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