Merge tag 'renesas-dt-fixes-for-v4.15' of https://git.kernel.org/pub/scm/linux/kernel...
[sfrench/cifs-2.6.git] / kernel / watchdog_hld.c
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Detect hard lockups on a system
4  *
5  * started by Don Zickus, Copyright (C) 2010 Red Hat, Inc.
6  *
7  * Note: Most of this code is borrowed heavily from the original softlockup
8  * detector, so thanks to Ingo for the initial implementation.
9  * Some chunks also taken from the old x86-specific nmi watchdog code, thanks
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(bool, hard_watchdog_warn);
24 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
25 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
26 static DEFINE_PER_CPU(struct perf_event *, dead_event);
27 static struct cpumask dead_events_mask;
28
29 static unsigned long hardlockup_allcpu_dumped;
30 static atomic_t watchdog_cpus = ATOMIC_INIT(0);
31
32 void arch_touch_nmi_watchdog(void)
33 {
34         /*
35          * Using __raw here because some code paths have
36          * preemption enabled.  If preemption is enabled
37          * then interrupts should be enabled too, in which
38          * case we shouldn't have to worry about the watchdog
39          * going off.
40          */
41         raw_cpu_write(watchdog_nmi_touch, true);
42 }
43 EXPORT_SYMBOL(arch_touch_nmi_watchdog);
44
45 #ifdef CONFIG_HARDLOCKUP_CHECK_TIMESTAMP
46 static DEFINE_PER_CPU(ktime_t, last_timestamp);
47 static DEFINE_PER_CPU(unsigned int, nmi_rearmed);
48 static ktime_t watchdog_hrtimer_sample_threshold __read_mostly;
49
50 void watchdog_update_hrtimer_threshold(u64 period)
51 {
52         /*
53          * The hrtimer runs with a period of (watchdog_threshold * 2) / 5
54          *
55          * So it runs effectively with 2.5 times the rate of the NMI
56          * watchdog. That means the hrtimer should fire 2-3 times before
57          * the NMI watchdog expires. The NMI watchdog on x86 is based on
58          * unhalted CPU cycles, so if Turbo-Mode is enabled the CPU cycles
59          * might run way faster than expected and the NMI fires in a
60          * smaller period than the one deduced from the nominal CPU
61          * frequency. Depending on the Turbo-Mode factor this might be fast
62          * enough to get the NMI period smaller than the hrtimer watchdog
63          * period and trigger false positives.
64          *
65          * The sample threshold is used to check in the NMI handler whether
66          * the minimum time between two NMI samples has elapsed. That
67          * prevents false positives.
68          *
69          * Set this to 4/5 of the actual watchdog threshold period so the
70          * hrtimer is guaranteed to fire at least once within the real
71          * watchdog threshold.
72          */
73         watchdog_hrtimer_sample_threshold = period * 2;
74 }
75
76 static bool watchdog_check_timestamp(void)
77 {
78         ktime_t delta, now = ktime_get_mono_fast_ns();
79
80         delta = now - __this_cpu_read(last_timestamp);
81         if (delta < watchdog_hrtimer_sample_threshold) {
82                 /*
83                  * If ktime is jiffies based, a stalled timer would prevent
84                  * jiffies from being incremented and the filter would look
85                  * at a stale timestamp and never trigger.
86                  */
87                 if (__this_cpu_inc_return(nmi_rearmed) < 10)
88                         return false;
89         }
90         __this_cpu_write(nmi_rearmed, 0);
91         __this_cpu_write(last_timestamp, now);
92         return true;
93 }
94 #else
95 static inline bool watchdog_check_timestamp(void)
96 {
97         return true;
98 }
99 #endif
100
101 static struct perf_event_attr wd_hw_attr = {
102         .type           = PERF_TYPE_HARDWARE,
103         .config         = PERF_COUNT_HW_CPU_CYCLES,
104         .size           = sizeof(struct perf_event_attr),
105         .pinned         = 1,
106         .disabled       = 1,
107 };
108
109 /* Callback function for perf event subsystem */
110 static void watchdog_overflow_callback(struct perf_event *event,
111                                        struct perf_sample_data *data,
112                                        struct pt_regs *regs)
113 {
114         /* Ensure the watchdog never gets throttled */
115         event->hw.interrupts = 0;
116
117         if (__this_cpu_read(watchdog_nmi_touch) == true) {
118                 __this_cpu_write(watchdog_nmi_touch, false);
119                 return;
120         }
121
122         if (!watchdog_check_timestamp())
123                 return;
124
125         /* check for a hardlockup
126          * This is done by making sure our timer interrupt
127          * is incrementing.  The timer interrupt should have
128          * fired multiple times before we overflow'd.  If it hasn't
129          * then this is a good indication the cpu is stuck
130          */
131         if (is_hardlockup()) {
132                 int this_cpu = smp_processor_id();
133
134                 /* only print hardlockups once */
135                 if (__this_cpu_read(hard_watchdog_warn) == true)
136                         return;
137
138                 pr_emerg("Watchdog detected hard LOCKUP on cpu %d", this_cpu);
139                 print_modules();
140                 print_irqtrace_events(current);
141                 if (regs)
142                         show_regs(regs);
143                 else
144                         dump_stack();
145
146                 /*
147                  * Perform all-CPU dump only once to avoid multiple hardlockups
148                  * generating interleaving traces
149                  */
150                 if (sysctl_hardlockup_all_cpu_backtrace &&
151                                 !test_and_set_bit(0, &hardlockup_allcpu_dumped))
152                         trigger_allbutself_cpu_backtrace();
153
154                 if (hardlockup_panic)
155                         nmi_panic(regs, "Hard LOCKUP");
156
157                 __this_cpu_write(hard_watchdog_warn, true);
158                 return;
159         }
160
161         __this_cpu_write(hard_watchdog_warn, false);
162         return;
163 }
164
165 static int hardlockup_detector_event_create(void)
166 {
167         unsigned int cpu = smp_processor_id();
168         struct perf_event_attr *wd_attr;
169         struct perf_event *evt;
170
171         wd_attr = &wd_hw_attr;
172         wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh);
173
174         /* Try to register using hardware perf events */
175         evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL,
176                                                watchdog_overflow_callback, NULL);
177         if (IS_ERR(evt)) {
178                 pr_info("Perf event create on CPU %d failed with %ld\n", cpu,
179                         PTR_ERR(evt));
180                 return PTR_ERR(evt);
181         }
182         this_cpu_write(watchdog_ev, evt);
183         return 0;
184 }
185
186 /**
187  * hardlockup_detector_perf_enable - Enable the local event
188  */
189 void hardlockup_detector_perf_enable(void)
190 {
191         if (hardlockup_detector_event_create())
192                 return;
193
194         /* use original value for check */
195         if (!atomic_fetch_inc(&watchdog_cpus))
196                 pr_info("Enabled. Permanently consumes one hw-PMU counter.\n");
197
198         perf_event_enable(this_cpu_read(watchdog_ev));
199 }
200
201 /**
202  * hardlockup_detector_perf_disable - Disable the local event
203  */
204 void hardlockup_detector_perf_disable(void)
205 {
206         struct perf_event *event = this_cpu_read(watchdog_ev);
207
208         if (event) {
209                 perf_event_disable(event);
210                 this_cpu_write(watchdog_ev, NULL);
211                 this_cpu_write(dead_event, event);
212                 cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
213                 atomic_dec(&watchdog_cpus);
214         }
215 }
216
217 /**
218  * hardlockup_detector_perf_cleanup - Cleanup disabled events and destroy them
219  *
220  * Called from lockup_detector_cleanup(). Serialized by the caller.
221  */
222 void hardlockup_detector_perf_cleanup(void)
223 {
224         int cpu;
225
226         for_each_cpu(cpu, &dead_events_mask) {
227                 struct perf_event *event = per_cpu(dead_event, cpu);
228
229                 /*
230                  * Required because for_each_cpu() reports  unconditionally
231                  * CPU0 as set on UP kernels. Sigh.
232                  */
233                 if (event)
234                         perf_event_release_kernel(event);
235                 per_cpu(dead_event, cpu) = NULL;
236         }
237         cpumask_clear(&dead_events_mask);
238 }
239
240 /**
241  * hardlockup_detector_perf_stop - Globally stop watchdog events
242  *
243  * Special interface for x86 to handle the perf HT bug.
244  */
245 void __init hardlockup_detector_perf_stop(void)
246 {
247         int cpu;
248
249         lockdep_assert_cpus_held();
250
251         for_each_online_cpu(cpu) {
252                 struct perf_event *event = per_cpu(watchdog_ev, cpu);
253
254                 if (event)
255                         perf_event_disable(event);
256         }
257 }
258
259 /**
260  * hardlockup_detector_perf_restart - Globally restart watchdog events
261  *
262  * Special interface for x86 to handle the perf HT bug.
263  */
264 void __init hardlockup_detector_perf_restart(void)
265 {
266         int cpu;
267
268         lockdep_assert_cpus_held();
269
270         if (!(watchdog_enabled & NMI_WATCHDOG_ENABLED))
271                 return;
272
273         for_each_online_cpu(cpu) {
274                 struct perf_event *event = per_cpu(watchdog_ev, cpu);
275
276                 if (event)
277                         perf_event_enable(event);
278         }
279 }
280
281 /**
282  * hardlockup_detector_perf_init - Probe whether NMI event is available at all
283  */
284 int __init hardlockup_detector_perf_init(void)
285 {
286         int ret = hardlockup_detector_event_create();
287
288         if (ret) {
289                 pr_info("Perf NMI watchdog permanently disabled\n");
290         } else {
291                 perf_event_release_kernel(this_cpu_read(watchdog_ev));
292                 this_cpu_write(watchdog_ev, NULL);
293         }
294         return ret;
295 }