_each_online_cpu(cpu) {
248 struct perf_event *event = per
249
250 if (event)
251 perf_event_enable(even
252 }
253 }
254
255 bool __weak __init arch_perf_nmi_is_available(
256 {
257 return true;
258 }
259
260 /**
261 * watchdog_hardlockup_probe - Probe whether N
262 */
263 int __init watchdog_hardlockup_probe(void)
264 {
265 int ret;
266
267 if (!arch_perf_nmi_is_available())
268 return -ENODEV;
269
270 ret = hardlockup_detector_event_create
271
272 if (ret) {
273 pr_info("Perf NMI watchdog per
274 } else {
275 perf_event_release_kernel(this
276 this_cpu_write(watchdog_ev, NU
277 }
278 return ret;
279 }
280
281 /**
282 * hardlockup_config_perf_event - Overwrite co
283 * @str: number which identifies the raw perf
284 */
285 void __init hardlockup_config_perf_event(const
286 {
287 u64 config;
288 char buf[24];
289 char *comma = strchr(str, ',');
290
291 if (!comma) {
292 if (kstrtoull(str, 16, &config
293 return;
294 } else {
295 unsigned int len = comma - str
296
297 if (len >= sizeof(buf))
298 return;
299
300 if (strscpy(buf, str, sizeof(b
301 return;
302 buf[len] = 0;
303 if (kstrtoull(buf, 16, &config
304 return;
305 }
306
307 wd_hw_attr.type = PERF_TYPE_RAW;
308 wd_hw_attr.config = config;
309 }
310
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