linux/kernel/timer.c
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   1/*
   2 *  linux/kernel/timer.c
   3 *
   4 *  Kernel internal timers, basic process system calls
   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/slab.h>
  43
  44#include <asm/uaccess.h>
  45#include <asm/unistd.h>
  46#include <asm/div64.h>
  47#include <asm/timex.h>
  48#include <asm/io.h>
  49
  50#define CREATE_TRACE_POINTS
  51#include <trace/events/timer.h>
  52
  53u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
  54
  55EXPORT_SYMBOL(jiffies_64);
  56
  57/*
  58 * per-CPU timer vector definitions:
  59 */
  60#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
  61#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
  62#define TVN_SIZE (1 << TVN_BITS)
  63#define TVR_SIZE (1 << TVR_BITS)
  64#define TVN_MASK (TVN_SIZE - 1)
  65#define TVR_MASK (TVR_SIZE - 1)
  66
  67struct tvec {
  68        struct list_head vec[TVN_SIZE];
  69};
  70
  71struct tvec_root {
  72        struct list_head vec[TVR_SIZE];
  73};
  74
  75struct tvec_base {
  76        spinlock_t lock;
  77        struct timer_list *running_timer;
  78        unsigned long timer_jiffies;
  79        unsigned long next_timer;
  80        struct tvec_root tv1;
  81        struct tvec tv2;
  82        struct tvec tv3;
  83        struct tvec tv4;
  84        struct tvec tv5;
  85} ____cacheline_aligned;
  86
  87struct tvec_base boot_tvec_bases;
  88EXPORT_SYMBOL(boot_tvec_bases);
  89static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
  90
  91/* Functions below help us manage 'deferrable' flag */
  92static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
  93{
  94        return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);
  95}
  96
  97static inline struct tvec_base *tbase_get_base(struct tvec_base *base)
  98{
  99        return ((struct tvec_base *)((unsigned long)base & ~TBASE_DEFERRABLE_FLAG));
 100}
 101
 102static inline void timer_set_deferrable(struct timer_list *timer)
 103{
 104        timer->base = TBASE_MAKE_DEFERRED(timer->base);
 105}
 106
 107static inline void
 108timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
 109{
 110        timer->base = (struct tvec_base *)((unsigned long)(new_base) |
 111                                      tbase_get_deferrable(timer->base));
 112}
 113
 114static unsigned long round_jiffies_common(unsigned long j, int cpu,
 115                bool force_up)
 116{
 117        int rem;
 118        unsigned long original = j;
 119
 120        /*
 121         * We don't want all cpus firing their timers at once hitting the
 122         * same lock or cachelines, so we skew each extra cpu with an extra
 123         * 3 jiffies. This 3 jiffies came originally from the mm/ code which
 124         * already did this.
 125         * The skew is done by adding 3*cpunr, then round, then subtract this
 126         * extra offset again.
 127         */
 128        j += cpu * 3;
 129
 130        rem = j % HZ;
 131
 132        /*
 133         * If the target jiffie is just after a whole second (which can happen
 134         * due to delays of the timer irq, long irq off times etc etc) then
 135         * we should round down to the whole second, not up. Use 1/4th second
 136         * as cutoff for this rounding as an extreme upper bound for this.
 137         * But never round down if @force_up is set.
 138         */
 139        if (rem < HZ/4 && !force_up) /* round down */
 140                j = j - rem;
 141        else /* round up */
 142                j = j - rem + HZ;
 143
 144        /* now that we have rounded, subtract the extra skew again */
 145        j -= cpu * 3;
 146
 147        if (j <= jiffies) /* rounding ate our timeout entirely; */
 148                return original;
 149        return j;
 150}
 151
 152/**
 153 * __round_jiffies - function to round jiffies to a full second
 154 * @j: the time in (absolute) jiffies that should be rounded
 155 * @cpu: the processor number on which the timeout will happen
 156 *
 157 * __round_jiffies() rounds an absolute time in the future (in jiffies)
 158 * up or down to (approximately) full seconds. This is useful for timers
 159 * for which the exact time they fire does not matter too much, as long as
 160 * they fire approximately every X seconds.
 161 *
 162 * By rounding these timers to whole seconds, all such timers will fire
 163 * at the same time, rather than at various times spread out. The goal
 164 * of this is to have the CPU wake up less, which saves power.
 165 *
 166 * The exact rounding is skewed for each processor to avoid all
 167 * processors firing at the exact same time, which could lead
 168 * to lock contention or spurious cache line bouncing.
 169 *
 170 * The return value is the rounded version of the @j parameter.
 171 */
 172unsigned long __round_jiffies(unsigned long j, int cpu)
 173{
 174        return round_jiffies_common(j, cpu, false);
 175}
 176EXPORT_SYMBOL_GPL(__round_jiffies);
 177
 178/**
 179 * __round_jiffies_relative - function to round jiffies to a full second
 180 * @j: the time in (relative) jiffies that should be rounded
 181 * @cpu: the processor number on which the timeout will happen
 182 *
 183 * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
 184 * up or down to (approximately) full seconds. This is useful for timers
 185 * for which the exact time they fire does not matter too much, as long as
 186 * they fire approximately every X seconds.
 187 *
 188 * By rounding these timers to whole seconds, all such timers will fire
 189 * at the same time, rather than at various times spread out. The goal
 190 * of this is to have the CPU wake up less, which saves power.
 191 *
 192 * The exact rounding is skewed for each processor to avoid all
 193 * processors firing at the exact same time, which could lead
 194 * to lock contention or spurious cache line bouncing.
 195 *
 196 * The return value is the rounded version of the @j parameter.
 197 */
 198unsigned long __round_jiffies_relative(unsigned long j, int cpu)
 199{
 200        unsigned long j0 = jiffies;
 201
 202        /* Use j0 because jiffies might change while we run */
 203        return round_jiffies_common(j + j0, cpu, false) - j0;
 204}
 205EXPORT_SYMBOL_GPL(__round_jiffies_relative);
 206
 207/**
 208 * round_jiffies - function to round jiffies to a full second
 209 * @j: the time in (absolute) jiffies that should be rounded
 210 *
 211 * round_jiffies() rounds an absolute time in the future (in jiffies)
 212 * up or down to (approximately) full seconds. This is useful for timers
 213 * for which the exact time they fire does not matter too much, as long as
 214 * they fire approximately every X seconds.
 215 *
 216 * By rounding these timers to whole seconds, all such timers will fire
 217 * at the same time, rather than at various times spread out. The goal
 218 * of this is to have the CPU wake up less, which saves power.
 219 *
 220 * The return value is the rounded version of the @j parameter.
 221 */
 222unsigned long round_jiffies(unsigned long j)
 223{
 224        return round_jiffies_common(j, raw_smp_processor_id(), false);
 225}
 226EXPORT_SYMBOL_GPL(round_jiffies);
 227
 228/**
 229 * round_jiffies_relative - function to round jiffies to a full second
 230 * @j: the time in (relative) jiffies that should be rounded
 231 *
 232 * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
 233 * up or down to (approximately) full seconds. This is useful for timers
 234 * for which the exact time they fire does not matter too much, as long as
 235 * they fire approximately every X seconds.
 236 *
 237 * By rounding these timers to whole seconds, all such timers will fire
 238 * at the same time, rather than at various times spread out. The goal
 239 * of this is to have the CPU wake up less, which saves power.
 240 *
 241 * The return value is the rounded version of the @j parameter.
 242 */
 243unsigned long round_jiffies_relative(unsigned long j)
 244{
 245        return __round_jiffies_relative(j, raw_smp_processor_id());
 246}
 247EXPORT_SYMBOL_GPL(round_jiffies_relative);
 248
 249/**
 250 * __round_jiffies_up - function to round jiffies up to a full second
 251 * @j: the time in (absolute) jiffies that should be rounded
 252 * @cpu: the processor number on which the timeout will happen
 253 *
 254 * This is the same as __round_jiffies() except that it will never
 255 * round down.  This is useful for timeouts for which the exact time
 256 * of firing does not matter too much, as long as they don't fire too
 257 * early.
 258 */
 259unsigned long __round_jiffies_up(unsigned long j, int cpu)
 260{
 261        return round_jiffies_common(j, cpu, true);
 262}
 263EXPORT_SYMBOL_GPL(__round_jiffies_up);
 264
 265/**
 266 * __round_jiffies_up_relative - function to round jiffies up to a full second
 267 * @j: the time in (relative) jiffies that should be rounded
 268 * @cpu: the processor number on which the timeout will happen
 269 *
 270 * This is the same as __round_jiffies_relative() except that it will never
 271 * round down.  This is useful for timeouts for which the exact time
 272 * of firing does not matter too much, as long as they don't fire too
 273 * early.
 274 */
 275unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
 276{
 277        unsigned long j0 = jiffies;
 278
 279        /* Use j0 because jiffies might change while we run */
 280        return round_jiffies_common(j + j0, cpu, true) - j0;
 281}
 282EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
 283
 284/**
 285 * round_jiffies_up - function to round jiffies up to a full second
 286 * @j: the time in (absolute) jiffies that should be rounded
 287 *
 288 * This is the same as round_jiffies() except that it will never
 289 * round down.  This is useful for timeouts for which the exact time
 290 * of firing does not matter too much, as long as they don't fire too
 291 * early.
 292 */
 293unsigned long round_jiffies_up(unsigned long j)
 294{
 295        return round_jiffies_common(j, raw_smp_processor_id(), true);
 296}
 297EXPORT_SYMBOL_GPL(round_jiffies_up);
 298
 299/**
 300 * round_jiffies_up_relative - function to round jiffies up to a full second
 301 * @j: the time in (relative) jiffies that should be rounded
 302 *
 303 * This is the same as round_jiffies_relative() except that it will never
 304 * round down.  This is useful for timeouts for which the exact time
 305 * of firing does not matter too much, as long as they don't fire too
 306 * early.
 307 */
 308unsigned long round_jiffies_up_relative(unsigned long j)
 309{
 310        return __round_jiffies_up_relative(j, raw_smp_processor_id());
 311}
 312EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
 313
 314/**
 315 * set_timer_slack - set the allowed slack for a timer
 316 * @timer: the timer to be modified
 317 * @slack_hz: the amount of time (in jiffies) allowed for rounding
 318 *
 319 * Set the amount of time, in jiffies, that a certain timer has
 320 * in terms of slack. By setting this value, the timer subsystem
 321 * will schedule the actual timer somewhere between
 322 * the time mod_timer() asks for, and that time plus the slack.
 323 *
 324 * By setting the slack to -1, a percentage of the delay is used
 325 * instead.
 326 */
 327void set_timer_slack(struct timer_list *timer, int slack_hz)
 328{
 329        timer->slack = slack_hz;
 330}
 331EXPORT_SYMBOL_GPL(set_timer_slack);
 332
 333static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 334{
 335        unsigned long expires = timer->expires;
 336        unsigned long idx = expires - base->timer_jiffies;
 337        struct list_head *vec;
 338
 339        if (idx < TVR_SIZE) {
 340                int i = expires & TVR_MASK;
 341                vec = base->tv1.vec + i;
 342        } else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
 343                int i = (expires >> TVR_BITS) & TVN_MASK;
 344                vec = base->tv2.vec + i;
 345        } else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
 346                int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
 347                vec = base->tv3.vec + i;
 348        } else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
 349                int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
 350                vec = base->tv4.vec + i;
 351        } else if ((signed long) idx < 0) {
 352                /*
 353                 * Can happen if you add a timer with expires == jiffies,
 354                 * or you set a timer to go off in the past
 355                 */
 356                vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
 357        } else {
 358                int i;
 359                /* If the timeout is larger than 0xffffffff on 64-bit
 360                 * architectures then we use the maximum timeout:
 361                 */
 362                if (idx > 0xffffffffUL) {
 363                        idx = 0xffffffffUL;
 364                        expires = idx + base->timer_jiffies;
 365                }
 366                i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
 367                vec = base->tv5.vec + i;
 368        }
 369        /*
 370         * Timers are FIFO:
 371         */
 372        list_add_tail(&timer->entry, vec);
 373}
 374
 375#ifdef CONFIG_TIMER_STATS
 376void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
 377{
 378        if (timer->start_site)
 379                return;
 380
 381        timer->start_site = addr;
 382        memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
 383        timer->start_pid = current->pid;
 384}
 385
 386static void timer_stats_account_timer(struct timer_list *timer)
 387{
 388        unsigned int flag = 0;
 389
 390        if (likely(!timer->start_site))
 391                return;
 392        if (unlikely(tbase_get_deferrable(timer->base)))
 393                flag |= TIMER_STATS_FLAG_DEFERRABLE;
 394
 395        timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
 396                                 timer->function, timer->start_comm, flag);
 397}
 398
 399#else
 400static void timer_stats_account_timer(struct timer_list *timer) {}
 401#endif
 402
 403#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
 404
 405static struct debug_obj_descr timer_debug_descr;
 406
 407static void *timer_debug_hint(void *addr)
 408{
 409        return ((struct timer_list *) addr)->function;
 410}
 411
 412/*
 413 * fixup_init is called when:
 414 * - an active object is initialized
 415 */
 416static int timer_fixup_init(void *addr, enum debug_obj_state state)
 417{
 418        struct timer_list *timer = addr;
 419
 420        switch (state) {
 421        case ODEBUG_STATE_ACTIVE:
 422                del_timer_sync(timer);
 423                debug_object_init(timer, &timer_debug_descr);
 424                return 1;
 425        default:
 426                return 0;
 427        }
 428}
 429
 430/* Stub timer callback for improperly used timers. */
 431static void stub_timer(unsigned long data)
 432{
 433        WARN_ON(1);
 434}
 435
 436/*
 437 * fixup_activate is called when:
 438 * - an active object is activated
 439 * - an unknown object is activated (might be a statically initialized object)
 440 */
 441static int timer_fixup_activate(void *addr, enum debug_obj_state state)
 442{
 443        struct timer_list *timer = addr;
 444
 445        switch (state) {
 446
 447        case ODEBUG_STATE_NOTAVAILABLE:
 448                /*
 449                 * This is not really a fixup. The timer was
 450                 * statically initialized. We just make sure that it
 451                 * is tracked in the object tracker.
 452                 */
 453                if (timer->entry.next == NULL &&
 454                    timer->entry.prev == TIMER_ENTRY_STATIC) {
 455                        debug_object_init(timer, &timer_debug_descr);
 456                        debug_object_activate(timer, &timer_debug_descr);
 457                        return 0;
 458                } else {
 459                        setup_timer(timer, stub_timer, 0);
 460                        return 1;
 461                }
 462                return 0;
 463
 464        case ODEBUG_STATE_ACTIVE:
 465                WARN_ON(1);
 466
 467        default:
 468                return 0;
 469        }
 470}
 471
 472/*
 473 * fixup_free is called when:
 474 * - an active object is freed
 475 */
 476static int timer_fixup_free(void *addr, enum debug_obj_state state)
 477{
 478        struct timer_list *timer = addr;
 479
 480        switch (state) {
 481        case ODEBUG_STATE_ACTIVE:
 482                del_timer_sync(timer);
 483                debug_object_free(timer, &timer_debug_descr);
 484                return 1;
 485        default:
 486                return 0;
 487        }
 488}
 489
 490/*
 491 * fixup_assert_init is called when:
 492 * - an untracked/uninit-ed object is found
 493 */
 494static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
 495{
 496        struct timer_list *timer = addr;
 497
 498        switch (state) {
 499        case ODEBUG_STATE_NOTAVAILABLE:
 500                if (timer->entry.prev == TIMER_ENTRY_STATIC) {
 501                        /*
 502                         * This is not really a fixup. The timer was
 503                         * statically initialized. We just make sure that it
 504                         * is tracked in the object tracker.
 505                         */
 506                        debug_object_init(timer, &timer_debug_descr);
 507                        return 0;
 508                } else {
 509                        setup_timer(timer, stub_timer, 0);
 510                        return 1;
 511                }
 512        default:
 513                return 0;
 514        }
 515}
 516
 517static struct debug_obj_descr timer_debug_descr = {
 518        .name                   = "timer_list",
 519        .debug_hint             = timer_debug_hint,
 520        .fixup_init             = timer_fixup_init,
 521        .fixup_activate         = timer_fixup_activate,
 522        .fixup_free             = timer_fixup_free,
 523        .fixup_assert_init      = timer_fixup_assert_init,
 524};
 525
 526static inline void debug_timer_init(struct timer_list *timer)
 527{
 528        debug_object_init(timer, &timer_debug_descr);
 529}
 530
 531static inline void debug_timer_activate(struct timer_list *timer)
 532{
 533        debug_object_activate(timer, &timer_debug_descr);
 534}
 535
 536static inline void debug_timer_deactivate(struct timer_list *timer)
 537{
 538        debug_object_deactivate(timer, &timer_debug_descr);
 539}
 540
 541static inline void debug_timer_free(struct timer_list *timer)
 542{
 543        debug_object_free(timer, &timer_debug_descr);
 544}
 545
 546static inline void debug_timer_assert_init(struct timer_list *timer)
 547{
 548        debug_object_assert_init(timer, &timer_debug_descr);
 549}
 550
 551static void __init_timer(struct timer_list *timer,
 552                         const char *name,
 553                         struct lock_class_key *key);
 554
 555void init_timer_on_stack_key(struct timer_list *timer,
 556                             const char *name,
 557                             struct lock_class_key *key)
 558{
 559        debug_object_init_on_stack(timer, &timer_debug_descr);
 560        __init_timer(timer, name, key);
 561}
 562EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
 563
 564void destroy_timer_on_stack(struct timer_list *timer)
 565{
 566        debug_object_free(timer, &timer_debug_descr);
 567}
 568EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
 569
 570#else
 571static inline void debug_timer_init(struct timer_list *timer) { }
 572static inline void debug_timer_activate(struct timer_list *timer) { }
 573static inline void debug_timer_deactivate(struct timer_list *timer) { }
 574static inline void debug_timer_assert_init(struct timer_list *timer) { }
 575#endif
 576
 577static inline void debug_init(struct timer_list *timer)
 578{
 579        debug_timer_init(timer);
 580        trace_timer_init(timer);
 581}
 582
 583static inline void
 584debug_activate(struct timer_list *timer, unsigned long expires)
 585{
 586        debug_timer_activate(timer);
 587        trace_timer_start(timer, expires);
 588}
 589
 590static inline void debug_deactivate(struct timer_list *timer)
 591{
 592        debug_timer_deactivate(timer);
 593        trace_timer_cancel(timer);
 594}
 595
 596static inline void debug_assert_init(struct timer_list *timer)
 597{
 598        debug_timer_assert_init(timer);
 599}
 600
 601static void __init_timer(struct timer_list *timer,
 602                         const char *name,
 603                         struct lock_class_key *key)
 604{
 605        timer->entry.next = NULL;
 606        timer->base = __raw_get_cpu_var(tvec_bases);
 607        timer->slack = -1;
 608#ifdef CONFIG_TIMER_STATS
 609        timer->start_site = NULL;
 610        timer->start_pid = -1;
 611        memset(timer->start_comm, 0, TASK_COMM_LEN);
 612#endif
 613        lockdep_init_map(&timer->lockdep_map, name, key, 0);
 614}
 615
 616void setup_deferrable_timer_on_stack_key(struct timer_list *timer,
 617                                         const char *name,
 618                                         struct lock_class_key *key,
 619                                         void (*function)(unsigned long),
 620                                         unsigned long data)
 621{
 622        timer->function = function;
 623        timer->data = data;
 624        init_timer_on_stack_key(timer, name, key);
 625        timer_set_deferrable(timer);
 626}
 627EXPORT_SYMBOL_GPL(setup_deferrable_timer_on_stack_key);
 628
 629/**
 630 * init_timer_key - initialize a timer
 631 * @timer: the timer to be initialized
 632 * @name: name of the timer
 633 * @key: lockdep class key of the fake lock used for tracking timer
 634 *       sync lock dependencies
 635 *
 636 * init_timer_key() must be done to a timer prior calling *any* of the
 637 * other timer functions.
 638 */
 639void init_timer_key(struct timer_list *timer,
 640                    const char *name,
 641                    struct lock_class_key *key)
 642{
 643        debug_init(timer);
 644        __init_timer(timer, name, key);
 645}
 646EXPORT_SYMBOL(init_timer_key);
 647
 648void init_timer_deferrable_key(struct timer_list *timer,
 649                               const char *name,
 650                               struct lock_class_key *key)
 651{
 652        init_timer_key(timer, name, key);
 653        timer_set_deferrable(timer);
 654}
 655EXPORT_SYMBOL(init_timer_deferrable_key);
 656
 657static inline void detach_timer(struct timer_list *timer,
 658                                int clear_pending)
 659{
 660        struct list_head *entry = &timer->entry;
 661
 662        debug_deactivate(timer);
 663
 664        __list_del(entry->prev, entry->next);
 665        if (clear_pending)
 666                entry->next = NULL;
 667        entry->prev = LIST_POISON2;
 668}
 669
 670/*
 671 * We are using hashed locking: holding per_cpu(tvec_bases).lock
 672 * means that all timers which are tied to this base via timer->base are
 673 * locked, and the base itself is locked too.
 674 *
 675 * So __run_timers/migrate_timers can safely modify all timers which could
 676 * be found on ->tvX lists.
 677 *
 678 * When the timer's base is locked, and the timer removed from list, it is
 679 * possible to set timer->base = NULL and drop the lock: the timer remains
 680 * locked.
 681 */
 682static struct tvec_base *lock_timer_base(struct timer_list *timer,
 683                                        unsigned long *flags)
 684        __acquires(timer->base->lock)
 685{
 686        struct tvec_base *base;
 687
 688        for (;;) {
 689                struct tvec_base *prelock_base = timer->base;
 690                base = tbase_get_base(prelock_base);
 691                if (likely(base != NULL)) {
 692                        spin_lock_irqsave(&base->lock, *flags);
 693                        if (likely(prelock_base == timer->base))
 694                                return base;
 695                        /* The timer has migrated to another CPU */
 696                        spin_unlock_irqrestore(&base->lock, *flags);
 697                }
 698                cpu_relax();
 699        }
 700}
 701
 702static inline int
 703__mod_timer(struct timer_list *timer, unsigned long expires,
 704                                                bool pending_only, int pinned)
 705{
 706        struct tvec_base *base, *new_base;
 707        unsigned long flags;
 708        int ret = 0 , cpu;
 709
 710        timer_stats_timer_set_start_info(timer);
 711        BUG_ON(!timer->function);
 712
 713        base = lock_timer_base(timer, &flags);
 714
 715        if (timer_pending(timer)) {
 716                detach_timer(timer, 0);
 717                if (timer->expires == base->next_timer &&
 718                    !tbase_get_deferrable(timer->base))
 719                        base->next_timer = base->timer_jiffies;
 720                ret = 1;
 721        } else {
 722                if (pending_only)
 723                        goto out_unlock;
 724        }
 725
 726        debug_activate(timer, expires);
 727
 728        cpu = smp_processor_id();
 729
 730#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
 731        if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
 732                cpu = get_nohz_timer_target();
 733#endif
 734        new_base = per_cpu(tvec_bases, cpu);
 735
 736        if (base != new_base) {
 737                /*
 738                 * We are trying to schedule the timer on the local CPU.
 739                 * However we can't change timer's base while it is running,
 740                 * otherwise del_timer_sync() can't detect that the timer's
 741                 * handler yet has not finished. This also guarantees that
 742                 * the timer is serialized wrt itself.
 743                 */
 744                if (likely(base->running_timer != timer)) {
 745                        /* See the comment in lock_timer_base() */
 746                        timer_set_base(timer, NULL);
 747                        spin_unlock(&base->lock);
 748                        base = new_base;
 749                        spin_lock(&base->lock);
 750                        timer_set_base(timer, base);
 751                }
 752        }
 753
 754        timer->expires = expires;
 755        if (time_before(timer->expires, base->next_timer) &&
 756            !tbase_get_deferrable(timer->base))
 757                base->next_timer = timer->expires;
 758        internal_add_timer(base, timer);
 759
 760out_unlock:
 761        spin_unlock_irqrestore(&base->lock, flags);
 762
 763        return ret;
 764}
 765
 766/**
 767 * mod_timer_pending - modify a pending timer's timeout
 768 * @timer: the pending timer to be modified
 769 * @expires: new timeout in jiffies
 770 *
 771 * mod_timer_pending() is the same for pending timers as mod_timer(),
 772 * but will not re-activate and modify already deleted timers.
 773 *
 774 * It is useful for unserialized use of timers.
 775 */
 776int mod_timer_pending(struct timer_list *timer, unsigned long expires)
 777{
 778        return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
 779}
 780EXPORT_SYMBOL(mod_timer_pending);
 781
 782/*
 783 * Decide where to put the timer while taking the slack into account
 784 *
 785 * Algorithm:
 786 *   1) calculate the maximum (absolute) time
 787 *   2) calculate the highest bit where the expires and new max are different
 788 *   3) use this bit to make a mask
 789 *   4) use the bitmask to round down the maximum time, so that all last
 790 *      bits are zeros
 791 */
 792static inline
 793unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
 794{
 795        unsigned long expires_limit, mask;
 796        int bit;
 797
 798        if (timer->slack >= 0) {
 799                expires_limit = expires + timer->slack;
 800        } else {
 801                long delta = expires - jiffies;
 802
 803                if (delta < 256)
 804                        return expires;
 805
 806                expires_limit = expires + delta / 256;
 807        }
 808        mask = expires ^ expires_limit;
 809        if (mask == 0)
 810                return expires;
 811
 812        bit = find_last_bit(&mask, BITS_PER_LONG);
 813
 814        mask = (1 << bit) - 1;
 815
 816        expires_limit = expires_limit & ~(mask);
 817
 818        return expires_limit;
 819}
 820
 821/**
 822 * mod_timer - modify a timer's timeout
 823 * @timer: the timer to be modified
 824 * @expires: new timeout in jiffies
 825 *
 826 * mod_timer() is a more efficient way to update the expire field of an
 827 * active timer (if the timer is inactive it will be activated)
 828 *
 829 * mod_timer(timer, expires) is equivalent to:
 830 *
 831 *     del_timer(timer); timer->expires = expires; add_timer(timer);
 832 *
 833 * Note that if there are multiple unserialized concurrent users of the
 834 * same timer, then mod_timer() is the only safe way to modify the timeout,
 835 * since add_timer() cannot modify an already running timer.
 836 *
 837 * The function returns whether it has modified a pending timer or not.
 838 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
 839 * active timer returns 1.)
 840 */
 841int mod_timer(struct timer_list *timer, unsigned long expires)
 842{
 843        expires = apply_slack(timer, expires);
 844
 845        /*
 846         * This is a common optimization triggered by the
 847         * networking code - if the timer is re-modified
 848         * to be the same thing then just return:
 849         */
 850        if (timer_pending(timer) && timer->expires == expires)
 851                return 1;
 852
 853        return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
 854}
 855EXPORT_SYMBOL(mod_timer);
 856
 857/**
 858 * mod_timer_pinned - modify a timer's timeout
 859 * @timer: the timer to be modified
 860 * @expires: new timeout in jiffies
 861 *
 862 * mod_timer_pinned() is a way to update the expire field of an
 863 * active timer (if the timer is inactive it will be activated)
 864 * and to ensure that the timer is scheduled on the current CPU.
 865 *
 866 * Note that this does not prevent the timer from being migrated
 867 * when the current CPU goes offline.  If this is a problem for
 868 * you, use CPU-hotplug notifiers to handle it correctly, for
 869 * example, cancelling the timer when the corresponding CPU goes
 870 * offline.
 871 *
 872 * mod_timer_pinned(timer, expires) is equivalent to:
 873 *
 874 *     del_timer(timer); timer->expires = expires; add_timer(timer);
 875 */
 876int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
 877{
 878        if (timer->expires == expires && timer_pending(timer))
 879                return 1;
 880
 881        return __mod_timer(timer, expires, false, TIMER_PINNED);
 882}
 883EXPORT_SYMBOL(mod_timer_pinned);
 884
 885/**
 886 * add_timer - start a timer
 887 * @timer: the timer to be added
 888 *
 889 * The kernel will do a ->function(->data) callback from the
 890 * timer interrupt at the ->expires point in the future. The
 891 * current time is 'jiffies'.
 892 *
 893 * The timer's ->expires, ->function (and if the handler uses it, ->data)
 894 * fields must be set prior calling this function.
 895 *
 896 * Timers with an ->expires field in the past will be executed in the next
 897 * timer tick.
 898 */
 899void add_timer(struct timer_list *timer)
 900{
 901        BUG_ON(timer_pending(timer));
 902        mod_timer(timer, timer->expires);
 903}
 904EXPORT_SYMBOL(add_timer);
 905
 906/**
 907 * add_timer_on - start a timer on a particular CPU
 908 * @timer: the timer to be added
 909 * @cpu: the CPU to start it on
 910 *
 911 * This is not very scalable on SMP. Double adds are not possible.
 912 */
 913void add_timer_on(struct timer_list *timer, int cpu)
 914{
 915        struct tvec_base *base = per_cpu(tvec_bases, cpu);
 916        unsigned long flags;
 917
 918        timer_stats_timer_set_start_info(timer);
 919        BUG_ON(timer_pending(timer) || !timer->function);
 920        spin_lock_irqsave(&base->lock, flags);
 921        timer_set_base(timer, base);
 922        debug_activate(timer, timer->expires);
 923        if (time_before(timer->expires, base->next_timer) &&
 924            !tbase_get_deferrable(timer->base))
 925                base->next_timer = timer->expires;
 926        internal_add_timer(base, timer);
 927        /*
 928         * Check whether the other CPU is idle and needs to be
 929         * triggered to reevaluate the timer wheel when nohz is
 930         * active. We are protected against the other CPU fiddling
 931         * with the timer by holding the timer base lock. This also
 932         * makes sure that a CPU on the way to idle can not evaluate
 933         * the timer wheel.
 934         */
 935        wake_up_idle_cpu(cpu);
 936        spin_unlock_irqrestore(&base->lock, flags);
 937}
 938EXPORT_SYMBOL_GPL(add_timer_on);
 939
 940/**
 941 * del_timer - deactive a timer.
 942 * @timer: the timer to be deactivated
 943 *
 944 * del_timer() deactivates a timer - this works on both active and inactive
 945 * timers.
 946 *
 947 * The function returns whether it has deactivated a pending timer or not.
 948 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
 949 * active timer returns 1.)
 950 */
 951int del_timer(struct timer_list *timer)
 952{
 953        struct tvec_base *base;
 954        unsigned long flags;
 955        int ret = 0;
 956
 957        debug_assert_init(timer);
 958
 959        timer_stats_timer_clear_start_info(timer);
 960        if (timer_pending(timer)) {
 961                base = lock_timer_base(timer, &flags);
 962                if (timer_pending(timer)) {
 963                        detach_timer(timer, 1);
 964                        if (timer->expires == base->next_timer &&
 965                            !tbase_get_deferrable(timer->base))
 966                                base->next_timer = base->timer_jiffies;
 967                        ret = 1;
 968                }
 969                spin_unlock_irqrestore(&base->lock, flags);
 970        }
 971
 972        return ret;
 973}
 974EXPORT_SYMBOL(del_timer);
 975
 976/**
 977 * try_to_del_timer_sync - Try to deactivate a timer
 978 * @timer: timer do del
 979 *
 980 * This function tries to deactivate a timer. Upon successful (ret >= 0)
 981 * exit the timer is not queued and the handler is not running on any CPU.
 982 */
 983int try_to_del_timer_sync(struct timer_list *timer)
 984{
 985        struct tvec_base *base;
 986        unsigned long flags;
 987        int ret = -1;
 988
 989        debug_assert_init(timer);
 990
 991        base = lock_timer_base(timer, &flags);
 992
 993        if (base->running_timer == timer)
 994                goto out;
 995
 996        timer_stats_timer_clear_start_info(timer);
 997        ret = 0;
 998        if (timer_pending(timer)) {
 999                detach_timer(timer, 1);
1000                if (timer->expires == base->next_timer &&
1001                    !tbase_get_deferrable(timer->base))
1002                        base->next_timer = base->timer_jiffies;
1003                ret = 1;
1004        }
1005out:
1006        spin_unlock_irqrestore(&base->lock, flags);
1007
1008        return ret;
1009}
1010EXPORT_SYMBOL(try_to_del_timer_sync);
1011
1012#ifdef CONFIG_SMP
1013/**
1014 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1015 * @timer: the timer to be deactivated
1016 *
1017 * This function only differs from del_timer() on SMP: besides deactivating
1018 * the timer it also makes sure the handler has finished executing on other
1019 * CPUs.
1020 *
1021 * Synchronization rules: Callers must prevent restarting of the timer,
1022 * otherwise this function is meaningless. It must not be called from
1023 * interrupt contexts. The caller must not hold locks which would prevent
1024 * completion of the timer's handler. The timer's handler must not call
1025 * add_timer_on(). Upon exit the timer is not queued and the handler is
1026 * not running on any CPU.
1027 *
1028 * Note: You must not hold locks that are held in interrupt context
1029 *   while calling this function. Even if the lock has nothing to do
1030 *   with the timer in question.  Here's why:
1031 *
1032 *    CPU0                             CPU1
1033 *    ----                             ----
1034 *                                   <SOFTIRQ>
1035 *                                   call_timer_fn();
1036 *                                     base->running_timer = mytimer;
1037 *  spin_lock_irq(somelock);
1038 *                                     <IRQ>
1039 *                                        spin_lock(somelock);
1040 *  del_timer_sync(mytimer);
1041 *   while (base->running_timer == mytimer);
1042 *
1043 * Now del_timer_sync() will never return and never release somelock.
1044 * The interrupt on the other CPU is waiting to grab somelock but
1045 * it has interrupted the softirq that CPU0 is waiting to finish.
1046 *
1047 * The function returns whether it has deactivated a pending timer or not.
1048 */
1049int del_timer_sync(struct timer_list *timer)
1050{
1051#ifdef CONFIG_LOCKDEP
1052        unsigned long flags;
1053
1054        /*
1055         * If lockdep gives a backtrace here, please reference
1056         * the synchronization rules above.
1057         */
1058        local_irq_save(flags);
1059        lock_map_acquire(&timer->lockdep_map);
1060        lock_map_release(&timer->lockdep_map);
1061        local_irq_restore(flags);
1062#endif
1063        /*
1064         * don't use it in hardirq context, because it
1065         * could lead to deadlock.
1066         */
1067        WARN_ON(in_irq());
1068        for (;;) {
1069                int ret = try_to_del_timer_sync(timer);
1070                if (ret >= 0)
1071                        return ret;
1072                cpu_relax();
1073        }
1074}
1075EXPORT_SYMBOL(del_timer_sync);
1076#endif
1077
1078static int cascade(struct tvec_base *base, struct tvec *tv, int index)
1079{
1080        /* cascade all the timers from tv up one level */
1081        struct timer_list *timer, *tmp;
1082        struct list_head tv_list;
1083
1084        list_replace_init(tv->vec + index, &tv_list);
1085
1086        /*
1087         * We are removing _all_ timers from the list, so we
1088         * don't have to detach them individually.
1089         */
1090        list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
1091                BUG_ON(tbase_get_base(timer->base) != base);
1092                internal_add_timer(base, timer);
1093        }
1094
1095        return index;
1096}
1097
1098static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
1099                          unsigned long data)
1100{
1101        int preempt_count = preempt_count();
1102
1103#ifdef CONFIG_LOCKDEP
1104        /*
1105         * It is permissible to free the timer from inside the
1106         * function that is called from it, this we need to take into
1107         * account for lockdep too. To avoid bogus "held lock freed"
1108         * warnings as well as problems when looking into
1109         * timer->lockdep_map, make a copy and use that here.
1110         */
1111        struct lockdep_map lockdep_map;
1112
1113        lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1114#endif
1115        /*
1116         * Couple the lock chain with the lock chain at
1117         * del_timer_sync() by acquiring the lock_map around the fn()
1118         * call here and in del_timer_sync().
1119         */
1120        lock_map_acquire(&lockdep_map);
1121
1122        trace_timer_expire_entry(timer);
1123        fn(data);
1124        trace_timer_expire_exit(timer);
1125
1126        lock_map_release(&lockdep_map);
1127
1128        if (preempt_count != preempt_count()) {
1129                WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
1130                          fn, preempt_count, preempt_count());
1131                /*
1132                 * Restore the preempt count. That gives us a decent
1133                 * chance to survive and extract information. If the
1134                 * callback kept a lock held, bad luck, but not worse
1135                 * than the BUG() we had.
1136                 */
1137                preempt_count() = preempt_count;
1138        }
1139}
1140
1141#define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
1142
1143/**
1144 * __run_timers - run all expired timers (if any) on this CPU.
1145 * @base: the timer vector to be processed.
1146 *
1147 * This function cascades all vectors and executes all expired timer
1148 * vectors.
1149 */
1150static inline void __run_timers(struct tvec_base *base)
1151{
1152        struct timer_list *timer;
1153
1154        spin_lock_irq(&base->lock);
1155        while (time_after_eq(jiffies, base->timer_jiffies)) {
1156                struct list_head work_list;
1157                struct list_head *head = &work_list;
1158                int index = base->timer_jiffies & TVR_MASK;
1159
1160                /*
1161                 * Cascade timers:
1162                 */
1163                if (!index &&
1164                        (!cascade(base, &base->tv2, INDEX(0))) &&
1165                                (!cascade(base, &base->tv3, INDEX(1))) &&
1166                                        !cascade(base, &base->tv4, INDEX(2)))
1167                        cascade(base, &base->tv5, INDEX(3));
1168                ++base->timer_jiffies;
1169                list_replace_init(base->tv1.vec + index, &work_list);
1170                while (!list_empty(head)) {
1171                        void (*fn)(unsigned long);
1172                        unsigned long data;
1173
1174                        timer = list_first_entry(head, struct timer_list,entry);
1175                        fn = timer->function;
1176                        data = timer->data;
1177
1178                        timer_stats_account_timer(timer);
1179
1180                        base->running_timer = timer;
1181                        detach_timer(timer, 1);
1182
1183                        spin_unlock_irq(&base->lock);
1184                        call_timer_fn(timer, fn, data);
1185                        spin_lock_irq(&base->lock);
1186                }
1187        }
1188        base->running_timer = NULL;
1189        spin_unlock_irq(&base->lock);
1190}
1191
1192#ifdef CONFIG_NO_HZ
1193/*
1194 * Find out when the next timer event is due to happen. This
1195 * is used on S/390 to stop all activity when a CPU is idle.
1196 * This function needs to be called with interrupts disabled.
1197 */
1198static unsigned long __next_timer_interrupt(struct tvec_base *base)
1199{
1200        unsigned long timer_jiffies = base->timer_jiffies;
1201        unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;
1202        int index, slot, array, found = 0;
1203        struct timer_list *nte;
1204        struct tvec *varray[4];
1205
1206        /* Look for timer events in tv1. */
1207        index = slot = timer_jiffies & TVR_MASK;
1208        do {
1209                list_for_each_entry(nte, base->tv1.vec + slot, entry) {
1210                        if (tbase_get_deferrable(nte->base))
1211                                continue;
1212
1213                        found = 1;
1214                        expires = nte->expires;
1215                        /* Look at the cascade bucket(s)? */
1216                        if (!index || slot < index)
1217                                goto cascade;
1218                        return expires;
1219                }
1220                slot = (slot + 1) & TVR_MASK;
1221        } while (slot != index);
1222
1223cascade:
1224        /* Calculate the next cascade event */
1225        if (index)
1226                timer_jiffies += TVR_SIZE - index;
1227        timer_jiffies >>= TVR_BITS;
1228
1229        /* Check tv2-tv5. */
1230        varray[0] = &base->tv2;
1231        varray[1] = &base->tv3;
1232        varray[2] = &base->tv4;
1233        varray[3] = &base->tv5;
1234
1235        for (array = 0; array < 4; array++) {
1236                struct tvec *varp = varray[array];
1237
1238                index = slot = timer_jiffies & TVN_MASK;
1239                do {
1240                        list_for_each_entry(nte, varp->vec + slot, entry) {
1241                                if (tbase_get_deferrable(nte->base))
1242                                        continue;
1243
1244                                found = 1;
1245                                if (time_before(nte->expires, expires))
1246                                        expires = nte->expires;
1247                        }
1248                        /*
1249                         * Do we still search for the first timer or are
1250                         * we looking up the cascade buckets ?
1251                         */
1252                        if (found) {
1253                                /* Look at the cascade bucket(s)? */
1254                                if (!index || slot < index)
1255                                        break;
1256                                return expires;
1257                        }
1258                        slot = (slot + 1) & TVN_MASK;
1259                } while (slot != index);
1260
1261                if (index)
1262                        timer_jiffies += TVN_SIZE - index;
1263                timer_jiffies >>= TVN_BITS;
1264        }
1265        return expires;
1266}
1267
1268/*
1269 * Check, if the next hrtimer event is before the next timer wheel
1270 * event:
1271 */
1272static unsigned long cmp_next_hrtimer_event(unsigned long now,
1273                                            unsigned long expires)
1274{
1275        ktime_t hr_delta = hrtimer_get_next_event();
1276        struct timespec tsdelta;
1277        unsigned long delta;
1278
1279        if (hr_delta.tv64 == KTIME_MAX)
1280                return expires;
1281
1282        /*
1283         * Expired timer available, let it expire in the next tick
1284         */
1285        if (hr_delta.tv64 <= 0)
1286                return now + 1;
1287
1288        tsdelta = ktime_to_timespec(hr_delta);
1289        delta = timespec_to_jiffies(&tsdelta);
1290
1291        /*
1292         * Limit the delta to the max value, which is checked in
1293         * tick_nohz_stop_sched_tick():
1294         */
1295        if (delta > NEXT_TIMER_MAX_DELTA)
1296                delta = NEXT_TIMER_MAX_DELTA;
1297
1298        /*
1299         * Take rounding errors in to account and make sure, that it
1300         * expires in the next tick. Otherwise we go into an endless
1301         * ping pong due to tick_nohz_stop_sched_tick() retriggering
1302         * the timer softirq
1303         */
1304        if (delta < 1)
1305                delta = 1;
1306        now += delta;
1307        if (time_before(now, expires))
1308                return now;
1309        return expires;
1310}
1311
1312/**
1313 * get_next_timer_interrupt - return the jiffy of the next pending timer
1314 * @now: current time (in jiffies)
1315 */
1316unsigned long get_next_timer_interrupt(unsigned long now)
1317{
1318        struct tvec_base *base = __this_cpu_read(tvec_bases);
1319        unsigned long expires;
1320
1321        /*
1322         * Pretend that there is no timer pending if the cpu is offline.
1323         * Possible pending timers will be migrated later to an active cpu.
1324         */
1325        if (cpu_is_offline(smp_processor_id()))
1326                return now + NEXT_TIMER_MAX_DELTA;
1327        spin_lock(&base->lock);
1328        if (time_before_eq(base->next_timer, base->timer_jiffies))
1329                base->next_timer = __next_timer_interrupt(base);
1330        expires = base->next_timer;
1331        spin_unlock(&base->lock);
1332
1333        if (time_before_eq(expires, now))
1334                return now;
1335
1336        return cmp_next_hrtimer_event(now, expires);
1337}
1338#endif
1339
1340/*
1341 * Called from the timer interrupt handler to charge one tick to the current
1342 * process.  user_tick is 1 if the tick is user time, 0 for system.
1343 */
1344void update_process_times(int user_tick)
1345{
1346        struct task_struct *p = current;
1347        int cpu = smp_processor_id();
1348
1349        /* Note: this timer irq context must be accounted for as well. */
1350        account_process_tick(p, user_tick);
1351        run_local_timers();
1352        rcu_check_callbacks(cpu, user_tick);
1353        printk_tick();
1354#ifdef CONFIG_IRQ_WORK
1355        if (in_irq())
1356                irq_work_run();
1357#endif
1358        scheduler_tick();
1359        run_posix_cpu_timers(p);
1360}
1361
1362/*
1363 * This function runs timers and the timer-tq in bottom half context.
1364 */
1365static void run_timer_softirq(struct softirq_action *h)
1366{
1367        struct tvec_base *base = __this_cpu_read(tvec_bases);
1368
1369        hrtimer_run_pending();
1370
1371        if (time_after_eq(jiffies, base->timer_jiffies))
1372                __run_timers(base);
1373}
1374
1375/*
1376 * Called by the local, per-CPU timer interrupt on SMP.
1377 */
1378void run_local_timers(void)
1379{
1380        hrtimer_run_queues();
1381        raise_softirq(TIMER_SOFTIRQ);
1382}
1383
1384#ifdef __ARCH_WANT_SYS_ALARM
1385
1386/*
1387 * For backwards compatibility?  This can be done in libc so Alpha
1388 * and all newer ports shouldn't need it.
1389 */
1390SYSCALL_DEFINE1(alarm, unsigned int, seconds)
1391{
1392        return alarm_setitimer(seconds);
1393}
1394
1395#endif
1396
1397#ifndef __alpha__
1398
1399/*
1400 * The Alpha uses getxpid, getxuid, and getxgid instead.  Maybe this
1401 * should be moved into arch/i386 instead?
1402 */
1403
1404/**
1405 * sys_getpid - return the thread group id of the current process
1406 *
1407 * Note, despite the name, this returns the tgid not the pid.  The tgid and
1408 * the pid are identical unless CLONE_THREAD was specified on clone() in
1409 * which case the tgid is the same in all threads of the same group.
1410 *
1411 * This is SMP safe as current->tgid does not change.
1412 */
1413SYSCALL_DEFINE0(getpid)
1414{
1415        return task_tgid_vnr(current);
1416}
1417
1418/*
1419 * Accessing ->real_parent is not SMP-safe, it could
1420 * change from under us. However, we can use a stale
1421 * value of ->real_parent under rcu_read_lock(), see
1422 * release_task()->call_rcu(delayed_put_task_struct).
1423 */
1424SYSCALL_DEFINE0(getppid)
1425{
1426        int pid;
1427
1428        rcu_read_lock();
1429        pid = task_tgid_vnr(rcu_dereference(current->real_parent));
1430        rcu_read_unlock();
1431
1432        return pid;
1433}
1434
1435SYSCALL_DEFINE0(getuid)
1436{
1437        /* Only we change this so SMP safe */
1438        return from_kuid_munged(current_user_ns(), current_uid());
1439}
1440
1441SYSCALL_DEFINE0(geteuid)
1442{
1443        /* Only we change this so SMP safe */
1444        return from_kuid_munged(current_user_ns(), current_euid());
1445}
1446
1447SYSCALL_DEFINE0(getgid)
1448{
1449        /* Only we change this so SMP safe */
1450        return from_kgid_munged(current_user_ns(), current_gid());
1451}
1452
1453SYSCALL_DEFINE0(getegid)
1454{
1455        /* Only we change this so SMP safe */
1456        return from_kgid_munged(current_user_ns(), current_egid());
1457}
1458
1459#endif
1460
1461static void process_timeout(unsigned long __data)
1462{
1463        wake_up_process((struct task_struct *)__data);
1464}
1465
1466/**
1467 * schedule_timeout - sleep until timeout
1468 * @timeout: timeout value in jiffies
1469 *
1470 * Make the current task sleep until @timeout jiffies have
1471 * elapsed. The routine will return immediately unless
1472 * the current task state has been set (see set_current_state()).
1473 *
1474 * You can set the task state as follows -
1475 *
1476 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1477 * pass before the routine returns. The routine will return 0
1478 *
1479 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1480 * delivered to the current task. In this case the remaining time
1481 * in jiffies will be returned, or 0 if the timer expired in time
1482 *
1483 * The current task state is guaranteed to be TASK_RUNNING when this
1484 * routine returns.
1485 *
1486 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1487 * the CPU away without a bound on the timeout. In this case the return
1488 * value will be %MAX_SCHEDULE_TIMEOUT.
1489 *
1490 * In all cases the return value is guaranteed to be non-negative.
1491 */
1492signed long __sched schedule_timeout(signed long timeout)
1493{
1494        struct timer_list timer;
1495        unsigned long expire;
1496
1497        switch (timeout)
1498        {
1499        case MAX_SCHEDULE_TIMEOUT:
1500                /*
1501                 * These two special cases are useful to be comfortable
1502                 * in the caller. Nothing more. We could take
1503                 * MAX_SCHEDULE_TIMEOUT from one of the negative value
1504                 * but I' d like to return a valid offset (>=0) to allow
1505                 * the caller to do everything it want with the retval.
1506                 */
1507                schedule();
1508                goto out;
1509        default:
1510                /*
1511                 * Another bit of PARANOID. Note that the retval will be
1512                 * 0 since no piece of kernel is supposed to do a check
1513                 * for a negative retval of schedule_timeout() (since it
1514                 * should never happens anyway). You just have the printk()
1515                 * that will tell you if something is gone wrong and where.
1516                 */
1517                if (timeout < 0) {
1518                        printk(KERN_ERR "schedule_timeout: wrong timeout "
1519                                "value %lx\n", timeout);
1520                        dump_stack();
1521                        current->state = TASK_RUNNING;
1522                        goto out;
1523                }
1524        }
1525
1526        expire = timeout + jiffies;
1527
1528        setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
1529        __mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
1530        schedule();
1531        del_singleshot_timer_sync(&timer);
1532
1533        /* Remove the timer from the object tracker */
1534        destroy_timer_on_stack(&timer);
1535
1536        timeout = expire - jiffies;
1537
1538 out:
1539        return timeout < 0 ? 0 : timeout;
1540}
1541EXPORT_SYMBOL(schedule_timeout);
1542
1543/*
1544 * We can use __set_current_state() here because schedule_timeout() calls
1545 * schedule() unconditionally.
1546 */
1547signed long __sched schedule_timeout_interruptible(signed long timeout)
1548{
1549        __set_current_state(TASK_INTERRUPTIBLE);
1550        return schedule_timeout(timeout);
1551}
1552EXPORT_SYMBOL(schedule_timeout_interruptible);
1553
1554signed long __sched schedule_timeout_killable(signed long timeout)
1555{
1556        __set_current_state(TASK_KILLABLE);
1557        return schedule_timeout(timeout);
1558}
1559EXPORT_SYMBOL(schedule_timeout_killable);
1560
1561signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1562{
1563        __set_current_state(TASK_UNINTERRUPTIBLE);
1564        return schedule_timeout(timeout);
1565}
1566EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1567
1568/* Thread ID - the internal kernel "pid" */
1569SYSCALL_DEFINE0(gettid)
1570{
1571        return task_pid_vnr(current);
1572}
1573
1574/**
1575 * do_sysinfo - fill in sysinfo struct
1576 * @info: pointer to buffer to fill
1577 */
1578int do_sysinfo(struct sysinfo *info)
1579{
1580        unsigned long mem_total, sav_total;
1581        unsigned int mem_unit, bitcount;
1582        struct timespec tp;
1583
1584        memset(info, 0, sizeof(struct sysinfo));
1585
1586        ktime_get_ts(&tp);
1587        monotonic_to_bootbased(&tp);
1588        info->uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);
1589
1590        get_avenrun(info->loads, 0, SI_LOAD_SHIFT - FSHIFT);
1591
1592        info->procs = nr_threads;
1593
1594        si_meminfo(info);
1595        si_swapinfo(info);
1596
1597        /*
1598         * If the sum of all the available memory (i.e. ram + swap)
1599         * is less than can be stored in a 32 bit unsigned long then
1600         * we can be binary compatible with 2.2.x kernels.  If not,
1601         * well, in that case 2.2.x was broken anyways...
1602         *
1603         *  -Erik Andersen <andersee@debian.org>
1604         */
1605
1606        mem_total = info->totalram + info->totalswap;
1607        if (mem_total < info->totalram || mem_total < info->totalswap)
1608                goto out;
1609        bitcount = 0;
1610        mem_unit = info->mem_unit;
1611        while (mem_unit > 1) {
1612                bitcount++;
1613                mem_unit >>= 1;
1614                sav_total = mem_total;
1615                mem_total <<= 1;
1616                if (mem_total < sav_total)
1617                        goto out;
1618        }
1619
1620        /*
1621         * If mem_total did not overflow, multiply all memory values by
1622         * info->mem_unit and set it to 1.  This leaves things compatible
1623         * with 2.2.x, and also retains compatibility with earlier 2.4.x
1624         * kernels...
1625         */
1626
1627        info->mem_unit = 1;
1628        info->totalram <<= bitcount;
1629        info->freeram <<= bitcount;
1630        info->sharedram <<= bitcount;
1631        info->bufferram <<= bitcount;
1632        info->totalswap <<= bitcount;
1633        info->freeswap <<= bitcount;
1634        info->totalhigh <<= bitcount;
1635        info->freehigh <<= bitcount;
1636
1637out:
1638        return 0;
1639}
1640
1641SYSCALL_DEFINE1(sysinfo, struct sysinfo __user *, info)
1642{
1643        struct sysinfo val;
1644
1645        do_sysinfo(&val);
1646
1647        if (copy_to_user(info, &val, sizeof(struct sysinfo)))
1648                return -EFAULT;
1649
1650        return 0;
1651}
1652
1653static int __cpuinit init_timers_cpu(int cpu)
1654{
1655        int j;
1656        struct tvec_base *base;
1657        static char __cpuinitdata tvec_base_done[NR_CPUS];
1658
1659        if (!tvec_base_done[cpu]) {
1660                static char boot_done;
1661
1662                if (boot_done) {
1663                        /*
1664                         * The APs use this path later in boot
1665                         */
1666                        base = kmalloc_node(sizeof(*base),
1667                                                GFP_KERNEL | __GFP_ZERO,
1668                                                cpu_to_node(cpu));
1669                        if (!base)
1670                                return -ENOMEM;
1671
1672                        /* Make sure that tvec_base is 2 byte aligned */
1673                        if (tbase_get_deferrable(base)) {
1674                                WARN_ON(1);
1675                                kfree(base);
1676                                return -ENOMEM;
1677                        }
1678                        per_cpu(tvec_bases, cpu) = base;
1679                } else {
1680                        /*
1681                         * This is for the boot CPU - we use compile-time
1682                         * static initialisation because per-cpu memory isn't
1683                         * ready yet and because the memory allocators are not
1684                         * initialised either.
1685                         */
1686                        boot_done = 1;
1687                        base = &boot_tvec_bases;
1688                }
1689                tvec_base_done[cpu] = 1;
1690        } else {
1691                base = per_cpu(tvec_bases, cpu);
1692        }
1693
1694        spin_lock_init(&base->lock);
1695
1696        for (j = 0; j < TVN_SIZE; j++) {
1697                INIT_LIST_HEAD(base->tv5.vec + j);
1698                INIT_LIST_HEAD(base->tv4.vec + j);
1699                INIT_LIST_HEAD(base->tv3.vec + j);
1700                INIT_LIST_HEAD(base->tv2.vec + j);
1701        }
1702        for (j = 0; j < TVR_SIZE; j++)
1703                INIT_LIST_HEAD(base->tv1.vec + j);
1704
1705        base->timer_jiffies = jiffies;
1706        base->next_timer = base->timer_jiffies;
1707        return 0;
1708}
1709
1710#ifdef CONFIG_HOTPLUG_CPU
1711static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)
1712{
1713        struct timer_list *timer;
1714
1715        while (!list_empty(head)) {
1716                timer = list_first_entry(head, struct timer_list, entry);
1717                detach_timer(timer, 0);
1718                timer_set_base(timer, new_base);
1719                if (time_before(timer->expires, new_base->next_timer) &&
1720                    !tbase_get_deferrable(timer->base))
1721                        new_base->next_timer = timer->expires;
1722                internal_add_timer(new_base, timer);
1723        }
1724}
1725
1726static void __cpuinit migrate_timers(int cpu)
1727{
1728        struct tvec_base *old_base;
1729        struct tvec_base *new_base;
1730        int i;
1731
1732        BUG_ON(cpu_online(cpu));
1733        old_base = per_cpu(tvec_bases, cpu);
1734        new_base = get_cpu_var(tvec_bases);
1735        /*
1736         * The caller is globally serialized and nobody else
1737         * takes two locks at once, deadlock is not possible.
1738         */
1739        spin_lock_irq(&new_base->lock);
1740        spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1741
1742        BUG_ON(old_base->running_timer);
1743
1744        for (i = 0; i < TVR_SIZE; i++)
1745                migrate_timer_list(new_base, old_base->tv1.vec + i);
1746        for (i = 0; i < TVN_SIZE; i++) {
1747                migrate_timer_list(new_base, old_base->tv2.vec + i);
1748                migrate_timer_list(new_base, old_base->tv3.vec + i);
1749                migrate_timer_list(new_base, old_base->tv4.vec + i);
1750                migrate_timer_list(new_base, old_base->tv5.vec + i);
1751        }
1752
1753        spin_unlock(&old_base->lock);
1754        spin_unlock_irq(&new_base->lock);
1755        put_cpu_var(tvec_bases);
1756}
1757#endif /* CONFIG_HOTPLUG_CPU */
1758
1759static int __cpuinit timer_cpu_notify(struct notifier_block *self,
1760                                unsigned long action, void *hcpu)
1761{
1762        long cpu = (long)hcpu;
1763        int err;
1764
1765        switch(action) {
1766        case CPU_UP_PREPARE:
1767        case CPU_UP_PREPARE_FROZEN:
1768                err = init_timers_cpu(cpu);
1769                if (err < 0)
1770                        return notifier_from_errno(err);
1771                break;
1772#ifdef CONFIG_HOTPLUG_CPU
1773        case CPU_DEAD:
1774        case CPU_DEAD_FROZEN:
1775                migrate_timers(cpu);
1776                break;
1777#endif
1778        default:
1779                break;
1780        }
1781        return NOTIFY_OK;
1782}
1783
1784static struct notifier_block __cpuinitdata timers_nb = {
1785        .notifier_call  = timer_cpu_notify,
1786};
1787
1788
1789void __init init_timers(void)
1790{
1791        int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
1792                                (void *)(long)smp_processor_id());
1793
1794        init_timer_stats();
1795
1796        BUG_ON(err != NOTIFY_OK);
1797        register_cpu_notifier(&timers_nb);
1798        open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
1799}
1800
1801/**
1802 * msleep - sleep safely even with waitqueue interruptions
1803 * @msecs: Time in milliseconds to sleep for
1804 */
1805void msleep(unsigned int msecs)
1806{
1807        unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1808
1809        while (timeout)
1810                timeout = schedule_timeout_uninterruptible(timeout);
1811}
1812
1813EXPORT_SYMBOL(msleep);
1814
1815/**
1816 * msleep_interruptible - sleep waiting for signals
1817 * @msecs: Time in milliseconds to sleep for
1818 */
1819unsigned long msleep_interruptible(unsigned int msecs)
1820{
1821        unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1822
1823        while (timeout && !signal_pending(current))
1824                timeout = schedule_timeout_interruptible(timeout);
1825        return jiffies_to_msecs(timeout);
1826}
1827
1828EXPORT_SYMBOL(msleep_interruptible);
1829
1830static int __sched do_usleep_range(unsigned long min, unsigned long max)
1831{
1832        ktime_t kmin;
1833        unsigned long delta;
1834
1835        kmin = ktime_set(0, min * NSEC_PER_USEC);
1836        delta = (max - min) * NSEC_PER_USEC;
1837        return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
1838}
1839
1840/**
1841 * usleep_range - Drop in replacement for udelay where wakeup is flexible
1842 * @min: Minimum time in usecs to sleep
1843 * @max: Maximum time in usecs to sleep
1844 */
1845void usleep_range(unsigned long min, unsigned long max)
1846{
1847        __set_current_state(TASK_UNINTERRUPTIBLE);
1848        do_usleep_range(min, max);
1849}
1850EXPORT_SYMBOL(usleep_range);
1851
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