a7f137c1933aa207175f8643bc19f503b09b6ea4
[sfrench/cifs-2.6.git] / kernel / watchdog_hld.c
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>
16 #include <linux/sched/debug.h>
17
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);
24 static DEFINE_PER_CPU(struct perf_event *, dead_event);
25 static struct cpumask dead_events_mask;
26
27 static unsigned long hardlockup_allcpu_dumped;
28 static unsigned int watchdog_cpus;
29
30 void arch_touch_nmi_watchdog(void)
31 {
32         /*
33          * Using __raw here because some code paths have
34          * preemption enabled.  If preemption is enabled
35          * then interrupts should be enabled too, in which
36          * case we shouldn't have to worry about the watchdog
37          * going off.
38          */
39         raw_cpu_write(watchdog_nmi_touch, true);
40 }
41 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
42
43 #ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMP
44 static DEFINE_PER_CPU(ktime_t, last_timestamp);
45 static DEFINE_PER_CPU(unsigned int, nmi_rearmed);
46 static ktime_t watchdog_hrtimer_sample_threshold __read_mostly;
47
48 void watchdog_update_hrtimer_threshold(u64 period)
49 {
50         /*
51          * The hrtimer runs with a period of (watchdog_threshold * 2) / 5
52          *
53          * So it runs effectively with 2.5 times the rate of the NMI
54          * watchdog. That means the hrtimer should fire 2-3 times before
55          * the NMI watchdog expires. The NMI watchdog on x86 is based on
56          * unhalted CPU cycles, so if Turbo-Mode is enabled the CPU cycles
57          * might run way faster than expected and the NMI fires in a
58          * smaller period than the one deduced from the nominal CPU
59          * frequency. Depending on the Turbo-Mode factor this might be fast
60          * enough to get the NMI period smaller than the hrtimer watchdog
61          * period and trigger false positives.
62          *
63          * The sample threshold is used to check in the NMI handler whether
64          * the minimum time between two NMI samples has elapsed. That
65          * prevents false positives.
66          *
67          * Set this to 4/5 of the actual watchdog threshold period so the
68          * hrtimer is guaranteed to fire at least once within the real
69          * watchdog threshold.
70          */
71         watchdog_hrtimer_sample_threshold = period * 2;
72 }
73
74 static bool watchdog_check_timestamp(void)
75 {
76         ktime_t delta, now = ktime_get_mono_fast_ns();
77
78         delta = now - __this_cpu_read(last_timestamp);
79         if (delta < watchdog_hrtimer_sample_threshold) {
80                 /*
81                  * If ktime is jiffies based, a stalled timer would prevent
82                  * jiffies from being incremented and the filter would look
83                  * at a stale timestamp and never trigger.
84                  */
85                 if (__this_cpu_inc_return(nmi_rearmed) < 10)
86                         return false;
87         }
88         __this_cpu_write(nmi_rearmed, 0);
89         __this_cpu_write(last_timestamp, now);
90         return true;
91 }
92 #else
93 static inline bool watchdog_check_timestamp(void)
94 {
95         return true;
96 }
97 #endif
98
99 static struct perf_event_attr wd_hw_attr = {
100         .type           = PERF_TYPE_HARDWARE,
101         .config         = PERF_COUNT_HW_CPU_CYCLES,
102         .size           = sizeof(struct perf_event_attr),
103         .pinned         = 1,
104         .disabled       = 1,
105 };
106
107 /* Callback function for perf event subsystem */
108 static void watchdog_overflow_callback(struct perf_event *event,
109                                        struct perf_sample_data *data,
110                                        struct pt_regs *regs)
111 {
112         /* Ensure the watchdog never gets throttled */
113         event->hw.interrupts = 0;
114
115         if (__this_cpu_read(watchdog_nmi_touch) == true) {
116                 __this_cpu_write(watchdog_nmi_touch, false);
117                 return;
118         }
119
120         if (!watchdog_check_timestamp())
121                 return;
122
123         /* check for a hardlockup
124          * This is done by making sure our timer interrupt
125          * is incrementing.  The timer interrupt should have
126          * fired multiple times before we overflow'd.  If it hasn't
127          * then this is a good indication the cpu is stuck
128          */
129         if (is_hardlockup()) {
130                 int this_cpu = smp_processor_id();
131
132                 /* only print hardlockups once */
133                 if (__this_cpu_read(hard_watchdog_warn) == true)
134                         return;
135
136                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
137                 print_modules();
138                 print_irqtrace_events(current);
139                 if (regs)
140                         show_regs(regs);
141                 else
142                         dump_stack();
143
144                 /*
145                  * Perform all-CPU dump only once to avoid multiple hardlockups
146                  * generating interleaving traces
147                  */
148                 if (sysctl_hardlockup_all_cpu_backtrace &&
149                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
150                         trigger_allbutself_cpu_backtrace();
151
152                 if (hardlockup_panic)
153                         nmi_panic(regs, "Hard LOCKUP");
154
155                 __this_cpu_write(hard_watchdog_warn, true);
156                 return;
157         }
158
159         __this_cpu_write(hard_watchdog_warn, false);
160         return;
161 }
162
163 static int hardlockup_detector_event_create(void)
164 {
165         unsigned int cpu = smp_processor_id();
166         struct perf_event_attr *wd_attr;
167         struct perf_event *evt;
168
169         wd_attr = &wd_hw_attr;
170         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
171
172         /* Try to register using hardware perf events */
173         evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
174                                                watchdog_overflow_callback, NULL);
175         if (IS_ERR(evt)) {
176                 pr_info("Perf event create on CPU %d failed with %ld\n", cpu,
177                         PTR_ERR(evt));
178                 return PTR_ERR(evt);
179         }
180         this_cpu_write(watchdog_ev, evt);
181         return 0;
182 }
183
184 /**
185  * hardlockup_detector_perf_enable - Enable the local event
186  */
187 void hardlockup_detector_perf_enable(void)
188 {
189         if (hardlockup_detector_event_create())
190                 return;
191
192         if (!watchdog_cpus++)
193                 pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
194
195         perf_event_enable(this_cpu_read(watchdog_ev));
196 }
197
198 /**
199  * hardlockup_detector_perf_disable - Disable the local event
200  */
201 void hardlockup_detector_perf_disable(void)
202 {
203         struct perf_event *event = this_cpu_read(watchdog_ev);
204
205         if (event) {
206                 perf_event_disable(event);
207                 this_cpu_write(watchdog_ev, NULL);
208                 this_cpu_write(dead_event, event);
209                 cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
210                 watchdog_cpus--;
211         }
212 }
213
214 /**
215  * hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them
216  *
217  * Called from lockup_detector_cleanup(). Serialized by the caller.
218  */
219 void hardlockup_detector_perf_cleanup(void)
220 {
221         int cpu;
222
223         for_each_cpu(cpu, &dead_events_mask) {
224                 struct perf_event *event = per_cpu(dead_event, cpu);
225
226                 /*
227                  * Required because for_each_cpu() reports  unconditionally
228                  * CPU0 as set on UP kernels. Sigh.
229                  */
230                 if (event)
231                         perf_event_release_kernel(event);
232                 per_cpu(dead_event, cpu) = NULL;
233         }
234         cpumask_clear(&dead_events_mask);
235 }
236
237 /**
238  * hardlockup_detector_perf_stop - Globally stop watchdog events
239  *
240  * Special interface for x86 to handle the perf HT bug.
241  */
242 void __init hardlockup_detector_perf_stop(void)
243 {
244         int cpu;
245
246         lockdep_assert_cpus_held();
247
248         for_each_online_cpu(cpu) {
249                 struct perf_event *event = per_cpu(watchdog_ev, cpu);
250
251                 if (event)
252                         perf_event_disable(event);
253         }
254 }
255
256 /**
257  * hardlockup_detector_perf_restart - Globally restart watchdog events
258  *
259  * Special interface for x86 to handle the perf HT bug.
260  */
261 void __init hardlockup_detector_perf_restart(void)
262 {
263         int cpu;
264
265         lockdep_assert_cpus_held();
266
267         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
268                 return;
269
270         for_each_online_cpu(cpu) {
271                 struct perf_event *event = per_cpu(watchdog_ev, cpu);
272
273                 if (event)
274                         perf_event_enable(event);
275         }
276 }
277
278 /**
279  * hardlockup_detector_perf_init - Probe whether NMI event is available at all
280  */
281 int __init hardlockup_detector_perf_init(void)
282 {
283         int ret = hardlockup_detector_event_create();
284
285         if (ret) {
286                 pr_info("Perf NMI watchdog permanently disabled\n");
287         } else {
288                 perf_event_release_kernel(this_cpu_read(watchdog_ev));
289                 this_cpu_write(watchdog_ev, NULL);
290         }
291         return ret;
292 }