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 #else
79 static void watchdog_init_timestamp(void) !! 79 static inline bool watchdog_check_timestamp(void)
80 { 80 {
81 __this_cpu_write(nmi_rearmed, 0); !! 81 return true;
82 __this_cpu_write(last_timestamp, ktime <<
83 } 82 }
84 #else <<
85 static inline bool watchdog_check_timestamp(vo <<
86 static inline void watchdog_init_timestamp(voi <<
87 #endif 83 #endif
88 84
89 static struct perf_event_attr wd_hw_attr = { 85 static struct perf_event_attr wd_hw_attr = {
90 .type = PERF_TYPE_HARDWARE, 86 .type = PERF_TYPE_HARDWARE,
91 .config = PERF_COUNT_HW_CPU_CY 87 .config = PERF_COUNT_HW_CPU_CYCLES,
92 .size = sizeof(struct perf_e 88 .size = sizeof(struct perf_event_attr),
93 .pinned = 1, 89 .pinned = 1,
94 .disabled = 1, 90 .disabled = 1,
95 }; 91 };
96 92
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 93 /* Callback function for perf event subsystem */
106 static void watchdog_overflow_callback(struct 94 static void watchdog_overflow_callback(struct perf_event *event,
107 struct 95 struct perf_sample_data *data,
108 struct 96 struct pt_regs *regs)
109 { 97 {
110 /* Ensure the watchdog never gets thro 98 /* Ensure the watchdog never gets throttled */
111 event->hw.interrupts = 0; 99 event->hw.interrupts = 0;
112 100
113 if (!watchdog_check_timestamp()) 101 if (!watchdog_check_timestamp())
114 return; 102 return;
115 103
116 watchdog_hardlockup_check(smp_processo 104 watchdog_hardlockup_check(smp_processor_id(), regs);
117 } 105 }
118 106
119 static int hardlockup_detector_event_create(vo 107 static int hardlockup_detector_event_create(void)
120 { 108 {
121 unsigned int cpu; 109 unsigned int cpu;
122 struct perf_event_attr *wd_attr; 110 struct perf_event_attr *wd_attr;
123 struct perf_event *evt; 111 struct perf_event *evt;
124 112
125 /* 113 /*
126 * Preemption is not disabled because 114 * Preemption is not disabled because memory will be allocated.
127 * Ensure CPU-locality by calling this 115 * Ensure CPU-locality by calling this in per-CPU kthread.
128 */ 116 */
129 WARN_ON(!is_percpu_thread()); 117 WARN_ON(!is_percpu_thread());
130 cpu = raw_smp_processor_id(); 118 cpu = raw_smp_processor_id();
131 wd_attr = &wd_hw_attr; 119 wd_attr = &wd_hw_attr;
132 wd_attr->sample_period = hw_nmi_get_sa 120 wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
133 121
134 /* Try to register using hardware perf 122 /* Try to register using hardware perf events */
135 evt = perf_event_create_kernel_counter 123 evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
136 124 watchdog_overflow_callback, NULL);
137 if (IS_ERR(evt)) { 125 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 126 pr_debug("Perf event create on CPU %d failed with %ld\n", cpu,
146 PTR_ERR(evt)); 127 PTR_ERR(evt));
147 return PTR_ERR(evt); 128 return PTR_ERR(evt);
148 } 129 }
149 this_cpu_write(watchdog_ev, evt); 130 this_cpu_write(watchdog_ev, evt);
150 return 0; 131 return 0;
151 } 132 }
152 133
153 /** 134 /**
154 * watchdog_hardlockup_enable - Enable the loc 135 * watchdog_hardlockup_enable - Enable the local event
>> 136 *
155 * @cpu: The CPU to enable hard lockup on. 137 * @cpu: The CPU to enable hard lockup on.
156 */ 138 */
157 void watchdog_hardlockup_enable(unsigned int c 139 void watchdog_hardlockup_enable(unsigned int cpu)
158 { 140 {
159 WARN_ON_ONCE(cpu != smp_processor_id() 141 WARN_ON_ONCE(cpu != smp_processor_id());
160 142
161 if (hardlockup_detector_event_create() 143 if (hardlockup_detector_event_create())
162 return; 144 return;
163 145
164 /* use original value for check */ 146 /* use original value for check */
165 if (!atomic_fetch_inc(&watchdog_cpus)) 147 if (!atomic_fetch_inc(&watchdog_cpus))
166 pr_info("Enabled. Permanently 148 pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
167 149
168 watchdog_init_timestamp(); <<
169 perf_event_enable(this_cpu_read(watchd 150 perf_event_enable(this_cpu_read(watchdog_ev));
170 } 151 }
171 152
172 /** 153 /**
173 * watchdog_hardlockup_disable - Disable the l 154 * watchdog_hardlockup_disable - Disable the local event
>> 155 *
174 * @cpu: The CPU to enable hard lockup on. 156 * @cpu: The CPU to enable hard lockup on.
175 */ 157 */
176 void watchdog_hardlockup_disable(unsigned int 158 void watchdog_hardlockup_disable(unsigned int cpu)
177 { 159 {
178 struct perf_event *event = this_cpu_re 160 struct perf_event *event = this_cpu_read(watchdog_ev);
179 161
180 WARN_ON_ONCE(cpu != smp_processor_id() 162 WARN_ON_ONCE(cpu != smp_processor_id());
181 163
182 if (event) { 164 if (event) {
183 perf_event_disable(event); 165 perf_event_disable(event);
184 this_cpu_write(watchdog_ev, NU 166 this_cpu_write(watchdog_ev, NULL);
185 this_cpu_write(dead_event, eve 167 this_cpu_write(dead_event, event);
186 cpumask_set_cpu(smp_processor_ 168 cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
187 atomic_dec(&watchdog_cpus); 169 atomic_dec(&watchdog_cpus);
188 } 170 }
189 } 171 }
190 172
191 /** 173 /**
192 * hardlockup_detector_perf_cleanup - Cleanup 174 * hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them
193 * 175 *
194 * Called from lockup_detector_cleanup(). Seri 176 * Called from lockup_detector_cleanup(). Serialized by the caller.
195 */ 177 */
196 void hardlockup_detector_perf_cleanup(void) 178 void hardlockup_detector_perf_cleanup(void)
197 { 179 {
198 int cpu; 180 int cpu;
199 181
200 for_each_cpu(cpu, &dead_events_mask) { 182 for_each_cpu(cpu, &dead_events_mask) {
201 struct perf_event *event = per 183 struct perf_event *event = per_cpu(dead_event, cpu);
202 184
203 /* 185 /*
204 * Required because for_each_c 186 * Required because for_each_cpu() reports unconditionally
205 * CPU0 as set on UP kernels. 187 * CPU0 as set on UP kernels. Sigh.
206 */ 188 */
207 if (event) 189 if (event)
208 perf_event_release_ker 190 perf_event_release_kernel(event);
209 per_cpu(dead_event, cpu) = NUL 191 per_cpu(dead_event, cpu) = NULL;
210 } 192 }
211 cpumask_clear(&dead_events_mask); 193 cpumask_clear(&dead_events_mask);
212 } 194 }
213 195
214 /** 196 /**
215 * hardlockup_detector_perf_stop - Globally st 197 * hardlockup_detector_perf_stop - Globally stop watchdog events
216 * 198 *
217 * Special interface for x86 to handle the per 199 * Special interface for x86 to handle the perf HT bug.
218 */ 200 */
219 void __init hardlockup_detector_perf_stop(void 201 void __init hardlockup_detector_perf_stop(void)
220 { 202 {
221 int cpu; 203 int cpu;
222 204
223 lockdep_assert_cpus_held(); 205 lockdep_assert_cpus_held();
224 206
225 for_each_online_cpu(cpu) { 207 for_each_online_cpu(cpu) {
226 struct perf_event *event = per 208 struct perf_event *event = per_cpu(watchdog_ev, cpu);
227 209
228 if (event) 210 if (event)
229 perf_event_disable(eve 211 perf_event_disable(event);
230 } 212 }
231 } 213 }
232 214
233 /** 215 /**
234 * hardlockup_detector_perf_restart - Globally 216 * hardlockup_detector_perf_restart - Globally restart watchdog events
235 * 217 *
236 * Special interface for x86 to handle the per 218 * Special interface for x86 to handle the perf HT bug.
237 */ 219 */
238 void __init hardlockup_detector_perf_restart(v 220 void __init hardlockup_detector_perf_restart(void)
239 { 221 {
240 int cpu; 222 int cpu;
241 223
242 lockdep_assert_cpus_held(); 224 lockdep_assert_cpus_held();
243 225
244 if (!(watchdog_enabled & WATCHDOG_HARD 226 if (!(watchdog_enabled & WATCHDOG_HARDLOCKUP_ENABLED))
245 return; 227 return;
246 228
247 for_each_online_cpu(cpu) { 229 for_each_online_cpu(cpu) {
248 struct perf_event *event = per 230 struct perf_event *event = per_cpu(watchdog_ev, cpu);
249 231
250 if (event) 232 if (event)
251 perf_event_enable(even 233 perf_event_enable(event);
252 } 234 }
253 } 235 }
254 236
255 bool __weak __init arch_perf_nmi_is_available( 237 bool __weak __init arch_perf_nmi_is_available(void)
256 { 238 {
257 return true; 239 return true;
258 } 240 }
259 241
260 /** 242 /**
261 * watchdog_hardlockup_probe - Probe whether N 243 * watchdog_hardlockup_probe - Probe whether NMI event is available at all
262 */ 244 */
263 int __init watchdog_hardlockup_probe(void) 245 int __init watchdog_hardlockup_probe(void)
264 { 246 {
265 int ret; 247 int ret;
266 248
267 if (!arch_perf_nmi_is_available()) 249 if (!arch_perf_nmi_is_available())
268 return -ENODEV; 250 return -ENODEV;
269 251
270 ret = hardlockup_detector_event_create 252 ret = hardlockup_detector_event_create();
271 253
272 if (ret) { 254 if (ret) {
273 pr_info("Perf NMI watchdog per 255 pr_info("Perf NMI watchdog permanently disabled\n");
274 } else { 256 } else {
275 perf_event_release_kernel(this 257 perf_event_release_kernel(this_cpu_read(watchdog_ev));
276 this_cpu_write(watchdog_ev, NU 258 this_cpu_write(watchdog_ev, NULL);
277 } 259 }
278 return ret; 260 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 } 261 }
310 262
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