1	// SPDX-License-Identifier: GPL-2.0
2	/*
3	* Kernel internal timers
4	*
5	* Copyright (C) 1991, 1992 Linus Torvalds
6	*
7	* 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
8	*
9	* 1997-09-10 Updated NTP code according to technical memorandum Jan '96
10	* "A Kernel Model for Precision Timekeeping" by Dave Mills
11	* 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
12	* serialize accesses to xtime/lost_ticks).
13	* Copyright (C) 1998 Andrea Arcangeli
14	* 1999-03-10 Improved NTP compatibility by Ulrich Windl
15	* 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
16	* 2000-10-05 Implemented scalable SMP per-CPU timer handling.
17	* Copyright (C) 2000, 2001, 2002 Ingo Molnar
18	* Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
19	*/
20
21	#include <linux/kernel_stat.h>
22	#include <linux/export.h>
23	#include <linux/interrupt.h>
24	#include <linux/percpu.h>
25	#include <linux/init.h>
26	#include <linux/mm.h>
27	#include <linux/swap.h>
28	#include <linux/pid_namespace.h>
29	#include <linux/notifier.h>
30	#include <linux/thread_info.h>
31	#include <linux/time.h>
32	#include <linux/jiffies.h>
33	#include <linux/posix-timers.h>
34	#include <linux/cpu.h>
35	#include <linux/syscalls.h>
36	#include <linux/delay.h>
37	#include <linux/tick.h>
38	#include <linux/kallsyms.h>
39	#include <linux/irq_work.h>
40	#include <linux/sched/signal.h>
41	#include <linux/sched/sysctl.h>
42	#include <linux/sched/nohz.h>
43	#include <linux/sched/debug.h>
44	#include <linux/slab.h>
45	#include <linux/compat.h>
46	#include <linux/random.h>
47	#include <linux/sysctl.h>
48
49	#include <linux/uaccess.h>
50	#include <asm/unistd.h>
51	#include <asm/div64.h>
52	#include <asm/timex.h>
53	#include <asm/io.h>
54
55	#include "tick-internal.h"
56
57	#define CREATE_TRACE_POINTS
58	#include <trace/events/timer.h>
59
60	__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
61
62	EXPORT_SYMBOL(jiffies_64);
63
64	/*
65	* The timer wheel has LVL_DEPTH array levels. Each level provides an array of
66	* LVL_SIZE buckets. Each level is driven by its own clock and therefor each
67	* level has a different granularity.
68	*
69	* The level granularity is: LVL_CLK_DIV ^ lvl
70	* The level clock frequency is: HZ / (LVL_CLK_DIV ^ level)
71	*
72	* The array level of a newly armed timer depends on the relative expiry
73	* time. The farther the expiry time is away the higher the array level and
74	* therefor the granularity becomes.
75	*
76	* Contrary to the original timer wheel implementation, which aims for 'exact'
77	* expiry of the timers, this implementation removes the need for recascading
78	* the timers into the lower array levels. The previous 'classic' timer wheel
79	* implementation of the kernel already violated the 'exact' expiry by adding
80	* slack to the expiry time to provide batched expiration. The granularity
81	* levels provide implicit batching.
82	*
83	* This is an optimization of the original timer wheel implementation for the
84	* majority of the timer wheel use cases: timeouts. The vast majority of
85	* timeout timers (networking, disk I/O ...) are canceled before expiry. If
86	* the timeout expires it indicates that normal operation is disturbed, so it
87	* does not matter much whether the timeout comes with a slight delay.
88	*
89	* The only exception to this are networking timers with a small expiry
90	* time. They rely on the granularity. Those fit into the first wheel level,
91	* which has HZ granularity.
92	*
93	* We don't have cascading anymore. timers with a expiry time above the
94	* capacity of the last wheel level are force expired at the maximum timeout
95	* value of the last wheel level. From data sampling we know that the maximum
96	* value observed is 5 days (network connection tracking), so this should not
97	* be an issue.
98	*
99	* The currently chosen array constants values are a good compromise between
100	* array size and granularity.
101	*
102	* This results in the following granularity and range levels:
103	*
104	* HZ 1000 steps
105	* Level Offset Granularity Range
106	* 0 0 1 ms 0 ms - 63 ms
107	* 1 64 8 ms 64 ms - 511 ms
108	* 2 128 64 ms 512 ms - 4095 ms (512ms - ~4s)
109	* 3 192 512 ms 4096 ms - 32767 ms (~4s - ~32s)
110	* 4 256 4096 ms (~4s) 32768 ms - 262143 ms (~32s - ~4m)
111	* 5 320 32768 ms (~32s) 262144 ms - 2097151 ms (~4m - ~34m)
112	* 6 384 262144 ms (~4m) 2097152 ms - 16777215 ms (~34m - ~4h)
113	* 7 448 2097152 ms (~34m) 16777216 ms - 134217727 ms (~4h - ~1d)
114	* 8 512 16777216 ms (~4h) 134217728 ms - 1073741822 ms (~1d - ~12d)
115	*
116	* HZ 300
117	* Level Offset Granularity Range
118	* 0 0 3 ms 0 ms - 210 ms
119	* 1 64 26 ms 213 ms - 1703 ms (213ms - ~1s)
120	* 2 128 213 ms 1706 ms - 13650 ms (~1s - ~13s)
121	* 3 192 1706 ms (~1s) 13653 ms - 109223 ms (~13s - ~1m)
122	* 4 256 13653 ms (~13s) 109226 ms - 873810 ms (~1m - ~14m)
123	* 5 320 109226 ms (~1m) 873813 ms - 6990503 ms (~14m - ~1h)
124	* 6 384 873813 ms (~14m) 6990506 ms - 55924050 ms (~1h - ~15h)
125	* 7 448 6990506 ms (~1h) 55924053 ms - 447392423 ms (~15h - ~5d)
126	* 8 512 55924053 ms (~15h) 447392426 ms - 3579139406 ms (~5d - ~41d)
127	*
128	* HZ 250
129	* Level Offset Granularity Range
130	* 0 0 4 ms 0 ms - 255 ms
131	* 1 64 32 ms 256 ms - 2047 ms (256ms - ~2s)
132	* 2 128 256 ms 2048 ms - 16383 ms (~2s - ~16s)
133	* 3 192 2048 ms (~2s) 16384 ms - 131071 ms (~16s - ~2m)
134	* 4 256 16384 ms (~16s) 131072 ms - 1048575 ms (~2m - ~17m)
135	* 5 320 131072 ms (~2m) 1048576 ms - 8388607 ms (~17m - ~2h)
136	* 6 384 1048576 ms (~17m) 8388608 ms - 67108863 ms (~2h - ~18h)
137	* 7 448 8388608 ms (~2h) 67108864 ms - 536870911 ms (~18h - ~6d)
138	* 8 512 67108864 ms (~18h) 536870912 ms - 4294967288 ms (~6d - ~49d)
139	*
140	* HZ 100
141	* Level Offset Granularity Range
142	* 0 0 10 ms 0 ms - 630 ms
143	* 1 64 80 ms 640 ms - 5110 ms (640ms - ~5s)
144	* 2 128 640 ms 5120 ms - 40950 ms (~5s - ~40s)
145	* 3 192 5120 ms (~5s) 40960 ms - 327670 ms (~40s - ~5m)
146	* 4 256 40960 ms (~40s) 327680 ms - 2621430 ms (~5m - ~43m)
147	* 5 320 327680 ms (~5m) 2621440 ms - 20971510 ms (~43m - ~5h)
148	* 6 384 2621440 ms (~43m) 20971520 ms - 167772150 ms (~5h - ~1d)
149	* 7 448 20971520 ms (~5h) 167772160 ms - 1342177270 ms (~1d - ~15d)
150	*/
151
152	/* Clock divisor for the next level */
153	#define LVL_CLK_SHIFT 3
154	#define LVL_CLK_DIV (1UL << LVL_CLK_SHIFT)
155	#define LVL_CLK_MASK (LVL_CLK_DIV - 1)
156	#define LVL_SHIFT(n) ((n) * LVL_CLK_SHIFT)
157	#define LVL_GRAN(n) (1UL << LVL_SHIFT(n))
158
159	/*
160	* The time start value for each level to select the bucket at enqueue
161	* time. We start from the last possible delta of the previous level
162	* so that we can later add an extra LVL_GRAN(n) to n (see calc_index()).
163	*/
164	#define LVL_START(n) ((LVL_SIZE - 1) << (((n) - 1) * LVL_CLK_SHIFT))
165
166	/* Size of each clock level */
167	#define LVL_BITS 6
168	#define LVL_SIZE (1UL << LVL_BITS)
169	#define LVL_MASK (LVL_SIZE - 1)
170	#define LVL_OFFS(n) ((n) * LVL_SIZE)
171
172	/* Level depth */
173	#if HZ > 100
174	# define LVL_DEPTH 9
175	# else
176	# define LVL_DEPTH 8
177	#endif
178
179	/* The cutoff (max. capacity of the wheel) */
180	#define WHEEL_TIMEOUT_CUTOFF (LVL_START(LVL_DEPTH))
181	#define WHEEL_TIMEOUT_MAX (WHEEL_TIMEOUT_CUTOFF - LVL_GRAN(LVL_DEPTH - 1))
182
183	/*
184	* The resulting wheel size. If NOHZ is configured we allocate two
185	* wheels so we have a separate storage for the deferrable timers.
186	*/
187	#define WHEEL_SIZE (LVL_SIZE * LVL_DEPTH)
188
189	#ifdef CONFIG_NO_HZ_COMMON
190	# define NR_BASES 2
191	# define BASE_STD 0
192	# define BASE_DEF 1
193	#else
194	# define NR_BASES 1
195	# define BASE_STD 0
196	# define BASE_DEF 0
197	#endif
198
199	struct timer_base {
200	raw_spinlock_t lock;
201	struct timer_list *running_timer;
202	#ifdef CONFIG_PREEMPT_RT
203	spinlock_t expiry_lock;
204	atomic_t timer_waiters;
205	#endif
206	unsigned long clk;
207	unsigned long next_expiry;
208	unsigned int cpu;
209	bool next_expiry_recalc;
210	bool is_idle;
211	bool timers_pending;
212	DECLARE_BITMAP(pending_map, WHEEL_SIZE);
213	struct hlist_head vectors[WHEEL_SIZE];
214	} ____cacheline_aligned;
215
216	static DEFINE_PER_CPU(struct timer_base, timer_bases[NR_BASES]);
217
218	#ifdef CONFIG_NO_HZ_COMMON
219
220	static DEFINE_STATIC_KEY_FALSE(timers_nohz_active);
221	static DEFINE_MUTEX(timer_keys_mutex);
222
223	static void timer_update_keys(struct work_struct *work);
224	static DECLARE_WORK(timer_update_work, timer_update_keys);
225
226	#ifdef CONFIG_SMP
227	static unsigned int sysctl_timer_migration = 1;
228
229	DEFINE_STATIC_KEY_FALSE(timers_migration_enabled);
230
231	static void timers_update_migration(void)
232	{
233	if (sysctl_timer_migration && tick_nohz_active)
234	static_branch_enable(&timers_migration_enabled);
235	else
236	static_branch_disable(&timers_migration_enabled);
237	}
238
239	#ifdef CONFIG_SYSCTL
240	static int timer_migration_handler(struct ctl_table *table, int write,
241	void *buffer, size_t *lenp, loff_t *ppos)
242	{
243	int ret;
244
245	mutex_lock(&timer_keys_mutex);
246	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
247	if (!ret && write)
248	timers_update_migration();
249	mutex_unlock(lock: &timer_keys_mutex);
250	return ret;
251	}
252
253	static struct ctl_table timer_sysctl[] = {
254	{
255	.procname = "timer_migration",
256	.data = &sysctl_timer_migration,
257	.maxlen = sizeof(unsigned int),
258	.mode = 0644,
259	.proc_handler = timer_migration_handler,
260	.extra1 = SYSCTL_ZERO,
261	.extra2 = SYSCTL_ONE,
262	},
263	{}
264	};
265
266	static int __init timer_sysctl_init(void)
267	{
268	register_sysctl("kernel", timer_sysctl);
269	return 0;
270	}
271	device_initcall(timer_sysctl_init);
272	#endif /* CONFIG_SYSCTL */
273	#else /* CONFIG_SMP */
274	static inline void timers_update_migration(void) { }
275	#endif /* !CONFIG_SMP */
276
277	static void timer_update_keys(struct work_struct *work)
278	{
279	mutex_lock(&timer_keys_mutex);
280	timers_update_migration();
281	static_branch_enable(&timers_nohz_active);
282	mutex_unlock(lock: &timer_keys_mutex);
283	}
284
285	void timers_update_nohz(void)
286	{
287	schedule_work(work: &timer_update_work);
288	}
289
290	static inline bool is_timers_nohz_active(void)
291	{
292	return static_branch_unlikely(&timers_nohz_active);
293	}
294	#else
295	static inline bool is_timers_nohz_active(void) { return false; }
296	#endif /* NO_HZ_COMMON */
297
298	static unsigned long round_jiffies_common(unsigned long j, int cpu,
299	bool force_up)
300	{
301	int rem;
302	unsigned long original = j;
303
304	/*
305	* We don't want all cpus firing their timers at once hitting the
306	* same lock or cachelines, so we skew each extra cpu with an extra
307	* 3 jiffies. This 3 jiffies came originally from the mm/ code which
308	* already did this.
309	* The skew is done by adding 3*cpunr, then round, then subtract this
310	* extra offset again.
311	*/
312	j += cpu * 3;
313
314	rem = j % HZ;
315
316	/*
317	* If the target jiffie is just after a whole second (which can happen
318	* due to delays of the timer irq, long irq off times etc etc) then
319	* we should round down to the whole second, not up. Use 1/4th second
320	* as cutoff for this rounding as an extreme upper bound for this.
321	* But never round down if @force_up is set.
322	*/
323	if (rem < HZ/4 && !force_up) /* round down */
324	j = j - rem;
325	else /* round up */
326	j = j - rem + HZ;
327
328	/* now that we have rounded, subtract the extra skew again */
329	j -= cpu * 3;
330
331	/*
332	* Make sure j is still in the future. Otherwise return the
333	* unmodified value.
334	*/
335	return time_is_after_jiffies(j) ? j : original;
336	}
337
338	/**
339	* __round_jiffies - function to round jiffies to a full second
340	* @j: the time in (absolute) jiffies that should be rounded
341	* @cpu: the processor number on which the timeout will happen
342	*
343	* __round_jiffies() rounds an absolute time in the future (in jiffies)
344	* up or down to (approximately) full seconds. This is useful for timers
345	* for which the exact time they fire does not matter too much, as long as
346	* they fire approximately every X seconds.
347	*
348	* By rounding these timers to whole seconds, all such timers will fire
349	* at the same time, rather than at various times spread out. The goal
350	* of this is to have the CPU wake up less, which saves power.
351	*
352	* The exact rounding is skewed for each processor to avoid all
353	* processors firing at the exact same time, which could lead
354	* to lock contention or spurious cache line bouncing.
355	*
356	* The return value is the rounded version of the @j parameter.
357	*/
358	unsigned long __round_jiffies(unsigned long j, int cpu)
359	{
360	return round_jiffies_common(j, cpu, force_up: false);
361	}
362	EXPORT_SYMBOL_GPL(__round_jiffies);
363
364	/**
365	* __round_jiffies_relative - function to round jiffies to a full second
366	* @j: the time in (relative) jiffies that should be rounded
367	* @cpu: the processor number on which the timeout will happen
368	*
369	* __round_jiffies_relative() rounds a time delta in the future (in jiffies)
370	* up or down to (approximately) full seconds. This is useful for timers
371	* for which the exact time they fire does not matter too much, as long as
372	* they fire approximately every X seconds.
373	*
374	* By rounding these timers to whole seconds, all such timers will fire
375	* at the same time, rather than at various times spread out. The goal
376	* of this is to have the CPU wake up less, which saves power.
377	*
378	* The exact rounding is skewed for each processor to avoid all
379	* processors firing at the exact same time, which could lead
380	* to lock contention or spurious cache line bouncing.
381	*
382	* The return value is the rounded version of the @j parameter.
383	*/
384	unsigned long __round_jiffies_relative(unsigned long j, int cpu)
385	{
386	unsigned long j0 = jiffies;
387
388	/* Use j0 because jiffies might change while we run */
389	return round_jiffies_common(j: j + j0, cpu, force_up: false) - j0;
390	}
391	EXPORT_SYMBOL_GPL(__round_jiffies_relative);
392
393	/**
394	* round_jiffies - function to round jiffies to a full second
395	* @j: the time in (absolute) jiffies that should be rounded
396	*
397	* round_jiffies() rounds an absolute time in the future (in jiffies)
398	* up or down to (approximately) full seconds. This is useful for timers
399	* for which the exact time they fire does not matter too much, as long as
400	* they fire approximately every X seconds.
401	*
402	* By rounding these timers to whole seconds, all such timers will fire
403	* at the same time, rather than at various times spread out. The goal
404	* of this is to have the CPU wake up less, which saves power.
405	*
406	* The return value is the rounded version of the @j parameter.
407	*/
408	unsigned long round_jiffies(unsigned long j)
409	{
410	return round_jiffies_common(j, raw_smp_processor_id(), force_up: false);
411	}
412	EXPORT_SYMBOL_GPL(round_jiffies);
413
414	/**
415	* round_jiffies_relative - function to round jiffies to a full second
416	* @j: the time in (relative) jiffies that should be rounded
417	*
418	* round_jiffies_relative() rounds a time delta in the future (in jiffies)
419	* up or down to (approximately) full seconds. This is useful for timers
420	* for which the exact time they fire does not matter too much, as long as
421	* they fire approximately every X seconds.
422	*
423	* By rounding these timers to whole seconds, all such timers will fire
424	* at the same time, rather than at various times spread out. The goal
425	* of this is to have the CPU wake up less, which saves power.
426	*
427	* The return value is the rounded version of the @j parameter.
428	*/
429	unsigned long round_jiffies_relative(unsigned long j)
430	{
431	return __round_jiffies_relative(j, raw_smp_processor_id());
432	}
433	EXPORT_SYMBOL_GPL(round_jiffies_relative);
434
435	/**
436	* __round_jiffies_up - function to round jiffies up to a full second
437	* @j: the time in (absolute) jiffies that should be rounded
438	* @cpu: the processor number on which the timeout will happen
439	*
440	* This is the same as __round_jiffies() except that it will never
441	* round down. This is useful for timeouts for which the exact time
442	* of firing does not matter too much, as long as they don't fire too
443	* early.
444	*/
445	unsigned long __round_jiffies_up(unsigned long j, int cpu)
446	{
447	return round_jiffies_common(j, cpu, force_up: true);
448	}
449	EXPORT_SYMBOL_GPL(__round_jiffies_up);
450
451	/**
452	* __round_jiffies_up_relative - function to round jiffies up to a full second
453	* @j: the time in (relative) jiffies that should be rounded
454	* @cpu: the processor number on which the timeout will happen
455	*
456	* This is the same as __round_jiffies_relative() except that it will never
457	* round down. This is useful for timeouts for which the exact time
458	* of firing does not matter too much, as long as they don't fire too
459	* early.
460	*/
461	unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
462	{
463	unsigned long j0 = jiffies;
464
465	/* Use j0 because jiffies might change while we run */
466	return round_jiffies_common(j: j + j0, cpu, force_up: true) - j0;
467	}
468	EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
469
470	/**
471	* round_jiffies_up - function to round jiffies up to a full second
472	* @j: the time in (absolute) jiffies that should be rounded
473	*
474	* This is the same as round_jiffies() except that it will never
475	* round down. This is useful for timeouts for which the exact time
476	* of firing does not matter too much, as long as they don't fire too
477	* early.
478	*/
479	unsigned long round_jiffies_up(unsigned long j)
480	{
481	return round_jiffies_common(j, raw_smp_processor_id(), force_up: true);
482	}
483	EXPORT_SYMBOL_GPL(round_jiffies_up);
484
485	/**
486	* round_jiffies_up_relative - function to round jiffies up to a full second
487	* @j: the time in (relative) jiffies that should be rounded
488	*
489	* This is the same as round_jiffies_relative() except that it will never
490	* round down. This is useful for timeouts for which the exact time
491	* of firing does not matter too much, as long as they don't fire too
492	* early.
493	*/
494	unsigned long round_jiffies_up_relative(unsigned long j)
495	{
496	return __round_jiffies_up_relative(j, raw_smp_processor_id());
497	}
498	EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
499
500
501	static inline unsigned int timer_get_idx(struct timer_list *timer)
502	{
503	return (timer->flags & TIMER_ARRAYMASK) >> TIMER_ARRAYSHIFT;
504	}
505
506	static inline void timer_set_idx(struct timer_list *timer, unsigned int idx)
507	{
508	timer->flags = (timer->flags & ~TIMER_ARRAYMASK) |
509	idx << TIMER_ARRAYSHIFT;
510	}
511
512	/*
513	* Helper function to calculate the array index for a given expiry
514	* time.
515	*/
516	static inline unsigned calc_index(unsigned long expires, unsigned lvl,
517	unsigned long *bucket_expiry)
518	{
519
520	/*
521	* The timer wheel has to guarantee that a timer does not fire
522	* early. Early expiry can happen due to:
523	* - Timer is armed at the edge of a tick
524	* - Truncation of the expiry time in the outer wheel levels
525	*
526	* Round up with level granularity to prevent this.
527	*/
528	expires = (expires >> LVL_SHIFT(lvl)) + 1;
529	*bucket_expiry = expires << LVL_SHIFT(lvl);
530	return LVL_OFFS(lvl) + (expires & LVL_MASK);
531	}
532
533	static int calc_wheel_index(unsigned long expires, unsigned long clk,
534	unsigned long *bucket_expiry)
535	{
536	unsigned long delta = expires - clk;
537	unsigned int idx;
538
539	if (delta < LVL_START(1)) {
540	idx = calc_index(expires, lvl: 0, bucket_expiry);
541	} else if (delta < LVL_START(2)) {
542	idx = calc_index(expires, lvl: 1, bucket_expiry);
543	} else if (delta < LVL_START(3)) {
544	idx = calc_index(expires, lvl: 2, bucket_expiry);
545	} else if (delta < LVL_START(4)) {
546	idx = calc_index(expires, lvl: 3, bucket_expiry);
547	} else if (delta < LVL_START(5)) {
548	idx = calc_index(expires, lvl: 4, bucket_expiry);
549	} else if (delta < LVL_START(6)) {
550	idx = calc_index(expires, lvl: 5, bucket_expiry);
551	} else if (delta < LVL_START(7)) {
552	idx = calc_index(expires, lvl: 6, bucket_expiry);
553	} else if (LVL_DEPTH > 8 && delta < LVL_START(8)) {
554	idx = calc_index(expires, lvl: 7, bucket_expiry);
555	} else if ((long) delta < 0) {
556	idx = clk & LVL_MASK;
557	*bucket_expiry = clk;
558	} else {
559	/*
560	* Force expire obscene large timeouts to expire at the
561	* capacity limit of the wheel.
562	*/
563	if (delta >= WHEEL_TIMEOUT_CUTOFF)
564	expires = clk + WHEEL_TIMEOUT_MAX;
565
566	idx = calc_index(expires, LVL_DEPTH - 1, bucket_expiry);
567	}
568	return idx;
569	}
570
571	static void
572	trigger_dyntick_cpu(struct timer_base *base, struct timer_list *timer)
573	{
574	if (!is_timers_nohz_active())
575	return;
576
577	/*
578	* TODO: This wants some optimizing similar to the code below, but we
579	* will do that when we switch from push to pull for deferrable timers.
580	*/
581	if (timer->flags & TIMER_DEFERRABLE) {
582	if (tick_nohz_full_cpu(cpu: base->cpu))
583	wake_up_nohz_cpu(cpu: base->cpu);
584	return;
585	}
586
587	/*
588	* We might have to IPI the remote CPU if the base is idle and the
589	* timer is not deferrable. If the other CPU is on the way to idle
590	* then it can't set base->is_idle as we hold the base lock:
591	*/
592	if (base->is_idle)
593	wake_up_nohz_cpu(cpu: base->cpu);
594	}
595
596	/*
597	* Enqueue the timer into the hash bucket, mark it pending in
598	* the bitmap, store the index in the timer flags then wake up
599	* the target CPU if needed.
600	*/
601	static void enqueue_timer(struct timer_base *base, struct timer_list *timer,
602	unsigned int idx, unsigned long bucket_expiry)
603	{
604
605	hlist_add_head(n: &timer->entry, h: base->vectors + idx);
606	__set_bit(idx, base->pending_map);
607	timer_set_idx(timer, idx);
608
609	trace_timer_start(timer, expires: timer->expires, flags: timer->flags);
610
611	/*
612	* Check whether this is the new first expiring timer. The
613	* effective expiry time of the timer is required here
614	* (bucket_expiry) instead of timer->expires.
615	*/
616	if (time_before(bucket_expiry, base->next_expiry)) {
617	/*
618	* Set the next expiry time and kick the CPU so it
619	* can reevaluate the wheel:
620	*/
621	base->next_expiry = bucket_expiry;
622	base->timers_pending = true;
623	base->next_expiry_recalc = false;
624	trigger_dyntick_cpu(base, timer);
625	}
626	}
627
628	static void internal_add_timer(struct timer_base *base, struct timer_list *timer)
629	{
630	unsigned long bucket_expiry;
631	unsigned int idx;
632
633	idx = calc_wheel_index(expires: timer->expires, clk: base->clk, bucket_expiry: &bucket_expiry);
634	enqueue_timer(base, timer, idx, bucket_expiry);
635	}
636
637	#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
638
639	static const struct debug_obj_descr timer_debug_descr;
640
641	struct timer_hint {
642	void (*function)(struct timer_list *t);
643	long offset;
644	};
645
646	#define TIMER_HINT(fn, container, timr, hintfn) \
647	{ \
648	.function = fn, \
649	.offset = offsetof(container, hintfn) - \
650	offsetof(container, timr) \
651	}
652
653	static const struct timer_hint timer_hints[] = {
654	TIMER_HINT(delayed_work_timer_fn,
655	struct delayed_work, timer, work.func),
656	TIMER_HINT(kthread_delayed_work_timer_fn,
657	struct kthread_delayed_work, timer, work.func),
658	};
659
660	static void *timer_debug_hint(void *addr)
661	{
662	struct timer_list *timer = addr;
663	int i;
664
665	for (i = 0; i < ARRAY_SIZE(timer_hints); i++) {
666	if (timer_hints[i].function == timer->function) {
667	void (**fn)(void) = addr + timer_hints[i].offset;
668
669	return *fn;
670	}
671	}
672
673	return timer->function;
674	}
675
676	static bool timer_is_static_object(void *addr)
677	{
678	struct timer_list *timer = addr;
679
680	return (timer->entry.pprev == NULL &&
681	timer->entry.next == TIMER_ENTRY_STATIC);
682	}
683
684	/*
685	* fixup_init is called when:
686	* - an active object is initialized
687	*/
688	static bool timer_fixup_init(void *addr, enum debug_obj_state state)
689	{
690	struct timer_list *timer = addr;
691
692	switch (state) {
693	case ODEBUG_STATE_ACTIVE:
694	del_timer_sync(timer);
695	debug_object_init(addr: timer, descr: &timer_debug_descr);
696	return true;
697	default:
698	return false;
699	}
700	}
701
702	/* Stub timer callback for improperly used timers. */
703	static void stub_timer(struct timer_list *unused)
704	{
705	WARN_ON(1);
706	}
707
708	/*
709	* fixup_activate is called when:
710	* - an active object is activated
711	* - an unknown non-static object is activated
712	*/
713	static bool timer_fixup_activate(void *addr, enum debug_obj_state state)
714	{
715	struct timer_list *timer = addr;
716
717	switch (state) {
718	case ODEBUG_STATE_NOTAVAILABLE:
719	timer_setup(timer, stub_timer, 0);
720	return true;
721
722	case ODEBUG_STATE_ACTIVE:
723	WARN_ON(1);
724	fallthrough;
725	default:
726	return false;
727	}
728	}
729
730	/*
731	* fixup_free is called when:
732	* - an active object is freed
733	*/
734	static bool timer_fixup_free(void *addr, enum debug_obj_state state)
735	{
736	struct timer_list *timer = addr;
737
738	switch (state) {
739	case ODEBUG_STATE_ACTIVE:
740	del_timer_sync(timer);
741	debug_object_free(addr: timer, descr: &timer_debug_descr);
742	return true;
743	default:
744	return false;
745	}
746	}
747
748	/*
749	* fixup_assert_init is called when:
750	* - an untracked/uninit-ed object is found
751	*/
752	static bool timer_fixup_assert_init(void *addr, enum debug_obj_state state)
753	{
754	struct timer_list *timer = addr;
755
756	switch (state) {
757	case ODEBUG_STATE_NOTAVAILABLE:
758	timer_setup(timer, stub_timer, 0);
759	return true;
760	default:
761	return false;
762	}
763	}
764
765	static const struct debug_obj_descr timer_debug_descr = {
766	.name = "timer_list",
767	.debug_hint = timer_debug_hint,
768	.is_static_object = timer_is_static_object,
769	.fixup_init = timer_fixup_init,
770	.fixup_activate = timer_fixup_activate,
771	.fixup_free = timer_fixup_free,
772	.fixup_assert_init = timer_fixup_assert_init,
773	};
774
775	static inline void debug_timer_init(struct timer_list *timer)
776	{
777	debug_object_init(addr: timer, descr: &timer_debug_descr);
778	}
779
780	static inline void debug_timer_activate(struct timer_list *timer)
781	{
782	debug_object_activate(addr: timer, descr: &timer_debug_descr);
783	}
784
785	static inline void debug_timer_deactivate(struct timer_list *timer)
786	{
787	debug_object_deactivate(addr: timer, descr: &timer_debug_descr);
788	}
789
790	static inline void debug_timer_assert_init(struct timer_list *timer)
791	{
792	debug_object_assert_init(addr: timer, descr: &timer_debug_descr);
793	}
794
795	static void do_init_timer(struct timer_list *timer,
796	void (*func)(struct timer_list *),
797	unsigned int flags,
798	const char *name, struct lock_class_key *key);
799
800	void init_timer_on_stack_key(struct timer_list *timer,
801	void (*func)(struct timer_list *),
802	unsigned int flags,
803	const char *name, struct lock_class_key *key)
804	{
805	debug_object_init_on_stack(addr: timer, descr: &timer_debug_descr);
806	do_init_timer(timer, func, flags, name, key);
807	}
808	EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
809
810	void destroy_timer_on_stack(struct timer_list *timer)
811	{
812	debug_object_free(addr: timer, descr: &timer_debug_descr);
813	}
814	EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
815
816	#else
817	static inline void debug_timer_init(struct timer_list *timer) { }
818	static inline void debug_timer_activate(struct timer_list *timer) { }
819	static inline void debug_timer_deactivate(struct timer_list *timer) { }
820	static inline void debug_timer_assert_init(struct timer_list *timer) { }
821	#endif
822
823	static inline void debug_init(struct timer_list *timer)
824	{
825	debug_timer_init(timer);
826	trace_timer_init(timer);
827	}
828
829	static inline void debug_deactivate(struct timer_list *timer)
830	{
831	debug_timer_deactivate(timer);
832	trace_timer_cancel(timer);
833	}
834
835	static inline void debug_assert_init(struct timer_list *timer)
836	{
837	debug_timer_assert_init(timer);
838	}
839
840	static void do_init_timer(struct timer_list *timer,
841	void (*func)(struct timer_list *),
842	unsigned int flags,
843	const char *name, struct lock_class_key *key)
844	{
845	timer->entry.pprev = NULL;
846	timer->function = func;
847	if (WARN_ON_ONCE(flags & ~TIMER_INIT_FLAGS))
848	flags &= TIMER_INIT_FLAGS;
849	timer->flags = flags | raw_smp_processor_id();
850	lockdep_init_map(lock: &timer->lockdep_map, name, key, subclass: 0);
851	}
852
853	/**
854	* init_timer_key - initialize a timer
855	* @timer: the timer to be initialized
856	* @func: timer callback function
857	* @flags: timer flags
858	* @name: name of the timer
859	* @key: lockdep class key of the fake lock used for tracking timer
860	* sync lock dependencies
861	*
862	* init_timer_key() must be done to a timer prior calling *any* of the
863	* other timer functions.
864	*/
865	void init_timer_key(struct timer_list *timer,
866	void (*func)(struct timer_list *), unsigned int flags,
867	const char *name, struct lock_class_key *key)
868	{
869	debug_init(timer);
870	do_init_timer(timer, func, flags, name, key);
871	}
872	EXPORT_SYMBOL(init_timer_key);
873
874	static inline void detach_timer(struct timer_list *timer, bool clear_pending)
875	{
876	struct hlist_node *entry = &timer->entry;
877
878	debug_deactivate(timer);
879
880	__hlist_del(n: entry);
881	if (clear_pending)
882	entry->pprev = NULL;
883	entry->next = LIST_POISON2;
884	}
885
886	static int detach_if_pending(struct timer_list *timer, struct timer_base *base,
887	bool clear_pending)
888	{
889	unsigned idx = timer_get_idx(timer);
890
891	if (!timer_pending(timer))
892	return 0;
893
894	if (hlist_is_singular_node(n: &timer->entry, h: base->vectors + idx)) {
895	__clear_bit(idx, base->pending_map);
896	base->next_expiry_recalc = true;
897	}
898
899	detach_timer(timer, clear_pending);
900	return 1;
901	}
902
903	static inline struct timer_base *get_timer_cpu_base(u32 tflags, u32 cpu)
904	{
905	struct timer_base *base = per_cpu_ptr(&timer_bases[BASE_STD], cpu);
906
907	/*
908	* If the timer is deferrable and NO_HZ_COMMON is set then we need
909	* to use the deferrable base.
910	*/
911	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
912	base = per_cpu_ptr(&timer_bases[BASE_DEF], cpu);
913	return base;
914	}
915
916	static inline struct timer_base *get_timer_this_cpu_base(u32 tflags)
917	{
918	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
919
920	/*
921	* If the timer is deferrable and NO_HZ_COMMON is set then we need
922	* to use the deferrable base.
923	*/
924	if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && (tflags & TIMER_DEFERRABLE))
925	base = this_cpu_ptr(&timer_bases[BASE_DEF]);
926	return base;
927	}
928
929	static inline struct timer_base *get_timer_base(u32 tflags)
930	{
931	return get_timer_cpu_base(tflags, cpu: tflags & TIMER_CPUMASK);
932	}
933
934	static inline struct timer_base *
935	get_target_base(struct timer_base *base, unsigned tflags)
936	{
937	#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
938	if (static_branch_likely(&timers_migration_enabled) &&
939	!(tflags & TIMER_PINNED))
940	return get_timer_cpu_base(tflags, cpu: get_nohz_timer_target());
941	#endif
942	return get_timer_this_cpu_base(tflags);
943	}
944
945	static inline void forward_timer_base(struct timer_base *base)
946	{
947	unsigned long jnow = READ_ONCE(jiffies);
948
949	/*
950	* No need to forward if we are close enough below jiffies.
951	* Also while executing timers, base->clk is 1 offset ahead
952	* of jiffies to avoid endless requeuing to current jiffies.
953	*/
954	if ((long)(jnow - base->clk) < 1)
955	return;
956
957	/*
958	* If the next expiry value is > jiffies, then we fast forward to
959	* jiffies otherwise we forward to the next expiry value.
960	*/
961	if (time_after(base->next_expiry, jnow)) {
962	base->clk = jnow;
963	} else {
964	if (WARN_ON_ONCE(time_before(base->next_expiry, base->clk)))
965	return;
966	base->clk = base->next_expiry;
967	}
968	}
969
970
971	/*
972	* We are using hashed locking: Holding per_cpu(timer_bases[x]).lock means
973	* that all timers which are tied to this base are locked, and the base itself
974	* is locked too.
975	*
976	* So __run_timers/migrate_timers can safely modify all timers which could
977	* be found in the base->vectors array.
978	*
979	* When a timer is migrating then the TIMER_MIGRATING flag is set and we need
980	* to wait until the migration is done.
981	*/
982	static struct timer_base *lock_timer_base(struct timer_list *timer,
983	unsigned long *flags)
984	__acquires(timer->base->lock)
985	{
986	for (;;) {
987	struct timer_base *base;
988	u32 tf;
989
990	/*
991	* We need to use READ_ONCE() here, otherwise the compiler
992	* might re-read @tf between the check for TIMER_MIGRATING
993	* and spin_lock().
994	*/
995	tf = READ_ONCE(timer->flags);
996
997	if (!(tf & TIMER_MIGRATING)) {
998	base = get_timer_base(tflags: tf);
999	raw_spin_lock_irqsave(&base->lock, *flags);
1000	if (timer->flags == tf)
1001	return base;
1002	raw_spin_unlock_irqrestore(&base->lock, *flags);
1003	}
1004	cpu_relax();
1005	}
1006	}
1007
1008	#define MOD_TIMER_PENDING_ONLY 0x01
1009	#define MOD_TIMER_REDUCE 0x02
1010	#define MOD_TIMER_NOTPENDING 0x04
1011
1012	static inline int
1013	__mod_timer(struct timer_list *timer, unsigned long expires, unsigned int options)
1014	{
1015	unsigned long clk = 0, flags, bucket_expiry;
1016	struct timer_base *base, *new_base;
1017	unsigned int idx = UINT_MAX;
1018	int ret = 0;
1019
1020	debug_assert_init(timer);
1021
1022	/*
1023	* This is a common optimization triggered by the networking code - if
1024	* the timer is re-modified to have the same timeout or ends up in the
1025	* same array bucket then just return:
1026	*/
1027	if (!(options & MOD_TIMER_NOTPENDING) && timer_pending(timer)) {
1028	/*
1029	* The downside of this optimization is that it can result in
1030	* larger granularity than you would get from adding a new
1031	* timer with this expiry.
1032	*/
1033	long diff = timer->expires - expires;
1034
1035	if (!diff)
1036	return 1;
1037	if (options & MOD_TIMER_REDUCE && diff <= 0)
1038	return 1;
1039
1040	/*
1041	* We lock timer base and calculate the bucket index right
1042	* here. If the timer ends up in the same bucket, then we
1043	* just update the expiry time and avoid the whole
1044	* dequeue/enqueue dance.
1045	*/
1046	base = lock_timer_base(timer, flags: &flags);
1047	/*
1048	* Has @timer been shutdown? This needs to be evaluated
1049	* while holding base lock to prevent a race against the
1050	* shutdown code.
1051	*/
1052	if (!timer->function)
1053	goto out_unlock;
1054
1055	forward_timer_base(base);
1056
1057	if (timer_pending(timer) && (options & MOD_TIMER_REDUCE) &&
1058	time_before_eq(timer->expires, expires)) {
1059	ret = 1;
1060	goto out_unlock;
1061	}
1062
1063	clk = base->clk;
1064	idx = calc_wheel_index(expires, clk, bucket_expiry: &bucket_expiry);
1065
1066	/*
1067	* Retrieve and compare the array index of the pending
1068	* timer. If it matches set the expiry to the new value so a
1069	* subsequent call will exit in the expires check above.
1070	*/
1071	if (idx == timer_get_idx(timer)) {
1072	if (!(options & MOD_TIMER_REDUCE))
1073	timer->expires = expires;
1074	else if (time_after(timer->expires, expires))
1075	timer->expires = expires;
1076	ret = 1;
1077	goto out_unlock;
1078	}
1079	} else {
1080	base = lock_timer_base(timer, flags: &flags);
1081	/*
1082	* Has @timer been shutdown? This needs to be evaluated
1083	* while holding base lock to prevent a race against the
1084	* shutdown code.
1085	*/
1086	if (!timer->function)
1087	goto out_unlock;
1088
1089	forward_timer_base(base);
1090	}
1091
1092	ret = detach_if_pending(timer, base, clear_pending: false);
1093	if (!ret && (options & MOD_TIMER_PENDING_ONLY))
1094	goto out_unlock;
1095
1096	new_base = get_target_base(base, tflags: timer->flags);
1097
1098	if (base != new_base) {
1099	/*
1100	* We are trying to schedule the timer on the new base.
1101	* However we can't change timer's base while it is running,
1102	* otherwise timer_delete_sync() can't detect that the timer's
1103	* handler yet has not finished. This also guarantees that the
1104	* timer is serialized wrt itself.
1105	*/
1106	if (likely(base->running_timer != timer)) {
1107	/* See the comment in lock_timer_base() */
1108	timer->flags |= TIMER_MIGRATING;
1109
1110	raw_spin_unlock(&base->lock);
1111	base = new_base;
1112	raw_spin_lock(&base->lock);
1113	WRITE_ONCE(timer->flags,
1114	(timer->flags & ~TIMER_BASEMASK) | base->cpu);
1115	forward_timer_base(base);
1116	}
1117	}
1118
1119	debug_timer_activate(timer);
1120
1121	timer->expires = expires;
1122	/*
1123	* If 'idx' was calculated above and the base time did not advance
1124	* between calculating 'idx' and possibly switching the base, only
1125	* enqueue_timer() is required. Otherwise we need to (re)calculate
1126	* the wheel index via internal_add_timer().
1127	*/
1128	if (idx != UINT_MAX && clk == base->clk)
1129	enqueue_timer(base, timer, idx, bucket_expiry);
1130	else
1131	internal_add_timer(base, timer);
1132
1133	out_unlock:
1134	raw_spin_unlock_irqrestore(&base->lock, flags);
1135
1136	return ret;
1137	}
1138
1139	/**
1140	* mod_timer_pending - Modify a pending timer's timeout
1141	* @timer: The pending timer to be modified
1142	* @expires: New absolute timeout in jiffies
1143	*
1144	* mod_timer_pending() is the same for pending timers as mod_timer(), but
1145	* will not activate inactive timers.
1146	*
1147	* If @timer->function == NULL then the start operation is silently
1148	* discarded.
1149	*
1150	* Return:
1151	* * %0 - The timer was inactive and not modified or was in
1152	* shutdown state and the operation was discarded
1153	* * %1 - The timer was active and requeued to expire at @expires
1154	*/
1155	int mod_timer_pending(struct timer_list *timer, unsigned long expires)
1156	{
1157	return __mod_timer(timer, expires, MOD_TIMER_PENDING_ONLY);
1158	}
1159	EXPORT_SYMBOL(mod_timer_pending);
1160
1161	/**
1162	* mod_timer - Modify a timer's timeout
1163	* @timer: The timer to be modified
1164	* @expires: New absolute timeout in jiffies
1165	*
1166	* mod_timer(timer, expires) is equivalent to:
1167	*
1168	* del_timer(timer); timer->expires = expires; add_timer(timer);
1169	*
1170	* mod_timer() is more efficient than the above open coded sequence. In
1171	* case that the timer is inactive, the del_timer() part is a NOP. The
1172	* timer is in any case activated with the new expiry time @expires.
1173	*
1174	* Note that if there are multiple unserialized concurrent users of the
1175	* same timer, then mod_timer() is the only safe way to modify the timeout,
1176	* since add_timer() cannot modify an already running timer.
1177	*
1178	* If @timer->function == NULL then the start operation is silently
1179	* discarded. In this case the return value is 0 and meaningless.
1180	*
1181	* Return:
1182	* * %0 - The timer was inactive and started or was in shutdown
1183	* state and the operation was discarded
1184	* * %1 - The timer was active and requeued to expire at @expires or
1185	* the timer was active and not modified because @expires did
1186	* not change the effective expiry time
1187	*/
1188	int mod_timer(struct timer_list *timer, unsigned long expires)
1189	{
1190	return __mod_timer(timer, expires, options: 0);
1191	}
1192	EXPORT_SYMBOL(mod_timer);
1193
1194	/**
1195	* timer_reduce - Modify a timer's timeout if it would reduce the timeout
1196	* @timer: The timer to be modified
1197	* @expires: New absolute timeout in jiffies
1198	*
1199	* timer_reduce() is very similar to mod_timer(), except that it will only
1200	* modify an enqueued timer if that would reduce the expiration time. If
1201	* @timer is not enqueued it starts the timer.
1202	*
1203	* If @timer->function == NULL then the start operation is silently
1204	* discarded.
1205	*
1206	* Return:
1207	* * %0 - The timer was inactive and started or was in shutdown
1208	* state and the operation was discarded
1209	* * %1 - The timer was active and requeued to expire at @expires or
1210	* the timer was active and not modified because @expires
1211	* did not change the effective expiry time such that the
1212	* timer would expire earlier than already scheduled
1213	*/
1214	int timer_reduce(struct timer_list *timer, unsigned long expires)
1215	{
1216	return __mod_timer(timer, expires, MOD_TIMER_REDUCE);
1217	}
1218	EXPORT_SYMBOL(timer_reduce);
1219
1220	/**
1221	* add_timer - Start a timer
1222	* @timer: The timer to be started
1223	*
1224	* Start @timer to expire at @timer->expires in the future. @timer->expires
1225	* is the absolute expiry time measured in 'jiffies'. When the timer expires
1226	* timer->function(timer) will be invoked from soft interrupt context.
1227	*
1228	* The @timer->expires and @timer->function fields must be set prior
1229	* to calling this function.
1230	*
1231	* If @timer->function == NULL then the start operation is silently
1232	* discarded.
1233	*
1234	* If @timer->expires is already in the past @timer will be queued to
1235	* expire at the next timer tick.
1236	*
1237	* This can only operate on an inactive timer. Attempts to invoke this on
1238	* an active timer are rejected with a warning.
1239	*/
1240	void add_timer(struct timer_list *timer)
1241	{
1242	if (WARN_ON_ONCE(timer_pending(timer)))
1243	return;
1244	__mod_timer(timer, expires: timer->expires, MOD_TIMER_NOTPENDING);
1245	}
1246	EXPORT_SYMBOL(add_timer);
1247
1248	/**
1249	* add_timer_on - Start a timer on a particular CPU
1250	* @timer: The timer to be started
1251	* @cpu: The CPU to start it on
1252	*
1253	* Same as add_timer() except that it starts the timer on the given CPU.
1254	*
1255	* See add_timer() for further details.
1256	*/
1257	void add_timer_on(struct timer_list *timer, int cpu)
1258	{
1259	struct timer_base *new_base, *base;
1260	unsigned long flags;
1261
1262	debug_assert_init(timer);
1263
1264	if (WARN_ON_ONCE(timer_pending(timer)))
1265	return;
1266
1267	new_base = get_timer_cpu_base(tflags: timer->flags, cpu);
1268
1269	/*
1270	* If @timer was on a different CPU, it should be migrated with the
1271	* old base locked to prevent other operations proceeding with the
1272	* wrong base locked. See lock_timer_base().
1273	*/
1274	base = lock_timer_base(timer, flags: &flags);
1275	/*
1276	* Has @timer been shutdown? This needs to be evaluated while
1277	* holding base lock to prevent a race against the shutdown code.
1278	*/
1279	if (!timer->function)
1280	goto out_unlock;
1281
1282	if (base != new_base) {
1283	timer->flags |= TIMER_MIGRATING;
1284
1285	raw_spin_unlock(&base->lock);
1286	base = new_base;
1287	raw_spin_lock(&base->lock);
1288	WRITE_ONCE(timer->flags,
1289	(timer->flags & ~TIMER_BASEMASK) | cpu);
1290	}
1291	forward_timer_base(base);
1292
1293	debug_timer_activate(timer);
1294	internal_add_timer(base, timer);
1295	out_unlock:
1296	raw_spin_unlock_irqrestore(&base->lock, flags);
1297	}
1298	EXPORT_SYMBOL_GPL(add_timer_on);
1299
1300	/**
1301	* __timer_delete - Internal function: Deactivate a timer
1302	* @timer: The timer to be deactivated
1303	* @shutdown: If true, this indicates that the timer is about to be
1304	* shutdown permanently.
1305	*
1306	* If @shutdown is true then @timer->function is set to NULL under the
1307	* timer base lock which prevents further rearming of the time. In that
1308	* case any attempt to rearm @timer after this function returns will be
1309	* silently ignored.
1310	*
1311	* Return:
1312	* * %0 - The timer was not pending
1313	* * %1 - The timer was pending and deactivated
1314	*/
1315	static int __timer_delete(struct timer_list *timer, bool shutdown)
1316	{
1317	struct timer_base *base;
1318	unsigned long flags;
1319	int ret = 0;
1320
1321	debug_assert_init(timer);
1322
1323	/*
1324	* If @shutdown is set then the lock has to be taken whether the
1325	* timer is pending or not to protect against a concurrent rearm
1326	* which might hit between the lockless pending check and the lock
1327	* aquisition. By taking the lock it is ensured that such a newly
1328	* enqueued timer is dequeued and cannot end up with
1329	* timer->function == NULL in the expiry code.
1330	*
1331	* If timer->function is currently executed, then this makes sure
1332	* that the callback cannot requeue the timer.
1333	*/
1334	if (timer_pending(timer) || shutdown) {
1335	base = lock_timer_base(timer, flags: &flags);
1336	ret = detach_if_pending(timer, base, clear_pending: true);
1337	if (shutdown)
1338	timer->function = NULL;
1339	raw_spin_unlock_irqrestore(&base->lock, flags);
1340	}
1341
1342	return ret;
1343	}
1344
1345	/**
1346	* timer_delete - Deactivate a timer
1347	* @timer: The timer to be deactivated
1348	*
1349	* The function only deactivates a pending timer, but contrary to
1350	* timer_delete_sync() it does not take into account whether the timer's
1351	* callback function is concurrently executed on a different CPU or not.
1352	* It neither prevents rearming of the timer. If @timer can be rearmed
1353	* concurrently then the return value of this function is meaningless.
1354	*
1355	* Return:
1356	* * %0 - The timer was not pending
1357	* * %1 - The timer was pending and deactivated
1358	*/
1359	int timer_delete(struct timer_list *timer)
1360	{
1361	return __timer_delete(timer, shutdown: false);
1362	}
1363	EXPORT_SYMBOL(timer_delete);
1364
1365	/**
1366	* timer_shutdown - Deactivate a timer and prevent rearming
1367	* @timer: The timer to be deactivated
1368	*
1369	* The function does not wait for an eventually running timer callback on a
1370	* different CPU but it prevents rearming of the timer. Any attempt to arm
1371	* @timer after this function returns will be silently ignored.
1372	*
1373	* This function is useful for teardown code and should only be used when
1374	* timer_shutdown_sync() cannot be invoked due to locking or context constraints.
1375	*
1376	* Return:
1377	* * %0 - The timer was not pending
1378	* * %1 - The timer was pending
1379	*/
1380	int timer_shutdown(struct timer_list *timer)
1381	{
1382	return __timer_delete(timer, shutdown: true);
1383	}
1384	EXPORT_SYMBOL_GPL(timer_shutdown);
1385
1386	/**
1387	* __try_to_del_timer_sync - Internal function: Try to deactivate a timer
1388	* @timer: Timer to deactivate
1389	* @shutdown: If true, this indicates that the timer is about to be
1390	* shutdown permanently.
1391	*
1392	* If @shutdown is true then @timer->function is set to NULL under the
1393	* timer base lock which prevents further rearming of the timer. Any
1394	* attempt to rearm @timer after this function returns will be silently
1395	* ignored.
1396	*
1397	* This function cannot guarantee that the timer cannot be rearmed
1398	* right after dropping the base lock if @shutdown is false. That
1399	* needs to be prevented by the calling code if necessary.
1400	*
1401	* Return:
1402	* * %0 - The timer was not pending
1403	* * %1 - The timer was pending and deactivated
1404	* * %-1 - The timer callback function is running on a different CPU
1405	*/
1406	static int __try_to_del_timer_sync(struct timer_list *timer, bool shutdown)
1407	{
1408	struct timer_base *base;
1409	unsigned long flags;
1410	int ret = -1;
1411
1412	debug_assert_init(timer);
1413
1414	base = lock_timer_base(timer, flags: &flags);
1415
1416	if (base->running_timer != timer)
1417	ret = detach_if_pending(timer, base, clear_pending: true);
1418	if (shutdown)
1419	timer->function = NULL;
1420
1421	raw_spin_unlock_irqrestore(&base->lock, flags);
1422
1423	return ret;
1424	}
1425
1426	/**
1427	* try_to_del_timer_sync - Try to deactivate a timer
1428	* @timer: Timer to deactivate
1429	*
1430	* This function tries to deactivate a timer. On success the timer is not
1431	* queued and the timer callback function is not running on any CPU.
1432	*
1433	* This function does not guarantee that the timer cannot be rearmed right
1434	* after dropping the base lock. That needs to be prevented by the calling
1435	* code if necessary.
1436	*
1437	* Return:
1438	* * %0 - The timer was not pending
1439	* * %1 - The timer was pending and deactivated
1440	* * %-1 - The timer callback function is running on a different CPU
1441	*/
1442	int try_to_del_timer_sync(struct timer_list *timer)
1443	{
1444	return __try_to_del_timer_sync(timer, shutdown: false);
1445	}
1446	EXPORT_SYMBOL(try_to_del_timer_sync);
1447
1448	#ifdef CONFIG_PREEMPT_RT
1449	static __init void timer_base_init_expiry_lock(struct timer_base *base)
1450	{
1451	spin_lock_init(&base->expiry_lock);
1452	}
1453
1454	static inline void timer_base_lock_expiry(struct timer_base *base)
1455	{
1456	spin_lock(&base->expiry_lock);
1457	}
1458
1459	static inline void timer_base_unlock_expiry(struct timer_base *base)
1460	{
1461	spin_unlock(&base->expiry_lock);
1462	}
1463
1464	/*
1465	* The counterpart to del_timer_wait_running().
1466	*
1467	* If there is a waiter for base->expiry_lock, then it was waiting for the
1468	* timer callback to finish. Drop expiry_lock and reacquire it. That allows
1469	* the waiter to acquire the lock and make progress.
1470	*/
1471	static void timer_sync_wait_running(struct timer_base *base)
1472	{
1473	if (atomic_read(&base->timer_waiters)) {
1474	raw_spin_unlock_irq(&base->lock);
1475	spin_unlock(&base->expiry_lock);
1476	spin_lock(&base->expiry_lock);
1477	raw_spin_lock_irq(&base->lock);
1478	}
1479	}
1480
1481	/*
1482	* This function is called on PREEMPT_RT kernels when the fast path
1483	* deletion of a timer failed because the timer callback function was
1484	* running.
1485	*
1486	* This prevents priority inversion, if the softirq thread on a remote CPU
1487	* got preempted, and it prevents a life lock when the task which tries to
1488	* delete a timer preempted the softirq thread running the timer callback
1489	* function.
1490	*/
1491	static void del_timer_wait_running(struct timer_list *timer)
1492	{
1493	u32 tf;
1494
1495	tf = READ_ONCE(timer->flags);
1496	if (!(tf & (TIMER_MIGRATING | TIMER_IRQSAFE))) {
1497	struct timer_base *base = get_timer_base(tf);
1498
1499	/*
1500	* Mark the base as contended and grab the expiry lock,
1501	* which is held by the softirq across the timer
1502	* callback. Drop the lock immediately so the softirq can
1503	* expire the next timer. In theory the timer could already
1504	* be running again, but that's more than unlikely and just
1505	* causes another wait loop.
1506	*/
1507	atomic_inc(&base->timer_waiters);
1508	spin_lock_bh(&base->expiry_lock);
1509	atomic_dec(&base->timer_waiters);
1510	spin_unlock_bh(&base->expiry_lock);
1511	}
1512	}
1513	#else
1514	static inline void timer_base_init_expiry_lock(struct timer_base *base) { }
1515	static inline void timer_base_lock_expiry(struct timer_base *base) { }
1516	static inline void timer_base_unlock_expiry(struct timer_base *base) { }
1517	static inline void timer_sync_wait_running(struct timer_base *base) { }
1518	static inline void del_timer_wait_running(struct timer_list *timer) { }
1519	#endif
1520
1521	/**
1522	* __timer_delete_sync - Internal function: Deactivate a timer and wait
1523	* for the handler to finish.
1524	* @timer: The timer to be deactivated
1525	* @shutdown: If true, @timer->function will be set to NULL under the
1526	* timer base lock which prevents rearming of @timer
1527	*
1528	* If @shutdown is not set the timer can be rearmed later. If the timer can
1529	* be rearmed concurrently, i.e. after dropping the base lock then the
1530	* return value is meaningless.
1531	*
1532	* If @shutdown is set then @timer->function is set to NULL under timer
1533	* base lock which prevents rearming of the timer. Any attempt to rearm
1534	* a shutdown timer is silently ignored.
1535	*
1536	* If the timer should be reused after shutdown it has to be initialized
1537	* again.
1538	*
1539	* Return:
1540	* * %0 - The timer was not pending
1541	* * %1 - The timer was pending and deactivated
1542	*/
1543	static int __timer_delete_sync(struct timer_list *timer, bool shutdown)
1544	{
1545	int ret;
1546
1547	#ifdef CONFIG_LOCKDEP
1548	unsigned long flags;
1549
1550	/*
1551	* If lockdep gives a backtrace here, please reference
1552	* the synchronization rules above.
1553	*/
1554	local_irq_save(flags);
1555	lock_map_acquire(&timer->lockdep_map);
1556	lock_map_release(&timer->lockdep_map);
1557	local_irq_restore(flags);
1558	#endif
1559	/*
1560	* don't use it in hardirq context, because it
1561	* could lead to deadlock.
1562	*/
1563	WARN_ON(in_hardirq() && !(timer->flags & TIMER_IRQSAFE));
1564
1565	/*
1566	* Must be able to sleep on PREEMPT_RT because of the slowpath in
1567	* del_timer_wait_running().
1568	*/
1569	if (IS_ENABLED(CONFIG_PREEMPT_RT) && !(timer->flags & TIMER_IRQSAFE))
1570	lockdep_assert_preemption_enabled();
1571
1572	do {
1573	ret = __try_to_del_timer_sync(timer, shutdown);
1574
1575	if (unlikely(ret < 0)) {
1576	del_timer_wait_running(timer);
1577	cpu_relax();
1578	}
1579	} while (ret < 0);
1580
1581	return ret;
1582	}
1583
1584	/**
1585	* timer_delete_sync - Deactivate a timer and wait for the handler to finish.
1586	* @timer: The timer to be deactivated
1587	*
1588	* Synchronization rules: Callers must prevent restarting of the timer,
1589	* otherwise this function is meaningless. It must not be called from
1590	* interrupt contexts unless the timer is an irqsafe one. The caller must
1591	* not hold locks which would prevent completion of the timer's callback
1592	* function. The timer's handler must not call add_timer_on(). Upon exit
1593	* the timer is not queued and the handler is not running on any CPU.
1594	*
1595	* For !irqsafe timers, the caller must not hold locks that are held in
1596	* interrupt context. Even if the lock has nothing to do with the timer in
1597	* question. Here's why::
1598	*
1599	* CPU0 CPU1
1600	* ---- ----
1601	* <SOFTIRQ>
1602	* call_timer_fn();
1603	* base->running_timer = mytimer;
1604	* spin_lock_irq(somelock);
1605	* <IRQ>
1606	* spin_lock(somelock);
1607	* timer_delete_sync(mytimer);
1608	* while (base->running_timer == mytimer);
1609	*
1610	* Now timer_delete_sync() will never return and never release somelock.
1611	* The interrupt on the other CPU is waiting to grab somelock but it has
1612	* interrupted the softirq that CPU0 is waiting to finish.
1613	*
1614	* This function cannot guarantee that the timer is not rearmed again by
1615	* some concurrent or preempting code, right after it dropped the base
1616	* lock. If there is the possibility of a concurrent rearm then the return
1617	* value of the function is meaningless.
1618	*
1619	* If such a guarantee is needed, e.g. for teardown situations then use
1620	* timer_shutdown_sync() instead.
1621	*
1622	* Return:
1623	* * %0 - The timer was not pending
1624	* * %1 - The timer was pending and deactivated
1625	*/
1626	int timer_delete_sync(struct timer_list *timer)
1627	{
1628	return __timer_delete_sync(timer, shutdown: false);
1629	}
1630	EXPORT_SYMBOL(timer_delete_sync);
1631
1632	/**
1633	* timer_shutdown_sync - Shutdown a timer and prevent rearming
1634	* @timer: The timer to be shutdown
1635	*
1636	* When the function returns it is guaranteed that:
1637	* - @timer is not queued
1638	* - The callback function of @timer is not running
1639	* - @timer cannot be enqueued again. Any attempt to rearm
1640	* @timer is silently ignored.
1641	*
1642	* See timer_delete_sync() for synchronization rules.
1643	*
1644	* This function is useful for final teardown of an infrastructure where
1645	* the timer is subject to a circular dependency problem.
1646	*
1647	* A common pattern for this is a timer and a workqueue where the timer can
1648	* schedule work and work can arm the timer. On shutdown the workqueue must
1649	* be destroyed and the timer must be prevented from rearming. Unless the
1650	* code has conditionals like 'if (mything->in_shutdown)' to prevent that
1651	* there is no way to get this correct with timer_delete_sync().
1652	*
1653	* timer_shutdown_sync() is solving the problem. The correct ordering of
1654	* calls in this case is:
1655	*
1656	* timer_shutdown_sync(&mything->timer);
1657	* workqueue_destroy(&mything->workqueue);
1658	*
1659	* After this 'mything' can be safely freed.
1660	*
1661	* This obviously implies that the timer is not required to be functional
1662	* for the rest of the shutdown operation.
1663	*
1664	* Return:
1665	* * %0 - The timer was not pending
1666	* * %1 - The timer was pending
1667	*/
1668	int timer_shutdown_sync(struct timer_list *timer)
1669	{
1670	return __timer_delete_sync(timer, shutdown: true);
1671	}
1672	EXPORT_SYMBOL_GPL(timer_shutdown_sync);
1673
1674	static void call_timer_fn(struct timer_list *timer,
1675	void (*fn)(struct timer_list *),
1676	unsigned long baseclk)
1677	{
1678	int count = preempt_count();
1679
1680	#ifdef CONFIG_LOCKDEP
1681	/*
1682	* It is permissible to free the timer from inside the
1683	* function that is called from it, this we need to take into
1684	* account for lockdep too. To avoid bogus "held lock freed"
1685	* warnings as well as problems when looking into
1686	* timer->lockdep_map, make a copy and use that here.
1687	*/
1688	struct lockdep_map lockdep_map;
1689
1690	lockdep_copy_map(to: &lockdep_map, from: &timer->lockdep_map);
1691	#endif
1692	/*
1693	* Couple the lock chain with the lock chain at
1694	* timer_delete_sync() by acquiring the lock_map around the fn()
1695	* call here and in timer_delete_sync().
1696	*/
1697	lock_map_acquire(&lockdep_map);
1698
1699	trace_timer_expire_entry(timer, baseclk);
1700	fn(timer);
1701	trace_timer_expire_exit(timer);
1702
1703	lock_map_release(&lockdep_map);
1704
1705	if (count != preempt_count()) {
1706	WARN_ONCE(1, "timer: %pS preempt leak: %08x -> %08x\n",
1707	fn, count, preempt_count());
1708	/*
1709	* Restore the preempt count. That gives us a decent
1710	* chance to survive and extract information. If the
1711	* callback kept a lock held, bad luck, but not worse
1712	* than the BUG() we had.
1713	*/
1714	preempt_count_set(pc: count);
1715	}
1716	}
1717
1718	static void expire_timers(struct timer_base *base, struct hlist_head *head)
1719	{
1720	/*
1721	* This value is required only for tracing. base->clk was
1722	* incremented directly before expire_timers was called. But expiry
1723	* is related to the old base->clk value.
1724	*/
1725	unsigned long baseclk = base->clk - 1;
1726
1727	while (!hlist_empty(h: head)) {
1728	struct timer_list *timer;
1729	void (*fn)(struct timer_list *);
1730
1731	timer = hlist_entry(head->first, struct timer_list, entry);
1732
1733	base->running_timer = timer;
1734	detach_timer(timer, clear_pending: true);
1735
1736	fn = timer->function;
1737
1738	if (WARN_ON_ONCE(!fn)) {
1739	/* Should never happen. Emphasis on should! */
1740	base->running_timer = NULL;
1741	continue;
1742	}
1743
1744	if (timer->flags & TIMER_IRQSAFE) {
1745	raw_spin_unlock(&base->lock);
1746	call_timer_fn(timer, fn, baseclk);
1747	raw_spin_lock(&base->lock);
1748	base->running_timer = NULL;
1749	} else {
1750	raw_spin_unlock_irq(&base->lock);
1751	call_timer_fn(timer, fn, baseclk);
1752	raw_spin_lock_irq(&base->lock);
1753	base->running_timer = NULL;
1754	timer_sync_wait_running(base);
1755	}
1756	}
1757	}
1758
1759	static int collect_expired_timers(struct timer_base *base,
1760	struct hlist_head *heads)
1761	{
1762	unsigned long clk = base->clk = base->next_expiry;
1763	struct hlist_head *vec;
1764	int i, levels = 0;
1765	unsigned int idx;
1766
1767	for (i = 0; i < LVL_DEPTH; i++) {
1768	idx = (clk & LVL_MASK) + i * LVL_SIZE;
1769
1770	if (__test_and_clear_bit(idx, base->pending_map)) {
1771	vec = base->vectors + idx;
1772	hlist_move_list(old: vec, new: heads++);
1773	levels++;
1774	}
1775	/* Is it time to look at the next level? */
1776	if (clk & LVL_CLK_MASK)
1777	break;
1778	/* Shift clock for the next level granularity */
1779	clk >>= LVL_CLK_SHIFT;
1780	}
1781	return levels;
1782	}
1783
1784	/*
1785	* Find the next pending bucket of a level. Search from level start (@offset)
1786	* + @clk upwards and if nothing there, search from start of the level
1787	* (@offset) up to @offset + clk.
1788	*/
1789	static int next_pending_bucket(struct timer_base *base, unsigned offset,
1790	unsigned clk)
1791	{
1792	unsigned pos, start = offset + clk;
1793	unsigned end = offset + LVL_SIZE;
1794
1795	pos = find_next_bit(addr: base->pending_map, size: end, offset: start);
1796	if (pos < end)
1797	return pos - start;
1798
1799	pos = find_next_bit(addr: base->pending_map, size: start, offset);
1800	return pos < start ? pos + LVL_SIZE - start : -1;
1801	}
1802
1803	/*
1804	* Search the first expiring timer in the various clock levels. Caller must
1805	* hold base->lock.
1806	*/
1807	static unsigned long __next_timer_interrupt(struct timer_base *base)
1808	{
1809	unsigned long clk, next, adj;
1810	unsigned lvl, offset = 0;
1811
1812	next = base->clk + NEXT_TIMER_MAX_DELTA;
1813	clk = base->clk;
1814	for (lvl = 0; lvl < LVL_DEPTH; lvl++, offset += LVL_SIZE) {
1815	int pos = next_pending_bucket(base, offset, clk: clk & LVL_MASK);
1816	unsigned long lvl_clk = clk & LVL_CLK_MASK;
1817
1818	if (pos >= 0) {
1819	unsigned long tmp = clk + (unsigned long) pos;
1820
1821	tmp <<= LVL_SHIFT(lvl);
1822	if (time_before(tmp, next))
1823	next = tmp;
1824
1825	/*
1826	* If the next expiration happens before we reach
1827	* the next level, no need to check further.
1828	*/
1829	if (pos <= ((LVL_CLK_DIV - lvl_clk) & LVL_CLK_MASK))
1830	break;
1831	}
1832	/*
1833	* Clock for the next level. If the current level clock lower
1834	* bits are zero, we look at the next level as is. If not we
1835	* need to advance it by one because that's going to be the
1836	* next expiring bucket in that level. base->clk is the next
1837	* expiring jiffie. So in case of:
1838	*
1839	* LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1840	* 0 0 0 0 0 0
1841	*
1842	* we have to look at all levels @index 0. With
1843	*
1844	* LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1845	* 0 0 0 0 0 2
1846	*
1847	* LVL0 has the next expiring bucket @index 2. The upper
1848	* levels have the next expiring bucket @index 1.
1849	*
1850	* In case that the propagation wraps the next level the same
1851	* rules apply:
1852	*
1853	* LVL5 LVL4 LVL3 LVL2 LVL1 LVL0
1854	* 0 0 0 0 F 2
1855	*
1856	* So after looking at LVL0 we get:
1857	*
1858	* LVL5 LVL4 LVL3 LVL2 LVL1
1859	* 0 0 0 1 0
1860	*
1861	* So no propagation from LVL1 to LVL2 because that happened
1862	* with the add already, but then we need to propagate further
1863	* from LVL2 to LVL3.
1864	*
1865	* So the simple check whether the lower bits of the current
1866	* level are 0 or not is sufficient for all cases.
1867	*/
1868	adj = lvl_clk ? 1 : 0;
1869	clk >>= LVL_CLK_SHIFT;
1870	clk += adj;
1871	}
1872
1873	base->next_expiry_recalc = false;
1874	base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA);
1875
1876	return next;
1877	}
1878
1879	#ifdef CONFIG_NO_HZ_COMMON
1880	/*
1881	* Check, if the next hrtimer event is before the next timer wheel
1882	* event:
1883	*/
1884	static u64 cmp_next_hrtimer_event(u64 basem, u64 expires)
1885	{
1886	u64 nextevt = hrtimer_get_next_event();
1887
1888	/*
1889	* If high resolution timers are enabled
1890	* hrtimer_get_next_event() returns KTIME_MAX.
1891	*/
1892	if (expires <= nextevt)
1893	return expires;
1894
1895	/*
1896	* If the next timer is already expired, return the tick base
1897	* time so the tick is fired immediately.
1898	*/
1899	if (nextevt <= basem)
1900	return basem;
1901
1902	/*
1903	* Round up to the next jiffie. High resolution timers are
1904	* off, so the hrtimers are expired in the tick and we need to
1905	* make sure that this tick really expires the timer to avoid
1906	* a ping pong of the nohz stop code.
1907	*
1908	* Use DIV_ROUND_UP_ULL to prevent gcc calling __divdi3
1909	*/
1910	return DIV_ROUND_UP_ULL(nextevt, TICK_NSEC) * TICK_NSEC;
1911	}
1912
1913	/**
1914	* get_next_timer_interrupt - return the time (clock mono) of the next timer
1915	* @basej: base time jiffies
1916	* @basem: base time clock monotonic
1917	*
1918	* Returns the tick aligned clock monotonic time of the next pending
1919	* timer or KTIME_MAX if no timer is pending.
1920	*/
1921	u64 get_next_timer_interrupt(unsigned long basej, u64 basem)
1922	{
1923	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1924	u64 expires = KTIME_MAX;
1925	unsigned long nextevt;
1926
1927	/*
1928	* Pretend that there is no timer pending if the cpu is offline.
1929	* Possible pending timers will be migrated later to an active cpu.
1930	*/
1931	if (cpu_is_offline(smp_processor_id()))
1932	return expires;
1933
1934	raw_spin_lock(&base->lock);
1935	if (base->next_expiry_recalc)
1936	base->next_expiry = __next_timer_interrupt(base);
1937	nextevt = base->next_expiry;
1938
1939	/*
1940	* We have a fresh next event. Check whether we can forward the
1941	* base. We can only do that when @basej is past base->clk
1942	* otherwise we might rewind base->clk.
1943	*/
1944	if (time_after(basej, base->clk)) {
1945	if (time_after(nextevt, basej))
1946	base->clk = basej;
1947	else if (time_after(nextevt, base->clk))
1948	base->clk = nextevt;
1949	}
1950
1951	if (time_before_eq(nextevt, basej)) {
1952	expires = basem;
1953	base->is_idle = false;
1954	} else {
1955	if (base->timers_pending)
1956	expires = basem + (u64)(nextevt - basej) * TICK_NSEC;
1957	/*
1958	* If we expect to sleep more than a tick, mark the base idle.
1959	* Also the tick is stopped so any added timer must forward
1960	* the base clk itself to keep granularity small. This idle
1961	* logic is only maintained for the BASE_STD base, deferrable
1962	* timers may still see large granularity skew (by design).
1963	*/
1964	if ((expires - basem) > TICK_NSEC)
1965	base->is_idle = true;
1966	}
1967	raw_spin_unlock(&base->lock);
1968
1969	return cmp_next_hrtimer_event(basem, expires);
1970	}
1971
1972	/**
1973	* timer_clear_idle - Clear the idle state of the timer base
1974	*
1975	* Called with interrupts disabled
1976	*/
1977	void timer_clear_idle(void)
1978	{
1979	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
1980
1981	/*
1982	* We do this unlocked. The worst outcome is a remote enqueue sending
1983	* a pointless IPI, but taking the lock would just make the window for
1984	* sending the IPI a few instructions smaller for the cost of taking
1985	* the lock in the exit from idle path.
1986	*/
1987	base->is_idle = false;
1988	}
1989	#endif
1990
1991	/**
1992	* __run_timers - run all expired timers (if any) on this CPU.
1993	* @base: the timer vector to be processed.
1994	*/
1995	static inline void __run_timers(struct timer_base *base)
1996	{
1997	struct hlist_head heads[LVL_DEPTH];
1998	int levels;
1999
2000	if (time_before(jiffies, base->next_expiry))
2001	return;
2002
2003	timer_base_lock_expiry(base);
2004	raw_spin_lock_irq(&base->lock);
2005
2006	while (time_after_eq(jiffies, base->clk) &&
2007	time_after_eq(jiffies, base->next_expiry)) {
2008	levels = collect_expired_timers(base, heads);
2009	/*
2010	* The two possible reasons for not finding any expired
2011	* timer at this clk are that all matching timers have been
2012	* dequeued or no timer has been queued since
2013	* base::next_expiry was set to base::clk +
2014	* NEXT_TIMER_MAX_DELTA.
2015	*/
2016	WARN_ON_ONCE(!levels && !base->next_expiry_recalc
2017	&& base->timers_pending);
2018	base->clk++;
2019	base->next_expiry = __next_timer_interrupt(base);
2020
2021	while (levels--)
2022	expire_timers(base, head: heads + levels);
2023	}
2024	raw_spin_unlock_irq(&base->lock);
2025	timer_base_unlock_expiry(base);
2026	}
2027
2028	/*
2029	* This function runs timers and the timer-tq in bottom half context.
2030	*/
2031	static __latent_entropy void run_timer_softirq(struct softirq_action *h)
2032	{
2033	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
2034
2035	__run_timers(base);
2036	if (IS_ENABLED(CONFIG_NO_HZ_COMMON))
2037	__run_timers(this_cpu_ptr(&timer_bases[BASE_DEF]));
2038	}
2039
2040	/*
2041	* Called by the local, per-CPU timer interrupt on SMP.
2042	*/
2043	static void run_local_timers(void)
2044	{
2045	struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]);
2046
2047	hrtimer_run_queues();
2048	/* Raise the softirq only if required. */
2049	if (time_before(jiffies, base->next_expiry)) {
2050	if (!IS_ENABLED(CONFIG_NO_HZ_COMMON))
2051	return;
2052	/* CPU is awake, so check the deferrable base. */
2053	base++;
2054	if (time_before(jiffies, base->next_expiry))
2055	return;
2056	}
2057	raise_softirq(nr: TIMER_SOFTIRQ);
2058	}
2059
2060	/*
2061	* Called from the timer interrupt handler to charge one tick to the current
2062	* process. user_tick is 1 if the tick is user time, 0 for system.
2063	*/
2064	void update_process_times(int user_tick)
2065	{
2066	struct task_struct *p = current;
2067
2068	/* Note: this timer irq context must be accounted for as well. */
2069	account_process_tick(p, user: user_tick);
2070	run_local_timers();
2071	rcu_sched_clock_irq(user: user_tick);
2072	#ifdef CONFIG_IRQ_WORK
2073	if (in_irq())
2074	irq_work_tick();
2075	#endif
2076	scheduler_tick();
2077	if (IS_ENABLED(CONFIG_POSIX_TIMERS))
2078	run_posix_cpu_timers();
2079	}
2080
2081	/*
2082	* Since schedule_timeout()'s timer is defined on the stack, it must store
2083	* the target task on the stack as well.
2084	*/
2085	struct process_timer {
2086	struct timer_list timer;
2087	struct task_struct *task;
2088	};
2089
2090	static void process_timeout(struct timer_list *t)
2091	{
2092	struct process_timer *timeout = from_timer(timeout, t, timer);
2093
2094	wake_up_process(tsk: timeout->task);
2095	}
2096
2097	/**
2098	* schedule_timeout - sleep until timeout
2099	* @timeout: timeout value in jiffies
2100	*
2101	* Make the current task sleep until @timeout jiffies have elapsed.
2102	* The function behavior depends on the current task state
2103	* (see also set_current_state() description):
2104	*
2105	* %TASK_RUNNING - the scheduler is called, but the task does not sleep
2106	* at all. That happens because sched_submit_work() does nothing for
2107	* tasks in %TASK_RUNNING state.
2108	*
2109	* %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
2110	* pass before the routine returns unless the current task is explicitly
2111	* woken up, (e.g. by wake_up_process()).
2112	*
2113	* %TASK_INTERRUPTIBLE - the routine may return early if a signal is
2114	* delivered to the current task or the current task is explicitly woken
2115	* up.
2116	*
2117	* The current task state is guaranteed to be %TASK_RUNNING when this
2118	* routine returns.
2119	*
2120	* Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
2121	* the CPU away without a bound on the timeout. In this case the return
2122	* value will be %MAX_SCHEDULE_TIMEOUT.
2123	*
2124	* Returns 0 when the timer has expired otherwise the remaining time in
2125	* jiffies will be returned. In all cases the return value is guaranteed
2126	* to be non-negative.
2127	*/
2128	signed long __sched schedule_timeout(signed long timeout)
2129	{
2130	struct process_timer timer;
2131	unsigned long expire;
2132
2133	switch (timeout)
2134	{
2135	case MAX_SCHEDULE_TIMEOUT:
2136	/*
2137	* These two special cases are useful to be comfortable
2138	* in the caller. Nothing more. We could take
2139	* MAX_SCHEDULE_TIMEOUT from one of the negative value
2140	* but I' d like to return a valid offset (>=0) to allow
2141	* the caller to do everything it want with the retval.
2142	*/
2143	schedule();
2144	goto out;
2145	default:
2146	/*
2147	* Another bit of PARANOID. Note that the retval will be
2148	* 0 since no piece of kernel is supposed to do a check
2149	* for a negative retval of schedule_timeout() (since it
2150	* should never happens anyway). You just have the printk()
2151	* that will tell you if something is gone wrong and where.
2152	*/
2153	if (timeout < 0) {
2154	printk(KERN_ERR "schedule_timeout: wrong timeout "
2155	"value %lx\n", timeout);
2156	dump_stack();
2157	__set_current_state(TASK_RUNNING);
2158	goto out;
2159	}
2160	}
2161
2162	expire = timeout + jiffies;
2163
2164	timer.task = current;
2165	timer_setup_on_stack(&timer.timer, process_timeout, 0);
2166	__mod_timer(timer: &timer.timer, expires: expire, MOD_TIMER_NOTPENDING);
2167	schedule();
2168	del_timer_sync(timer: &timer.timer);
2169
2170	/* Remove the timer from the object tracker */
2171	destroy_timer_on_stack(&timer.timer);
2172
2173	timeout = expire - jiffies;
2174
2175	out:
2176	return timeout < 0 ? 0 : timeout;
2177	}
2178	EXPORT_SYMBOL(schedule_timeout);
2179
2180	/*
2181	* We can use __set_current_state() here because schedule_timeout() calls
2182	* schedule() unconditionally.
2183	*/
2184	signed long __sched schedule_timeout_interruptible(signed long timeout)
2185	{
2186	__set_current_state(TASK_INTERRUPTIBLE);
2187	return schedule_timeout(timeout);
2188	}
2189	EXPORT_SYMBOL(schedule_timeout_interruptible);
2190
2191	signed long __sched schedule_timeout_killable(signed long timeout)
2192	{
2193	__set_current_state(TASK_KILLABLE);
2194	return schedule_timeout(timeout);
2195	}
2196	EXPORT_SYMBOL(schedule_timeout_killable);
2197
2198	signed long __sched schedule_timeout_uninterruptible(signed long timeout)
2199	{
2200	__set_current_state(TASK_UNINTERRUPTIBLE);
2201	return schedule_timeout(timeout);
2202	}
2203	EXPORT_SYMBOL(schedule_timeout_uninterruptible);
2204
2205	/*
2206	* Like schedule_timeout_uninterruptible(), except this task will not contribute
2207	* to load average.
2208	*/
2209	signed long __sched schedule_timeout_idle(signed long timeout)
2210	{
2211	__set_current_state(TASK_IDLE);
2212	return schedule_timeout(timeout);
2213	}
2214	EXPORT_SYMBOL(schedule_timeout_idle);
2215
2216	#ifdef CONFIG_HOTPLUG_CPU
2217	static void migrate_timer_list(struct timer_base *new_base, struct hlist_head *head)
2218	{
2219	struct timer_list *timer;
2220	int cpu = new_base->cpu;
2221
2222	while (!hlist_empty(h: head)) {
2223	timer = hlist_entry(head->first, struct timer_list, entry);
2224	detach_timer(timer, clear_pending: false);
2225	timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
2226	internal_add_timer(base: new_base, timer);
2227	}
2228	}
2229
2230	int timers_prepare_cpu(unsigned int cpu)
2231	{
2232	struct timer_base *base;
2233	int b;
2234
2235	for (b = 0; b < NR_BASES; b++) {
2236	base = per_cpu_ptr(&timer_bases[b], cpu);
2237	base->clk = jiffies;
2238	base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2239	base->next_expiry_recalc = false;
2240	base->timers_pending = false;
2241	base->is_idle = false;
2242	}
2243	return 0;
2244	}
2245
2246	int timers_dead_cpu(unsigned int cpu)
2247	{
2248	struct timer_base *old_base;
2249	struct timer_base *new_base;
2250	int b, i;
2251
2252	for (b = 0; b < NR_BASES; b++) {
2253	old_base = per_cpu_ptr(&timer_bases[b], cpu);
2254	new_base = get_cpu_ptr(&timer_bases[b]);
2255	/*
2256	* The caller is globally serialized and nobody else
2257	* takes two locks at once, deadlock is not possible.
2258	*/
2259	raw_spin_lock_irq(&new_base->lock);
2260	raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
2261
2262	/*
2263	* The current CPUs base clock might be stale. Update it
2264	* before moving the timers over.
2265	*/
2266	forward_timer_base(base: new_base);
2267
2268	WARN_ON_ONCE(old_base->running_timer);
2269	old_base->running_timer = NULL;
2270
2271	for (i = 0; i < WHEEL_SIZE; i++)
2272	migrate_timer_list(new_base, head: old_base->vectors + i);
2273
2274	raw_spin_unlock(&old_base->lock);
2275	raw_spin_unlock_irq(&new_base->lock);
2276	put_cpu_ptr(&timer_bases);
2277	}
2278	return 0;
2279	}
2280
2281	#endif /* CONFIG_HOTPLUG_CPU */
2282
2283	static void __init init_timer_cpu(int cpu)
2284	{
2285	struct timer_base *base;
2286	int i;
2287
2288	for (i = 0; i < NR_BASES; i++) {
2289	base = per_cpu_ptr(&timer_bases[i], cpu);
2290	base->cpu = cpu;
2291	raw_spin_lock_init(&base->lock);
2292	base->clk = jiffies;
2293	base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA;
2294	timer_base_init_expiry_lock(base);
2295	}
2296	}
2297
2298	static void __init init_timer_cpus(void)
2299	{
2300	int cpu;
2301
2302	for_each_possible_cpu(cpu)
2303	init_timer_cpu(cpu);
2304	}
2305
2306	void __init init_timers(void)
2307	{
2308	init_timer_cpus();
2309	posix_cputimers_init_work();
2310	open_softirq(nr: TIMER_SOFTIRQ, action: run_timer_softirq);
2311	}
2312
2313	/**
2314	* msleep - sleep safely even with waitqueue interruptions
2315	* @msecs: Time in milliseconds to sleep for
2316	*/
2317	void msleep(unsigned int msecs)
2318	{
2319	unsigned long timeout = msecs_to_jiffies(m: msecs) + 1;
2320
2321	while (timeout)
2322	timeout = schedule_timeout_uninterruptible(timeout);
2323	}
2324
2325	EXPORT_SYMBOL(msleep);
2326
2327	/**
2328	* msleep_interruptible - sleep waiting for signals
2329	* @msecs: Time in milliseconds to sleep for
2330	*/
2331	unsigned long msleep_interruptible(unsigned int msecs)
2332	{
2333	unsigned long timeout = msecs_to_jiffies(m: msecs) + 1;
2334
2335	while (timeout && !signal_pending(current))
2336	timeout = schedule_timeout_interruptible(timeout);
2337	return jiffies_to_msecs(j: timeout);
2338	}
2339
2340	EXPORT_SYMBOL(msleep_interruptible);
2341
2342	/**
2343	* usleep_range_state - Sleep for an approximate time in a given state
2344	* @min: Minimum time in usecs to sleep
2345	* @max: Maximum time in usecs to sleep
2346	* @state: State of the current task that will be while sleeping
2347	*
2348	* In non-atomic context where the exact wakeup time is flexible, use
2349	* usleep_range_state() instead of udelay(). The sleep improves responsiveness
2350	* by avoiding the CPU-hogging busy-wait of udelay(), and the range reduces
2351	* power usage by allowing hrtimers to take advantage of an already-
2352	* scheduled interrupt instead of scheduling a new one just for this sleep.
2353	*/
2354	void __sched usleep_range_state(unsigned long min, unsigned long max,
2355	unsigned int state)
2356	{
2357	ktime_t exp = ktime_add_us(kt: ktime_get(), usec: min);
2358	u64 delta = (u64)(max - min) * NSEC_PER_USEC;
2359
2360	for (;;) {
2361	__set_current_state(state);
2362	/* Do not return before the requested sleep time has elapsed */
2363	if (!schedule_hrtimeout_range(expires: &exp, delta, mode: HRTIMER_MODE_ABS))
2364	break;
2365	}
2366	}
2367	EXPORT_SYMBOL(usleep_range_state);
2368