Commit | Line | Data |
---|---|---|
73ce0511 BM |
1 | /* |
2 | * Detect hard lockups on a system | |
3 | * | |
4 | * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc. | |
5 | * | |
6 | * Note: Most of this code is borrowed heavily from the original softlockup | |
7 | * detector, so thanks to Ingo for the initial implementation. | |
8 | * Some chunks also taken from the old x86-specific nmi watchdog code, thanks | |
9 | * to those contributors as well. | |
10 | */ | |
11 | ||
12 | #define pr_fmt(fmt) "NMI watchdog: " fmt | |
13 | ||
14 | #include <linux/nmi.h> | |
15 | #include <linux/module.h> | |
b17b0153 IM |
16 | #include <linux/sched/debug.h> |
17 | ||
73ce0511 BM |
18 | #include <asm/irq_regs.h> |
19 | #include <linux/perf_event.h> | |
20 | ||
21 | static DEFINE_PER_CPU(bool, hard_watchdog_warn); | |
22 | static DEFINE_PER_CPU(bool, watchdog_nmi_touch); | |
23 | static DEFINE_PER_CPU(struct perf_event *, watchdog_ev); | |
941154bd | 24 | static struct cpumask dead_events_mask; |
73ce0511 | 25 | |
73ce0511 | 26 | static unsigned long hardlockup_allcpu_dumped; |
146c9d0e | 27 | static unsigned int watchdog_cpus; |
73ce0511 | 28 | |
f2e0cff8 | 29 | void arch_touch_nmi_watchdog(void) |
73ce0511 BM |
30 | { |
31 | /* | |
32 | * Using __raw here because some code paths have | |
33 | * preemption enabled. If preemption is enabled | |
34 | * then interrupts should be enabled too, in which | |
35 | * case we shouldn't have to worry about the watchdog | |
36 | * going off. | |
37 | */ | |
38 | raw_cpu_write(watchdog_nmi_touch, true); | |
73ce0511 | 39 | } |
f2e0cff8 | 40 | EXPORT_SYMBOL(arch_touch_nmi_watchdog); |
73ce0511 | 41 | |
7edaeb68 TG |
42 | #ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMP |
43 | static DEFINE_PER_CPU(ktime_t, last_timestamp); | |
44 | static DEFINE_PER_CPU(unsigned int, nmi_rearmed); | |
45 | static ktime_t watchdog_hrtimer_sample_threshold __read_mostly; | |
46 | ||
47 | void watchdog_update_hrtimer_threshold(u64 period) | |
48 | { | |
49 | /* | |
50 | * The hrtimer runs with a period of (watchdog_threshold * 2) / 5 | |
51 | * | |
52 | * So it runs effectively with 2.5 times the rate of the NMI | |
53 | * watchdog. That means the hrtimer should fire 2-3 times before | |
54 | * the NMI watchdog expires. The NMI watchdog on x86 is based on | |
55 | * unhalted CPU cycles, so if Turbo-Mode is enabled the CPU cycles | |
56 | * might run way faster than expected and the NMI fires in a | |
57 | * smaller period than the one deduced from the nominal CPU | |
58 | * frequency. Depending on the Turbo-Mode factor this might be fast | |
59 | * enough to get the NMI period smaller than the hrtimer watchdog | |
60 | * period and trigger false positives. | |
61 | * | |
62 | * The sample threshold is used to check in the NMI handler whether | |
63 | * the minimum time between two NMI samples has elapsed. That | |
64 | * prevents false positives. | |
65 | * | |
66 | * Set this to 4/5 of the actual watchdog threshold period so the | |
67 | * hrtimer is guaranteed to fire at least once within the real | |
68 | * watchdog threshold. | |
69 | */ | |
70 | watchdog_hrtimer_sample_threshold = period * 2; | |
71 | } | |
72 | ||
73 | static bool watchdog_check_timestamp(void) | |
74 | { | |
75 | ktime_t delta, now = ktime_get_mono_fast_ns(); | |
76 | ||
77 | delta = now - __this_cpu_read(last_timestamp); | |
78 | if (delta < watchdog_hrtimer_sample_threshold) { | |
79 | /* | |
80 | * If ktime is jiffies based, a stalled timer would prevent | |
81 | * jiffies from being incremented and the filter would look | |
82 | * at a stale timestamp and never trigger. | |
83 | */ | |
84 | if (__this_cpu_inc_return(nmi_rearmed) < 10) | |
85 | return false; | |
86 | } | |
87 | __this_cpu_write(nmi_rearmed, 0); | |
88 | __this_cpu_write(last_timestamp, now); | |
89 | return true; | |
90 | } | |
91 | #else | |
92 | static inline bool watchdog_check_timestamp(void) | |
93 | { | |
94 | return true; | |
95 | } | |
96 | #endif | |
97 | ||
73ce0511 BM |
98 | static struct perf_event_attr wd_hw_attr = { |
99 | .type = PERF_TYPE_HARDWARE, | |
100 | .config = PERF_COUNT_HW_CPU_CYCLES, | |
101 | .size = sizeof(struct perf_event_attr), | |
102 | .pinned = 1, | |
103 | .disabled = 1, | |
104 | }; | |
105 | ||
106 | /* Callback function for perf event subsystem */ | |
107 | static void watchdog_overflow_callback(struct perf_event *event, | |
01f0a027 TG |
108 | struct perf_sample_data *data, |
109 | struct pt_regs *regs) | |
73ce0511 BM |
110 | { |
111 | /* Ensure the watchdog never gets throttled */ | |
112 | event->hw.interrupts = 0; | |
113 | ||
114 | if (__this_cpu_read(watchdog_nmi_touch) == true) { | |
115 | __this_cpu_write(watchdog_nmi_touch, false); | |
116 | return; | |
117 | } | |
118 | ||
7edaeb68 TG |
119 | if (!watchdog_check_timestamp()) |
120 | return; | |
121 | ||
73ce0511 BM |
122 | /* check for a hardlockup |
123 | * This is done by making sure our timer interrupt | |
124 | * is incrementing. The timer interrupt should have | |
125 | * fired multiple times before we overflow'd. If it hasn't | |
126 | * then this is a good indication the cpu is stuck | |
127 | */ | |
128 | if (is_hardlockup()) { | |
129 | int this_cpu = smp_processor_id(); | |
130 | ||
131 | /* only print hardlockups once */ | |
132 | if (__this_cpu_read(hard_watchdog_warn) == true) | |
133 | return; | |
134 | ||
135 | pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu); | |
136 | print_modules(); | |
137 | print_irqtrace_events(current); | |
138 | if (regs) | |
139 | show_regs(regs); | |
140 | else | |
141 | dump_stack(); | |
142 | ||
143 | /* | |
144 | * Perform all-CPU dump only once to avoid multiple hardlockups | |
145 | * generating interleaving traces | |
146 | */ | |
147 | if (sysctl_hardlockup_all_cpu_backtrace && | |
148 | !test_and_set_bit(0, &hardlockup_allcpu_dumped)) | |
149 | trigger_allbutself_cpu_backtrace(); | |
150 | ||
151 | if (hardlockup_panic) | |
152 | nmi_panic(regs, "Hard LOCKUP"); | |
153 | ||
154 | __this_cpu_write(hard_watchdog_warn, true); | |
155 | return; | |
156 | } | |
157 | ||
158 | __this_cpu_write(hard_watchdog_warn, false); | |
159 | return; | |
160 | } | |
161 | ||
178b9f7a TG |
162 | static int hardlockup_detector_event_create(void) |
163 | { | |
164 | unsigned int cpu = smp_processor_id(); | |
165 | struct perf_event_attr *wd_attr; | |
166 | struct perf_event *evt; | |
167 | ||
168 | wd_attr = &wd_hw_attr; | |
169 | wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); | |
170 | ||
171 | /* Try to register using hardware perf events */ | |
172 | evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, | |
173 | watchdog_overflow_callback, NULL); | |
174 | if (IS_ERR(evt)) { | |
175 | pr_info("Perf event create on CPU %d failed with %ld\n", cpu, | |
176 | PTR_ERR(evt)); | |
177 | return PTR_ERR(evt); | |
178 | } | |
179 | this_cpu_write(watchdog_ev, evt); | |
180 | return 0; | |
181 | } | |
182 | ||
2a1b8ee4 TG |
183 | /** |
184 | * hardlockup_detector_perf_enable - Enable the local event | |
185 | */ | |
186 | void hardlockup_detector_perf_enable(void) | |
187 | { | |
188 | if (hardlockup_detector_event_create()) | |
189 | return; | |
190 | ||
146c9d0e TG |
191 | if (!watchdog_cpus++) |
192 | pr_info("Enabled. Permanently consumes one hw-PMU counter.\n"); | |
193 | ||
2a1b8ee4 TG |
194 | perf_event_enable(this_cpu_read(watchdog_ev)); |
195 | } | |
196 | ||
941154bd TG |
197 | /** |
198 | * hardlockup_detector_perf_disable - Disable the local event | |
199 | */ | |
200 | void hardlockup_detector_perf_disable(void) | |
73ce0511 | 201 | { |
941154bd | 202 | struct perf_event *event = this_cpu_read(watchdog_ev); |
73ce0511 BM |
203 | |
204 | if (event) { | |
205 | perf_event_disable(event); | |
941154bd | 206 | cpumask_set_cpu(smp_processor_id(), &dead_events_mask); |
146c9d0e | 207 | watchdog_cpus--; |
73ce0511 BM |
208 | } |
209 | } | |
d0b6e0a8 | 210 | |
941154bd TG |
211 | /** |
212 | * hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them | |
213 | * | |
214 | * Called from lockup_detector_cleanup(). Serialized by the caller. | |
215 | */ | |
216 | void hardlockup_detector_perf_cleanup(void) | |
217 | { | |
218 | int cpu; | |
219 | ||
220 | for_each_cpu(cpu, &dead_events_mask) { | |
a33d4484 | 221 | struct perf_event *event = per_cpu(watchdog_ev, cpu); |
941154bd | 222 | |
115ef3b7 TG |
223 | /* |
224 | * Required because for_each_cpu() reports unconditionally | |
225 | * CPU0 as set on UP kernels. Sigh. | |
226 | */ | |
227 | if (event) | |
228 | perf_event_release_kernel(event); | |
a33d4484 | 229 | per_cpu(watchdog_ev, cpu) = NULL; |
941154bd TG |
230 | } |
231 | cpumask_clear(&dead_events_mask); | |
232 | } | |
233 | ||
d0b6e0a8 PZ |
234 | /** |
235 | * hardlockup_detector_perf_stop - Globally stop watchdog events | |
236 | * | |
237 | * Special interface for x86 to handle the perf HT bug. | |
238 | */ | |
239 | void __init hardlockup_detector_perf_stop(void) | |
240 | { | |
241 | int cpu; | |
242 | ||
243 | lockdep_assert_cpus_held(); | |
244 | ||
245 | for_each_online_cpu(cpu) { | |
246 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
247 | ||
248 | if (event) | |
249 | perf_event_disable(event); | |
250 | } | |
251 | } | |
252 | ||
253 | /** | |
254 | * hardlockup_detector_perf_restart - Globally restart watchdog events | |
255 | * | |
256 | * Special interface for x86 to handle the perf HT bug. | |
257 | */ | |
258 | void __init hardlockup_detector_perf_restart(void) | |
259 | { | |
260 | int cpu; | |
261 | ||
262 | lockdep_assert_cpus_held(); | |
263 | ||
264 | if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED)) | |
265 | return; | |
266 | ||
267 | for_each_online_cpu(cpu) { | |
268 | struct perf_event *event = per_cpu(watchdog_ev, cpu); | |
269 | ||
270 | if (event) | |
271 | perf_event_enable(event); | |
272 | } | |
273 | } | |
178b9f7a TG |
274 | |
275 | /** | |
276 | * hardlockup_detector_perf_init - Probe whether NMI event is available at all | |
277 | */ | |
278 | int __init hardlockup_detector_perf_init(void) | |
279 | { | |
280 | int ret = hardlockup_detector_event_create(); | |
281 | ||
282 | if (ret) { | |
77c01d11 | 283 | pr_info("Perf NMI watchdog permanently disabled\n"); |
178b9f7a TG |
284 | } else { |
285 | perf_event_release_kernel(this_cpu_read(watchdog_ev)); | |
286 | this_cpu_write(watchdog_ev, NULL); | |
287 | } | |
288 | return ret; | |
289 | } |