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