| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> |
| 4 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar |
| 5 | * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner |
| 6 | * |
| 7 | * No idle tick implementation for low and high resolution timers |
| 8 | * |
| 9 | * Started by: Thomas Gleixner and Ingo Molnar |
| 10 | */ |
| 11 | #include <linux/cpu.h> |
| 12 | #include <linux/err.h> |
| 13 | #include <linux/hrtimer.h> |
| 14 | #include <linux/interrupt.h> |
| 15 | #include <linux/kernel_stat.h> |
| 16 | #include <linux/percpu.h> |
| 17 | #include <linux/nmi.h> |
| 18 | #include <linux/profile.h> |
| 19 | #include <linux/sched/signal.h> |
| 20 | #include <linux/sched/clock.h> |
| 21 | #include <linux/sched/stat.h> |
| 22 | #include <linux/sched/nohz.h> |
| 23 | #include <linux/sched/loadavg.h> |
| 24 | #include <linux/module.h> |
| 25 | #include <linux/irq_work.h> |
| 26 | #include <linux/posix-timers.h> |
| 27 | #include <linux/context_tracking.h> |
| 28 | #include <linux/mm.h> |
| 29 | |
| 30 | #include <asm/irq_regs.h> |
| 31 | |
| 32 | #include "tick-internal.h" |
| 33 | |
| 34 | #include <trace/events/timer.h> |
| 35 | |
| 36 | /* |
| 37 | * Per-CPU nohz control structure |
| 38 | */ |
| 39 | static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); |
| 40 | |
| 41 | struct tick_sched *tick_get_tick_sched(int cpu) |
| 42 | { |
| 43 | return &per_cpu(tick_cpu_sched, cpu); |
| 44 | } |
| 45 | |
| 46 | #if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS) |
| 47 | /* |
| 48 | * The time, when the last jiffy update happened. Write access must hold |
| 49 | * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a |
| 50 | * consistent view of jiffies and last_jiffies_update. |
| 51 | */ |
| 52 | static ktime_t last_jiffies_update; |
| 53 | |
| 54 | /* |
| 55 | * Must be called with interrupts disabled ! |
| 56 | */ |
| 57 | static void tick_do_update_jiffies64(ktime_t now) |
| 58 | { |
| 59 | unsigned long ticks = 1; |
| 60 | ktime_t delta, nextp; |
| 61 | |
| 62 | /* |
| 63 | * 64bit can do a quick check without holding jiffies lock and |
| 64 | * without looking at the sequence count. The smp_load_acquire() |
| 65 | * pairs with the update done later in this function. |
| 66 | * |
| 67 | * 32bit cannot do that because the store of tick_next_period |
| 68 | * consists of two 32bit stores and the first store could move it |
| 69 | * to a random point in the future. |
| 70 | */ |
| 71 | if (IS_ENABLED(CONFIG_64BIT)) { |
| 72 | if (ktime_before(now, smp_load_acquire(&tick_next_period))) |
| 73 | return; |
| 74 | } else { |
| 75 | unsigned int seq; |
| 76 | |
| 77 | /* |
| 78 | * Avoid contention on jiffies_lock and protect the quick |
| 79 | * check with the sequence count. |
| 80 | */ |
| 81 | do { |
| 82 | seq = read_seqcount_begin(&jiffies_seq); |
| 83 | nextp = tick_next_period; |
| 84 | } while (read_seqcount_retry(&jiffies_seq, seq)); |
| 85 | |
| 86 | if (ktime_before(now, nextp)) |
| 87 | return; |
| 88 | } |
| 89 | |
| 90 | /* Quick check failed, i.e. update is required. */ |
| 91 | raw_spin_lock(&jiffies_lock); |
| 92 | /* |
| 93 | * Reevaluate with the lock held. Another CPU might have done the |
| 94 | * update already. |
| 95 | */ |
| 96 | if (ktime_before(now, tick_next_period)) { |
| 97 | raw_spin_unlock(&jiffies_lock); |
| 98 | return; |
| 99 | } |
| 100 | |
| 101 | write_seqcount_begin(&jiffies_seq); |
| 102 | |
| 103 | delta = ktime_sub(now, tick_next_period); |
| 104 | if (unlikely(delta >= TICK_NSEC)) { |
| 105 | /* Slow path for long idle sleep times */ |
| 106 | s64 incr = TICK_NSEC; |
| 107 | |
| 108 | ticks += ktime_divns(delta, incr); |
| 109 | |
| 110 | last_jiffies_update = ktime_add_ns(last_jiffies_update, |
| 111 | incr * ticks); |
| 112 | } else { |
| 113 | last_jiffies_update = ktime_add_ns(last_jiffies_update, |
| 114 | TICK_NSEC); |
| 115 | } |
| 116 | |
| 117 | /* Advance jiffies to complete the jiffies_seq protected job */ |
| 118 | jiffies_64 += ticks; |
| 119 | |
| 120 | /* |
| 121 | * Keep the tick_next_period variable up to date. |
| 122 | */ |
| 123 | nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC); |
| 124 | |
| 125 | if (IS_ENABLED(CONFIG_64BIT)) { |
| 126 | /* |
| 127 | * Pairs with smp_load_acquire() in the lockless quick |
| 128 | * check above and ensures that the update to jiffies_64 is |
| 129 | * not reordered vs. the store to tick_next_period, neither |
| 130 | * by the compiler nor by the CPU. |
| 131 | */ |
| 132 | smp_store_release(&tick_next_period, nextp); |
| 133 | } else { |
| 134 | /* |
| 135 | * A plain store is good enough on 32bit as the quick check |
| 136 | * above is protected by the sequence count. |
| 137 | */ |
| 138 | tick_next_period = nextp; |
| 139 | } |
| 140 | |
| 141 | /* |
| 142 | * Release the sequence count. calc_global_load() below is not |
| 143 | * protected by it, but jiffies_lock needs to be held to prevent |
| 144 | * concurrent invocations. |
| 145 | */ |
| 146 | write_seqcount_end(&jiffies_seq); |
| 147 | |
| 148 | calc_global_load(); |
| 149 | |
| 150 | raw_spin_unlock(&jiffies_lock); |
| 151 | update_wall_time(); |
| 152 | } |
| 153 | |
| 154 | /* |
| 155 | * Initialize and return retrieve the jiffies update. |
| 156 | */ |
| 157 | static ktime_t tick_init_jiffy_update(void) |
| 158 | { |
| 159 | ktime_t period; |
| 160 | |
| 161 | raw_spin_lock(&jiffies_lock); |
| 162 | write_seqcount_begin(&jiffies_seq); |
| 163 | /* Did we start the jiffies update yet ? */ |
| 164 | if (last_jiffies_update == 0) { |
| 165 | u32 rem; |
| 166 | |
| 167 | /* |
| 168 | * Ensure that the tick is aligned to a multiple of |
| 169 | * TICK_NSEC. |
| 170 | */ |
| 171 | div_u64_rem(tick_next_period, TICK_NSEC, &rem); |
| 172 | if (rem) |
| 173 | tick_next_period += TICK_NSEC - rem; |
| 174 | |
| 175 | last_jiffies_update = tick_next_period; |
| 176 | } |
| 177 | period = last_jiffies_update; |
| 178 | write_seqcount_end(&jiffies_seq); |
| 179 | raw_spin_unlock(&jiffies_lock); |
| 180 | return period; |
| 181 | } |
| 182 | |
| 183 | #define MAX_STALLED_JIFFIES 5 |
| 184 | |
| 185 | static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now) |
| 186 | { |
| 187 | int cpu = smp_processor_id(); |
| 188 | |
| 189 | #ifdef CONFIG_NO_HZ_COMMON |
| 190 | /* |
| 191 | * Check if the do_timer duty was dropped. We don't care about |
| 192 | * concurrency: This happens only when the CPU in charge went |
| 193 | * into a long sleep. If two CPUs happen to assign themselves to |
| 194 | * this duty, then the jiffies update is still serialized by |
| 195 | * jiffies_lock. |
| 196 | * |
| 197 | * If nohz_full is enabled, this should not happen because the |
| 198 | * tick_do_timer_cpu never relinquishes. |
| 199 | */ |
| 200 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) { |
| 201 | #ifdef CONFIG_NO_HZ_FULL |
| 202 | WARN_ON_ONCE(tick_nohz_full_running); |
| 203 | #endif |
| 204 | tick_do_timer_cpu = cpu; |
| 205 | } |
| 206 | #endif |
| 207 | |
| 208 | /* Check, if the jiffies need an update */ |
| 209 | if (tick_do_timer_cpu == cpu) |
| 210 | tick_do_update_jiffies64(now); |
| 211 | |
| 212 | /* |
| 213 | * If jiffies update stalled for too long (timekeeper in stop_machine() |
| 214 | * or VMEXIT'ed for several msecs), force an update. |
| 215 | */ |
| 216 | if (ts->last_tick_jiffies != jiffies) { |
| 217 | ts->stalled_jiffies = 0; |
| 218 | ts->last_tick_jiffies = READ_ONCE(jiffies); |
| 219 | } else { |
| 220 | if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) { |
| 221 | tick_do_update_jiffies64(now); |
| 222 | ts->stalled_jiffies = 0; |
| 223 | ts->last_tick_jiffies = READ_ONCE(jiffies); |
| 224 | } |
| 225 | } |
| 226 | |
| 227 | if (ts->inidle) |
| 228 | ts->got_idle_tick = 1; |
| 229 | } |
| 230 | |
| 231 | static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) |
| 232 | { |
| 233 | #ifdef CONFIG_NO_HZ_COMMON |
| 234 | /* |
| 235 | * When we are idle and the tick is stopped, we have to touch |
| 236 | * the watchdog as we might not schedule for a really long |
| 237 | * time. This happens on complete idle SMP systems while |
| 238 | * waiting on the login prompt. We also increment the "start of |
| 239 | * idle" jiffy stamp so the idle accounting adjustment we do |
| 240 | * when we go busy again does not account too much ticks. |
| 241 | */ |
| 242 | if (ts->tick_stopped) { |
| 243 | touch_softlockup_watchdog_sched(); |
| 244 | if (is_idle_task(current)) |
| 245 | ts->idle_jiffies++; |
| 246 | /* |
| 247 | * In case the current tick fired too early past its expected |
| 248 | * expiration, make sure we don't bypass the next clock reprogramming |
| 249 | * to the same deadline. |
| 250 | */ |
| 251 | ts->next_tick = 0; |
| 252 | } |
| 253 | #endif |
| 254 | update_process_times(user_mode(regs)); |
| 255 | profile_tick(CPU_PROFILING); |
| 256 | } |
| 257 | #endif |
| 258 | |
| 259 | #ifdef CONFIG_NO_HZ_FULL |
| 260 | cpumask_var_t tick_nohz_full_mask; |
| 261 | EXPORT_SYMBOL_GPL(tick_nohz_full_mask); |
| 262 | bool tick_nohz_full_running; |
| 263 | EXPORT_SYMBOL_GPL(tick_nohz_full_running); |
| 264 | static atomic_t tick_dep_mask; |
| 265 | |
| 266 | static bool check_tick_dependency(atomic_t *dep) |
| 267 | { |
| 268 | int val = atomic_read(dep); |
| 269 | |
| 270 | if (val & TICK_DEP_MASK_POSIX_TIMER) { |
| 271 | trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER); |
| 272 | return true; |
| 273 | } |
| 274 | |
| 275 | if (val & TICK_DEP_MASK_PERF_EVENTS) { |
| 276 | trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS); |
| 277 | return true; |
| 278 | } |
| 279 | |
| 280 | if (val & TICK_DEP_MASK_SCHED) { |
| 281 | trace_tick_stop(0, TICK_DEP_MASK_SCHED); |
| 282 | return true; |
| 283 | } |
| 284 | |
| 285 | if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) { |
| 286 | trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE); |
| 287 | return true; |
| 288 | } |
| 289 | |
| 290 | if (val & TICK_DEP_MASK_RCU) { |
| 291 | trace_tick_stop(0, TICK_DEP_MASK_RCU); |
| 292 | return true; |
| 293 | } |
| 294 | |
| 295 | if (val & TICK_DEP_MASK_RCU_EXP) { |
| 296 | trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP); |
| 297 | return true; |
| 298 | } |
| 299 | |
| 300 | return false; |
| 301 | } |
| 302 | |
| 303 | static bool can_stop_full_tick(int cpu, struct tick_sched *ts) |
| 304 | { |
| 305 | lockdep_assert_irqs_disabled(); |
| 306 | |
| 307 | if (unlikely(!cpu_online(cpu))) |
| 308 | return false; |
| 309 | |
| 310 | if (check_tick_dependency(&tick_dep_mask)) |
| 311 | return false; |
| 312 | |
| 313 | if (check_tick_dependency(&ts->tick_dep_mask)) |
| 314 | return false; |
| 315 | |
| 316 | if (check_tick_dependency(¤t->tick_dep_mask)) |
| 317 | return false; |
| 318 | |
| 319 | if (check_tick_dependency(¤t->signal->tick_dep_mask)) |
| 320 | return false; |
| 321 | |
| 322 | return true; |
| 323 | } |
| 324 | |
| 325 | static void nohz_full_kick_func(struct irq_work *work) |
| 326 | { |
| 327 | /* Empty, the tick restart happens on tick_nohz_irq_exit() */ |
| 328 | } |
| 329 | |
| 330 | static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = |
| 331 | IRQ_WORK_INIT_HARD(nohz_full_kick_func); |
| 332 | |
| 333 | /* |
| 334 | * Kick this CPU if it's full dynticks in order to force it to |
| 335 | * re-evaluate its dependency on the tick and restart it if necessary. |
| 336 | * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(), |
| 337 | * is NMI safe. |
| 338 | */ |
| 339 | static void tick_nohz_full_kick(void) |
| 340 | { |
| 341 | if (!tick_nohz_full_cpu(smp_processor_id())) |
| 342 | return; |
| 343 | |
| 344 | irq_work_queue(this_cpu_ptr(&nohz_full_kick_work)); |
| 345 | } |
| 346 | |
| 347 | /* |
| 348 | * Kick the CPU if it's full dynticks in order to force it to |
| 349 | * re-evaluate its dependency on the tick and restart it if necessary. |
| 350 | */ |
| 351 | void tick_nohz_full_kick_cpu(int cpu) |
| 352 | { |
| 353 | if (!tick_nohz_full_cpu(cpu)) |
| 354 | return; |
| 355 | |
| 356 | irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); |
| 357 | } |
| 358 | |
| 359 | static void tick_nohz_kick_task(struct task_struct *tsk) |
| 360 | { |
| 361 | int cpu; |
| 362 | |
| 363 | /* |
| 364 | * If the task is not running, run_posix_cpu_timers() |
| 365 | * has nothing to elapse, IPI can then be spared. |
| 366 | * |
| 367 | * activate_task() STORE p->tick_dep_mask |
| 368 | * STORE p->on_rq |
| 369 | * __schedule() (switch to task 'p') smp_mb() (atomic_fetch_or()) |
| 370 | * LOCK rq->lock LOAD p->on_rq |
| 371 | * smp_mb__after_spin_lock() |
| 372 | * tick_nohz_task_switch() |
| 373 | * LOAD p->tick_dep_mask |
| 374 | */ |
| 375 | if (!sched_task_on_rq(tsk)) |
| 376 | return; |
| 377 | |
| 378 | /* |
| 379 | * If the task concurrently migrates to another CPU, |
| 380 | * we guarantee it sees the new tick dependency upon |
| 381 | * schedule. |
| 382 | * |
| 383 | * set_task_cpu(p, cpu); |
| 384 | * STORE p->cpu = @cpu |
| 385 | * __schedule() (switch to task 'p') |
| 386 | * LOCK rq->lock |
| 387 | * smp_mb__after_spin_lock() STORE p->tick_dep_mask |
| 388 | * tick_nohz_task_switch() smp_mb() (atomic_fetch_or()) |
| 389 | * LOAD p->tick_dep_mask LOAD p->cpu |
| 390 | */ |
| 391 | cpu = task_cpu(tsk); |
| 392 | |
| 393 | preempt_disable(); |
| 394 | if (cpu_online(cpu)) |
| 395 | tick_nohz_full_kick_cpu(cpu); |
| 396 | preempt_enable(); |
| 397 | } |
| 398 | |
| 399 | /* |
| 400 | * Kick all full dynticks CPUs in order to force these to re-evaluate |
| 401 | * their dependency on the tick and restart it if necessary. |
| 402 | */ |
| 403 | static void tick_nohz_full_kick_all(void) |
| 404 | { |
| 405 | int cpu; |
| 406 | |
| 407 | if (!tick_nohz_full_running) |
| 408 | return; |
| 409 | |
| 410 | preempt_disable(); |
| 411 | for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask) |
| 412 | tick_nohz_full_kick_cpu(cpu); |
| 413 | preempt_enable(); |
| 414 | } |
| 415 | |
| 416 | static void tick_nohz_dep_set_all(atomic_t *dep, |
| 417 | enum tick_dep_bits bit) |
| 418 | { |
| 419 | int prev; |
| 420 | |
| 421 | prev = atomic_fetch_or(BIT(bit), dep); |
| 422 | if (!prev) |
| 423 | tick_nohz_full_kick_all(); |
| 424 | } |
| 425 | |
| 426 | /* |
| 427 | * Set a global tick dependency. Used by perf events that rely on freq and |
| 428 | * by unstable clock. |
| 429 | */ |
| 430 | void tick_nohz_dep_set(enum tick_dep_bits bit) |
| 431 | { |
| 432 | tick_nohz_dep_set_all(&tick_dep_mask, bit); |
| 433 | } |
| 434 | |
| 435 | void tick_nohz_dep_clear(enum tick_dep_bits bit) |
| 436 | { |
| 437 | atomic_andnot(BIT(bit), &tick_dep_mask); |
| 438 | } |
| 439 | |
| 440 | /* |
| 441 | * Set per-CPU tick dependency. Used by scheduler and perf events in order to |
| 442 | * manage events throttling. |
| 443 | */ |
| 444 | void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) |
| 445 | { |
| 446 | int prev; |
| 447 | struct tick_sched *ts; |
| 448 | |
| 449 | ts = per_cpu_ptr(&tick_cpu_sched, cpu); |
| 450 | |
| 451 | prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask); |
| 452 | if (!prev) { |
| 453 | preempt_disable(); |
| 454 | /* Perf needs local kick that is NMI safe */ |
| 455 | if (cpu == smp_processor_id()) { |
| 456 | tick_nohz_full_kick(); |
| 457 | } else { |
| 458 | /* Remote irq work not NMI-safe */ |
| 459 | if (!WARN_ON_ONCE(in_nmi())) |
| 460 | tick_nohz_full_kick_cpu(cpu); |
| 461 | } |
| 462 | preempt_enable(); |
| 463 | } |
| 464 | } |
| 465 | EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu); |
| 466 | |
| 467 | void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) |
| 468 | { |
| 469 | struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); |
| 470 | |
| 471 | atomic_andnot(BIT(bit), &ts->tick_dep_mask); |
| 472 | } |
| 473 | EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu); |
| 474 | |
| 475 | /* |
| 476 | * Set a per-task tick dependency. RCU need this. Also posix CPU timers |
| 477 | * in order to elapse per task timers. |
| 478 | */ |
| 479 | void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) |
| 480 | { |
| 481 | if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask)) |
| 482 | tick_nohz_kick_task(tsk); |
| 483 | } |
| 484 | EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task); |
| 485 | |
| 486 | void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit) |
| 487 | { |
| 488 | atomic_andnot(BIT(bit), &tsk->tick_dep_mask); |
| 489 | } |
| 490 | EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task); |
| 491 | |
| 492 | /* |
| 493 | * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse |
| 494 | * per process timers. |
| 495 | */ |
| 496 | void tick_nohz_dep_set_signal(struct task_struct *tsk, |
| 497 | enum tick_dep_bits bit) |
| 498 | { |
| 499 | int prev; |
| 500 | struct signal_struct *sig = tsk->signal; |
| 501 | |
| 502 | prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask); |
| 503 | if (!prev) { |
| 504 | struct task_struct *t; |
| 505 | |
| 506 | lockdep_assert_held(&tsk->sighand->siglock); |
| 507 | __for_each_thread(sig, t) |
| 508 | tick_nohz_kick_task(t); |
| 509 | } |
| 510 | } |
| 511 | |
| 512 | void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit) |
| 513 | { |
| 514 | atomic_andnot(BIT(bit), &sig->tick_dep_mask); |
| 515 | } |
| 516 | |
| 517 | /* |
| 518 | * Re-evaluate the need for the tick as we switch the current task. |
| 519 | * It might need the tick due to per task/process properties: |
| 520 | * perf events, posix CPU timers, ... |
| 521 | */ |
| 522 | void __tick_nohz_task_switch(void) |
| 523 | { |
| 524 | struct tick_sched *ts; |
| 525 | |
| 526 | if (!tick_nohz_full_cpu(smp_processor_id())) |
| 527 | return; |
| 528 | |
| 529 | ts = this_cpu_ptr(&tick_cpu_sched); |
| 530 | |
| 531 | if (ts->tick_stopped) { |
| 532 | if (atomic_read(¤t->tick_dep_mask) || |
| 533 | atomic_read(¤t->signal->tick_dep_mask)) |
| 534 | tick_nohz_full_kick(); |
| 535 | } |
| 536 | } |
| 537 | |
| 538 | /* Get the boot-time nohz CPU list from the kernel parameters. */ |
| 539 | void __init tick_nohz_full_setup(cpumask_var_t cpumask) |
| 540 | { |
| 541 | alloc_bootmem_cpumask_var(&tick_nohz_full_mask); |
| 542 | cpumask_copy(tick_nohz_full_mask, cpumask); |
| 543 | tick_nohz_full_running = true; |
| 544 | } |
| 545 | |
| 546 | bool tick_nohz_cpu_hotpluggable(unsigned int cpu) |
| 547 | { |
| 548 | /* |
| 549 | * The tick_do_timer_cpu CPU handles housekeeping duty (unbound |
| 550 | * timers, workqueues, timekeeping, ...) on behalf of full dynticks |
| 551 | * CPUs. It must remain online when nohz full is enabled. |
| 552 | */ |
| 553 | if (tick_nohz_full_running && tick_do_timer_cpu == cpu) |
| 554 | return false; |
| 555 | return true; |
| 556 | } |
| 557 | |
| 558 | static int tick_nohz_cpu_down(unsigned int cpu) |
| 559 | { |
| 560 | return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY; |
| 561 | } |
| 562 | |
| 563 | void __init tick_nohz_init(void) |
| 564 | { |
| 565 | int cpu, ret; |
| 566 | |
| 567 | if (!tick_nohz_full_running) |
| 568 | return; |
| 569 | |
| 570 | /* |
| 571 | * Full dynticks uses irq work to drive the tick rescheduling on safe |
| 572 | * locking contexts. But then we need irq work to raise its own |
| 573 | * interrupts to avoid circular dependency on the tick |
| 574 | */ |
| 575 | if (!arch_irq_work_has_interrupt()) { |
| 576 | pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n"); |
| 577 | cpumask_clear(tick_nohz_full_mask); |
| 578 | tick_nohz_full_running = false; |
| 579 | return; |
| 580 | } |
| 581 | |
| 582 | if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) && |
| 583 | !IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) { |
| 584 | cpu = smp_processor_id(); |
| 585 | |
| 586 | if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { |
| 587 | pr_warn("NO_HZ: Clearing %d from nohz_full range " |
| 588 | "for timekeeping\n", cpu); |
| 589 | cpumask_clear_cpu(cpu, tick_nohz_full_mask); |
| 590 | } |
| 591 | } |
| 592 | |
| 593 | for_each_cpu(cpu, tick_nohz_full_mask) |
| 594 | ct_cpu_track_user(cpu); |
| 595 | |
| 596 | ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, |
| 597 | "kernel/nohz:predown", NULL, |
| 598 | tick_nohz_cpu_down); |
| 599 | WARN_ON(ret < 0); |
| 600 | pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n", |
| 601 | cpumask_pr_args(tick_nohz_full_mask)); |
| 602 | } |
| 603 | #endif |
| 604 | |
| 605 | /* |
| 606 | * NOHZ - aka dynamic tick functionality |
| 607 | */ |
| 608 | #ifdef CONFIG_NO_HZ_COMMON |
| 609 | /* |
| 610 | * NO HZ enabled ? |
| 611 | */ |
| 612 | bool tick_nohz_enabled __read_mostly = true; |
| 613 | unsigned long tick_nohz_active __read_mostly; |
| 614 | /* |
| 615 | * Enable / Disable tickless mode |
| 616 | */ |
| 617 | static int __init setup_tick_nohz(char *str) |
| 618 | { |
| 619 | return (kstrtobool(str, &tick_nohz_enabled) == 0); |
| 620 | } |
| 621 | |
| 622 | __setup("nohz=", setup_tick_nohz); |
| 623 | |
| 624 | bool tick_nohz_tick_stopped(void) |
| 625 | { |
| 626 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 627 | |
| 628 | return ts->tick_stopped; |
| 629 | } |
| 630 | |
| 631 | bool tick_nohz_tick_stopped_cpu(int cpu) |
| 632 | { |
| 633 | struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); |
| 634 | |
| 635 | return ts->tick_stopped; |
| 636 | } |
| 637 | |
| 638 | /** |
| 639 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted |
| 640 | * |
| 641 | * Called from interrupt entry when the CPU was idle |
| 642 | * |
| 643 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies |
| 644 | * must be updated. Otherwise an interrupt handler could use a stale jiffy |
| 645 | * value. We do this unconditionally on any CPU, as we don't know whether the |
| 646 | * CPU, which has the update task assigned is in a long sleep. |
| 647 | */ |
| 648 | static void tick_nohz_update_jiffies(ktime_t now) |
| 649 | { |
| 650 | unsigned long flags; |
| 651 | |
| 652 | __this_cpu_write(tick_cpu_sched.idle_waketime, now); |
| 653 | |
| 654 | local_irq_save(flags); |
| 655 | tick_do_update_jiffies64(now); |
| 656 | local_irq_restore(flags); |
| 657 | |
| 658 | touch_softlockup_watchdog_sched(); |
| 659 | } |
| 660 | |
| 661 | static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now) |
| 662 | { |
| 663 | ktime_t delta; |
| 664 | |
| 665 | if (WARN_ON_ONCE(!ts->idle_active)) |
| 666 | return; |
| 667 | |
| 668 | delta = ktime_sub(now, ts->idle_entrytime); |
| 669 | |
| 670 | write_seqcount_begin(&ts->idle_sleeptime_seq); |
| 671 | if (nr_iowait_cpu(smp_processor_id()) > 0) |
| 672 | ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
| 673 | else |
| 674 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); |
| 675 | |
| 676 | ts->idle_entrytime = now; |
| 677 | ts->idle_active = 0; |
| 678 | write_seqcount_end(&ts->idle_sleeptime_seq); |
| 679 | |
| 680 | sched_clock_idle_wakeup_event(); |
| 681 | } |
| 682 | |
| 683 | static void tick_nohz_start_idle(struct tick_sched *ts) |
| 684 | { |
| 685 | write_seqcount_begin(&ts->idle_sleeptime_seq); |
| 686 | ts->idle_entrytime = ktime_get(); |
| 687 | ts->idle_active = 1; |
| 688 | write_seqcount_end(&ts->idle_sleeptime_seq); |
| 689 | |
| 690 | sched_clock_idle_sleep_event(); |
| 691 | } |
| 692 | |
| 693 | static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime, |
| 694 | bool compute_delta, u64 *last_update_time) |
| 695 | { |
| 696 | ktime_t now, idle; |
| 697 | unsigned int seq; |
| 698 | |
| 699 | if (!tick_nohz_active) |
| 700 | return -1; |
| 701 | |
| 702 | now = ktime_get(); |
| 703 | if (last_update_time) |
| 704 | *last_update_time = ktime_to_us(now); |
| 705 | |
| 706 | do { |
| 707 | seq = read_seqcount_begin(&ts->idle_sleeptime_seq); |
| 708 | |
| 709 | if (ts->idle_active && compute_delta) { |
| 710 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); |
| 711 | |
| 712 | idle = ktime_add(*sleeptime, delta); |
| 713 | } else { |
| 714 | idle = *sleeptime; |
| 715 | } |
| 716 | } while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq)); |
| 717 | |
| 718 | return ktime_to_us(idle); |
| 719 | |
| 720 | } |
| 721 | |
| 722 | /** |
| 723 | * get_cpu_idle_time_us - get the total idle time of a CPU |
| 724 | * @cpu: CPU number to query |
| 725 | * @last_update_time: variable to store update time in. Do not update |
| 726 | * counters if NULL. |
| 727 | * |
| 728 | * Return the cumulative idle time (since boot) for a given |
| 729 | * CPU, in microseconds. Note this is partially broken due to |
| 730 | * the counter of iowait tasks that can be remotely updated without |
| 731 | * any synchronization. Therefore it is possible to observe backward |
| 732 | * values within two consecutive reads. |
| 733 | * |
| 734 | * This time is measured via accounting rather than sampling, |
| 735 | * and is as accurate as ktime_get() is. |
| 736 | * |
| 737 | * This function returns -1 if NOHZ is not enabled. |
| 738 | */ |
| 739 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) |
| 740 | { |
| 741 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 742 | |
| 743 | return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime, |
| 744 | !nr_iowait_cpu(cpu), last_update_time); |
| 745 | } |
| 746 | EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
| 747 | |
| 748 | /** |
| 749 | * get_cpu_iowait_time_us - get the total iowait time of a CPU |
| 750 | * @cpu: CPU number to query |
| 751 | * @last_update_time: variable to store update time in. Do not update |
| 752 | * counters if NULL. |
| 753 | * |
| 754 | * Return the cumulative iowait time (since boot) for a given |
| 755 | * CPU, in microseconds. Note this is partially broken due to |
| 756 | * the counter of iowait tasks that can be remotely updated without |
| 757 | * any synchronization. Therefore it is possible to observe backward |
| 758 | * values within two consecutive reads. |
| 759 | * |
| 760 | * This time is measured via accounting rather than sampling, |
| 761 | * and is as accurate as ktime_get() is. |
| 762 | * |
| 763 | * This function returns -1 if NOHZ is not enabled. |
| 764 | */ |
| 765 | u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) |
| 766 | { |
| 767 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 768 | |
| 769 | return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime, |
| 770 | nr_iowait_cpu(cpu), last_update_time); |
| 771 | } |
| 772 | EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); |
| 773 | |
| 774 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
| 775 | { |
| 776 | hrtimer_cancel(&ts->sched_timer); |
| 777 | hrtimer_set_expires(&ts->sched_timer, ts->last_tick); |
| 778 | |
| 779 | /* Forward the time to expire in the future */ |
| 780 | hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); |
| 781 | |
| 782 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
| 783 | hrtimer_start_expires(&ts->sched_timer, |
| 784 | HRTIMER_MODE_ABS_PINNED_HARD); |
| 785 | } else { |
| 786 | tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); |
| 787 | } |
| 788 | |
| 789 | /* |
| 790 | * Reset to make sure next tick stop doesn't get fooled by past |
| 791 | * cached clock deadline. |
| 792 | */ |
| 793 | ts->next_tick = 0; |
| 794 | } |
| 795 | |
| 796 | static inline bool local_timer_softirq_pending(void) |
| 797 | { |
| 798 | return local_softirq_pending() & BIT(TIMER_SOFTIRQ); |
| 799 | } |
| 800 | |
| 801 | static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu) |
| 802 | { |
| 803 | u64 basemono, next_tick, delta, expires; |
| 804 | unsigned long basejiff; |
| 805 | unsigned int seq; |
| 806 | |
| 807 | /* Read jiffies and the time when jiffies were updated last */ |
| 808 | do { |
| 809 | seq = read_seqcount_begin(&jiffies_seq); |
| 810 | basemono = last_jiffies_update; |
| 811 | basejiff = jiffies; |
| 812 | } while (read_seqcount_retry(&jiffies_seq, seq)); |
| 813 | ts->last_jiffies = basejiff; |
| 814 | ts->timer_expires_base = basemono; |
| 815 | |
| 816 | /* |
| 817 | * Keep the periodic tick, when RCU, architecture or irq_work |
| 818 | * requests it. |
| 819 | * Aside of that check whether the local timer softirq is |
| 820 | * pending. If so its a bad idea to call get_next_timer_interrupt() |
| 821 | * because there is an already expired timer, so it will request |
| 822 | * immediate expiry, which rearms the hardware timer with a |
| 823 | * minimal delta which brings us back to this place |
| 824 | * immediately. Lather, rinse and repeat... |
| 825 | */ |
| 826 | if (rcu_needs_cpu() || arch_needs_cpu() || |
| 827 | irq_work_needs_cpu() || local_timer_softirq_pending()) { |
| 828 | next_tick = basemono + TICK_NSEC; |
| 829 | } else { |
| 830 | /* |
| 831 | * Get the next pending timer. If high resolution |
| 832 | * timers are enabled this only takes the timer wheel |
| 833 | * timers into account. If high resolution timers are |
| 834 | * disabled this also looks at the next expiring |
| 835 | * hrtimer. |
| 836 | */ |
| 837 | next_tick = get_next_timer_interrupt(basejiff, basemono); |
| 838 | ts->next_timer = next_tick; |
| 839 | } |
| 840 | |
| 841 | /* |
| 842 | * If the tick is due in the next period, keep it ticking or |
| 843 | * force prod the timer. |
| 844 | */ |
| 845 | delta = next_tick - basemono; |
| 846 | if (delta <= (u64)TICK_NSEC) { |
| 847 | /* |
| 848 | * Tell the timer code that the base is not idle, i.e. undo |
| 849 | * the effect of get_next_timer_interrupt(): |
| 850 | */ |
| 851 | timer_clear_idle(); |
| 852 | /* |
| 853 | * We've not stopped the tick yet, and there's a timer in the |
| 854 | * next period, so no point in stopping it either, bail. |
| 855 | */ |
| 856 | if (!ts->tick_stopped) { |
| 857 | ts->timer_expires = 0; |
| 858 | goto out; |
| 859 | } |
| 860 | } |
| 861 | |
| 862 | /* |
| 863 | * If this CPU is the one which had the do_timer() duty last, we limit |
| 864 | * the sleep time to the timekeeping max_deferment value. |
| 865 | * Otherwise we can sleep as long as we want. |
| 866 | */ |
| 867 | delta = timekeeping_max_deferment(); |
| 868 | if (cpu != tick_do_timer_cpu && |
| 869 | (tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last)) |
| 870 | delta = KTIME_MAX; |
| 871 | |
| 872 | /* Calculate the next expiry time */ |
| 873 | if (delta < (KTIME_MAX - basemono)) |
| 874 | expires = basemono + delta; |
| 875 | else |
| 876 | expires = KTIME_MAX; |
| 877 | |
| 878 | ts->timer_expires = min_t(u64, expires, next_tick); |
| 879 | |
| 880 | out: |
| 881 | return ts->timer_expires; |
| 882 | } |
| 883 | |
| 884 | static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu) |
| 885 | { |
| 886 | struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
| 887 | u64 basemono = ts->timer_expires_base; |
| 888 | u64 expires = ts->timer_expires; |
| 889 | ktime_t tick = expires; |
| 890 | |
| 891 | /* Make sure we won't be trying to stop it twice in a row. */ |
| 892 | ts->timer_expires_base = 0; |
| 893 | |
| 894 | /* |
| 895 | * If this CPU is the one which updates jiffies, then give up |
| 896 | * the assignment and let it be taken by the CPU which runs |
| 897 | * the tick timer next, which might be this CPU as well. If we |
| 898 | * don't drop this here the jiffies might be stale and |
| 899 | * do_timer() never invoked. Keep track of the fact that it |
| 900 | * was the one which had the do_timer() duty last. |
| 901 | */ |
| 902 | if (cpu == tick_do_timer_cpu) { |
| 903 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
| 904 | ts->do_timer_last = 1; |
| 905 | } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { |
| 906 | ts->do_timer_last = 0; |
| 907 | } |
| 908 | |
| 909 | /* Skip reprogram of event if its not changed */ |
| 910 | if (ts->tick_stopped && (expires == ts->next_tick)) { |
| 911 | /* Sanity check: make sure clockevent is actually programmed */ |
| 912 | if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer)) |
| 913 | return; |
| 914 | |
| 915 | WARN_ON_ONCE(1); |
| 916 | printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n", |
| 917 | basemono, ts->next_tick, dev->next_event, |
| 918 | hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer)); |
| 919 | } |
| 920 | |
| 921 | /* |
| 922 | * nohz_stop_sched_tick can be called several times before |
| 923 | * the nohz_restart_sched_tick is called. This happens when |
| 924 | * interrupts arrive which do not cause a reschedule. In the |
| 925 | * first call we save the current tick time, so we can restart |
| 926 | * the scheduler tick in nohz_restart_sched_tick. |
| 927 | */ |
| 928 | if (!ts->tick_stopped) { |
| 929 | calc_load_nohz_start(); |
| 930 | quiet_vmstat(); |
| 931 | |
| 932 | ts->last_tick = hrtimer_get_expires(&ts->sched_timer); |
| 933 | ts->tick_stopped = 1; |
| 934 | trace_tick_stop(1, TICK_DEP_MASK_NONE); |
| 935 | } |
| 936 | |
| 937 | ts->next_tick = tick; |
| 938 | |
| 939 | /* |
| 940 | * If the expiration time == KTIME_MAX, then we simply stop |
| 941 | * the tick timer. |
| 942 | */ |
| 943 | if (unlikely(expires == KTIME_MAX)) { |
| 944 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
| 945 | hrtimer_cancel(&ts->sched_timer); |
| 946 | else |
| 947 | tick_program_event(KTIME_MAX, 1); |
| 948 | return; |
| 949 | } |
| 950 | |
| 951 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
| 952 | hrtimer_start(&ts->sched_timer, tick, |
| 953 | HRTIMER_MODE_ABS_PINNED_HARD); |
| 954 | } else { |
| 955 | hrtimer_set_expires(&ts->sched_timer, tick); |
| 956 | tick_program_event(tick, 1); |
| 957 | } |
| 958 | } |
| 959 | |
| 960 | static void tick_nohz_retain_tick(struct tick_sched *ts) |
| 961 | { |
| 962 | ts->timer_expires_base = 0; |
| 963 | } |
| 964 | |
| 965 | #ifdef CONFIG_NO_HZ_FULL |
| 966 | static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu) |
| 967 | { |
| 968 | if (tick_nohz_next_event(ts, cpu)) |
| 969 | tick_nohz_stop_tick(ts, cpu); |
| 970 | else |
| 971 | tick_nohz_retain_tick(ts); |
| 972 | } |
| 973 | #endif /* CONFIG_NO_HZ_FULL */ |
| 974 | |
| 975 | static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) |
| 976 | { |
| 977 | /* Update jiffies first */ |
| 978 | tick_do_update_jiffies64(now); |
| 979 | |
| 980 | /* |
| 981 | * Clear the timer idle flag, so we avoid IPIs on remote queueing and |
| 982 | * the clock forward checks in the enqueue path: |
| 983 | */ |
| 984 | timer_clear_idle(); |
| 985 | |
| 986 | calc_load_nohz_stop(); |
| 987 | touch_softlockup_watchdog_sched(); |
| 988 | /* |
| 989 | * Cancel the scheduled timer and restore the tick |
| 990 | */ |
| 991 | ts->tick_stopped = 0; |
| 992 | tick_nohz_restart(ts, now); |
| 993 | } |
| 994 | |
| 995 | static void __tick_nohz_full_update_tick(struct tick_sched *ts, |
| 996 | ktime_t now) |
| 997 | { |
| 998 | #ifdef CONFIG_NO_HZ_FULL |
| 999 | int cpu = smp_processor_id(); |
| 1000 | |
| 1001 | if (can_stop_full_tick(cpu, ts)) |
| 1002 | tick_nohz_stop_sched_tick(ts, cpu); |
| 1003 | else if (ts->tick_stopped) |
| 1004 | tick_nohz_restart_sched_tick(ts, now); |
| 1005 | #endif |
| 1006 | } |
| 1007 | |
| 1008 | static void tick_nohz_full_update_tick(struct tick_sched *ts) |
| 1009 | { |
| 1010 | if (!tick_nohz_full_cpu(smp_processor_id())) |
| 1011 | return; |
| 1012 | |
| 1013 | if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) |
| 1014 | return; |
| 1015 | |
| 1016 | __tick_nohz_full_update_tick(ts, ktime_get()); |
| 1017 | } |
| 1018 | |
| 1019 | /* |
| 1020 | * A pending softirq outside an IRQ (or softirq disabled section) context |
| 1021 | * should be waiting for ksoftirqd to handle it. Therefore we shouldn't |
| 1022 | * reach here due to the need_resched() early check in can_stop_idle_tick(). |
| 1023 | * |
| 1024 | * However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the |
| 1025 | * cpu_down() process, softirqs can still be raised while ksoftirqd is parked, |
| 1026 | * triggering the below since wakep_softirqd() is ignored. |
| 1027 | * |
| 1028 | */ |
| 1029 | static bool report_idle_softirq(void) |
| 1030 | { |
| 1031 | static int ratelimit; |
| 1032 | unsigned int pending = local_softirq_pending(); |
| 1033 | |
| 1034 | if (likely(!pending)) |
| 1035 | return false; |
| 1036 | |
| 1037 | /* Some softirqs claim to be safe against hotplug and ksoftirqd parking */ |
| 1038 | if (!cpu_active(smp_processor_id())) { |
| 1039 | pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK; |
| 1040 | if (!pending) |
| 1041 | return false; |
| 1042 | } |
| 1043 | |
| 1044 | if (ratelimit >= 10) |
| 1045 | return false; |
| 1046 | |
| 1047 | /* On RT, softirqs handling may be waiting on some lock */ |
| 1048 | if (local_bh_blocked()) |
| 1049 | return false; |
| 1050 | |
| 1051 | pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n", |
| 1052 | pending); |
| 1053 | ratelimit++; |
| 1054 | |
| 1055 | return true; |
| 1056 | } |
| 1057 | |
| 1058 | static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) |
| 1059 | { |
| 1060 | /* |
| 1061 | * If this CPU is offline and it is the one which updates |
| 1062 | * jiffies, then give up the assignment and let it be taken by |
| 1063 | * the CPU which runs the tick timer next. If we don't drop |
| 1064 | * this here the jiffies might be stale and do_timer() never |
| 1065 | * invoked. |
| 1066 | */ |
| 1067 | if (unlikely(!cpu_online(cpu))) { |
| 1068 | if (cpu == tick_do_timer_cpu) |
| 1069 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
| 1070 | /* |
| 1071 | * Make sure the CPU doesn't get fooled by obsolete tick |
| 1072 | * deadline if it comes back online later. |
| 1073 | */ |
| 1074 | ts->next_tick = 0; |
| 1075 | return false; |
| 1076 | } |
| 1077 | |
| 1078 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) |
| 1079 | return false; |
| 1080 | |
| 1081 | if (need_resched()) |
| 1082 | return false; |
| 1083 | |
| 1084 | if (unlikely(report_idle_softirq())) |
| 1085 | return false; |
| 1086 | |
| 1087 | if (tick_nohz_full_enabled()) { |
| 1088 | /* |
| 1089 | * Keep the tick alive to guarantee timekeeping progression |
| 1090 | * if there are full dynticks CPUs around |
| 1091 | */ |
| 1092 | if (tick_do_timer_cpu == cpu) |
| 1093 | return false; |
| 1094 | |
| 1095 | /* Should not happen for nohz-full */ |
| 1096 | if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) |
| 1097 | return false; |
| 1098 | } |
| 1099 | |
| 1100 | return true; |
| 1101 | } |
| 1102 | |
| 1103 | /** |
| 1104 | * tick_nohz_idle_stop_tick - stop the idle tick from the idle task |
| 1105 | * |
| 1106 | * When the next event is more than a tick into the future, stop the idle tick |
| 1107 | */ |
| 1108 | void tick_nohz_idle_stop_tick(void) |
| 1109 | { |
| 1110 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1111 | int cpu = smp_processor_id(); |
| 1112 | ktime_t expires; |
| 1113 | |
| 1114 | /* |
| 1115 | * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the |
| 1116 | * tick timer expiration time is known already. |
| 1117 | */ |
| 1118 | if (ts->timer_expires_base) |
| 1119 | expires = ts->timer_expires; |
| 1120 | else if (can_stop_idle_tick(cpu, ts)) |
| 1121 | expires = tick_nohz_next_event(ts, cpu); |
| 1122 | else |
| 1123 | return; |
| 1124 | |
| 1125 | ts->idle_calls++; |
| 1126 | |
| 1127 | if (expires > 0LL) { |
| 1128 | int was_stopped = ts->tick_stopped; |
| 1129 | |
| 1130 | tick_nohz_stop_tick(ts, cpu); |
| 1131 | |
| 1132 | ts->idle_sleeps++; |
| 1133 | ts->idle_expires = expires; |
| 1134 | |
| 1135 | if (!was_stopped && ts->tick_stopped) { |
| 1136 | ts->idle_jiffies = ts->last_jiffies; |
| 1137 | nohz_balance_enter_idle(cpu); |
| 1138 | } |
| 1139 | } else { |
| 1140 | tick_nohz_retain_tick(ts); |
| 1141 | } |
| 1142 | } |
| 1143 | |
| 1144 | void tick_nohz_idle_retain_tick(void) |
| 1145 | { |
| 1146 | tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched)); |
| 1147 | /* |
| 1148 | * Undo the effect of get_next_timer_interrupt() called from |
| 1149 | * tick_nohz_next_event(). |
| 1150 | */ |
| 1151 | timer_clear_idle(); |
| 1152 | } |
| 1153 | |
| 1154 | /** |
| 1155 | * tick_nohz_idle_enter - prepare for entering idle on the current CPU |
| 1156 | * |
| 1157 | * Called when we start the idle loop. |
| 1158 | */ |
| 1159 | void tick_nohz_idle_enter(void) |
| 1160 | { |
| 1161 | struct tick_sched *ts; |
| 1162 | |
| 1163 | lockdep_assert_irqs_enabled(); |
| 1164 | |
| 1165 | local_irq_disable(); |
| 1166 | |
| 1167 | ts = this_cpu_ptr(&tick_cpu_sched); |
| 1168 | |
| 1169 | WARN_ON_ONCE(ts->timer_expires_base); |
| 1170 | |
| 1171 | ts->inidle = 1; |
| 1172 | tick_nohz_start_idle(ts); |
| 1173 | |
| 1174 | local_irq_enable(); |
| 1175 | } |
| 1176 | |
| 1177 | /** |
| 1178 | * tick_nohz_irq_exit - update next tick event from interrupt exit |
| 1179 | * |
| 1180 | * When an interrupt fires while we are idle and it doesn't cause |
| 1181 | * a reschedule, it may still add, modify or delete a timer, enqueue |
| 1182 | * an RCU callback, etc... |
| 1183 | * So we need to re-calculate and reprogram the next tick event. |
| 1184 | */ |
| 1185 | void tick_nohz_irq_exit(void) |
| 1186 | { |
| 1187 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1188 | |
| 1189 | if (ts->inidle) |
| 1190 | tick_nohz_start_idle(ts); |
| 1191 | else |
| 1192 | tick_nohz_full_update_tick(ts); |
| 1193 | } |
| 1194 | |
| 1195 | /** |
| 1196 | * tick_nohz_idle_got_tick - Check whether or not the tick handler has run |
| 1197 | */ |
| 1198 | bool tick_nohz_idle_got_tick(void) |
| 1199 | { |
| 1200 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1201 | |
| 1202 | if (ts->got_idle_tick) { |
| 1203 | ts->got_idle_tick = 0; |
| 1204 | return true; |
| 1205 | } |
| 1206 | return false; |
| 1207 | } |
| 1208 | |
| 1209 | /** |
| 1210 | * tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer |
| 1211 | * or the tick, whatever that expires first. Note that, if the tick has been |
| 1212 | * stopped, it returns the next hrtimer. |
| 1213 | * |
| 1214 | * Called from power state control code with interrupts disabled |
| 1215 | */ |
| 1216 | ktime_t tick_nohz_get_next_hrtimer(void) |
| 1217 | { |
| 1218 | return __this_cpu_read(tick_cpu_device.evtdev)->next_event; |
| 1219 | } |
| 1220 | |
| 1221 | /** |
| 1222 | * tick_nohz_get_sleep_length - return the expected length of the current sleep |
| 1223 | * @delta_next: duration until the next event if the tick cannot be stopped |
| 1224 | * |
| 1225 | * Called from power state control code with interrupts disabled. |
| 1226 | * |
| 1227 | * The return value of this function and/or the value returned by it through the |
| 1228 | * @delta_next pointer can be negative which must be taken into account by its |
| 1229 | * callers. |
| 1230 | */ |
| 1231 | ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next) |
| 1232 | { |
| 1233 | struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
| 1234 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1235 | int cpu = smp_processor_id(); |
| 1236 | /* |
| 1237 | * The idle entry time is expected to be a sufficient approximation of |
| 1238 | * the current time at this point. |
| 1239 | */ |
| 1240 | ktime_t now = ts->idle_entrytime; |
| 1241 | ktime_t next_event; |
| 1242 | |
| 1243 | WARN_ON_ONCE(!ts->inidle); |
| 1244 | |
| 1245 | *delta_next = ktime_sub(dev->next_event, now); |
| 1246 | |
| 1247 | if (!can_stop_idle_tick(cpu, ts)) |
| 1248 | return *delta_next; |
| 1249 | |
| 1250 | next_event = tick_nohz_next_event(ts, cpu); |
| 1251 | if (!next_event) |
| 1252 | return *delta_next; |
| 1253 | |
| 1254 | /* |
| 1255 | * If the next highres timer to expire is earlier than next_event, the |
| 1256 | * idle governor needs to know that. |
| 1257 | */ |
| 1258 | next_event = min_t(u64, next_event, |
| 1259 | hrtimer_next_event_without(&ts->sched_timer)); |
| 1260 | |
| 1261 | return ktime_sub(next_event, now); |
| 1262 | } |
| 1263 | |
| 1264 | /** |
| 1265 | * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value |
| 1266 | * for a particular CPU. |
| 1267 | * |
| 1268 | * Called from the schedutil frequency scaling governor in scheduler context. |
| 1269 | */ |
| 1270 | unsigned long tick_nohz_get_idle_calls_cpu(int cpu) |
| 1271 | { |
| 1272 | struct tick_sched *ts = tick_get_tick_sched(cpu); |
| 1273 | |
| 1274 | return ts->idle_calls; |
| 1275 | } |
| 1276 | |
| 1277 | /** |
| 1278 | * tick_nohz_get_idle_calls - return the current idle calls counter value |
| 1279 | * |
| 1280 | * Called from the schedutil frequency scaling governor in scheduler context. |
| 1281 | */ |
| 1282 | unsigned long tick_nohz_get_idle_calls(void) |
| 1283 | { |
| 1284 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1285 | |
| 1286 | return ts->idle_calls; |
| 1287 | } |
| 1288 | |
| 1289 | static void tick_nohz_account_idle_time(struct tick_sched *ts, |
| 1290 | ktime_t now) |
| 1291 | { |
| 1292 | unsigned long ticks; |
| 1293 | |
| 1294 | ts->idle_exittime = now; |
| 1295 | |
| 1296 | if (vtime_accounting_enabled_this_cpu()) |
| 1297 | return; |
| 1298 | /* |
| 1299 | * We stopped the tick in idle. Update process times would miss the |
| 1300 | * time we slept as update_process_times does only a 1 tick |
| 1301 | * accounting. Enforce that this is accounted to idle ! |
| 1302 | */ |
| 1303 | ticks = jiffies - ts->idle_jiffies; |
| 1304 | /* |
| 1305 | * We might be one off. Do not randomly account a huge number of ticks! |
| 1306 | */ |
| 1307 | if (ticks && ticks < LONG_MAX) |
| 1308 | account_idle_ticks(ticks); |
| 1309 | } |
| 1310 | |
| 1311 | void tick_nohz_idle_restart_tick(void) |
| 1312 | { |
| 1313 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1314 | |
| 1315 | if (ts->tick_stopped) { |
| 1316 | ktime_t now = ktime_get(); |
| 1317 | tick_nohz_restart_sched_tick(ts, now); |
| 1318 | tick_nohz_account_idle_time(ts, now); |
| 1319 | } |
| 1320 | } |
| 1321 | |
| 1322 | static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now) |
| 1323 | { |
| 1324 | if (tick_nohz_full_cpu(smp_processor_id())) |
| 1325 | __tick_nohz_full_update_tick(ts, now); |
| 1326 | else |
| 1327 | tick_nohz_restart_sched_tick(ts, now); |
| 1328 | |
| 1329 | tick_nohz_account_idle_time(ts, now); |
| 1330 | } |
| 1331 | |
| 1332 | /** |
| 1333 | * tick_nohz_idle_exit - restart the idle tick from the idle task |
| 1334 | * |
| 1335 | * Restart the idle tick when the CPU is woken up from idle |
| 1336 | * This also exit the RCU extended quiescent state. The CPU |
| 1337 | * can use RCU again after this function is called. |
| 1338 | */ |
| 1339 | void tick_nohz_idle_exit(void) |
| 1340 | { |
| 1341 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1342 | bool idle_active, tick_stopped; |
| 1343 | ktime_t now; |
| 1344 | |
| 1345 | local_irq_disable(); |
| 1346 | |
| 1347 | WARN_ON_ONCE(!ts->inidle); |
| 1348 | WARN_ON_ONCE(ts->timer_expires_base); |
| 1349 | |
| 1350 | ts->inidle = 0; |
| 1351 | idle_active = ts->idle_active; |
| 1352 | tick_stopped = ts->tick_stopped; |
| 1353 | |
| 1354 | if (idle_active || tick_stopped) |
| 1355 | now = ktime_get(); |
| 1356 | |
| 1357 | if (idle_active) |
| 1358 | tick_nohz_stop_idle(ts, now); |
| 1359 | |
| 1360 | if (tick_stopped) |
| 1361 | tick_nohz_idle_update_tick(ts, now); |
| 1362 | |
| 1363 | local_irq_enable(); |
| 1364 | } |
| 1365 | |
| 1366 | /* |
| 1367 | * The nohz low res interrupt handler |
| 1368 | */ |
| 1369 | static void tick_nohz_handler(struct clock_event_device *dev) |
| 1370 | { |
| 1371 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1372 | struct pt_regs *regs = get_irq_regs(); |
| 1373 | ktime_t now = ktime_get(); |
| 1374 | |
| 1375 | dev->next_event = KTIME_MAX; |
| 1376 | |
| 1377 | tick_sched_do_timer(ts, now); |
| 1378 | tick_sched_handle(ts, regs); |
| 1379 | |
| 1380 | if (unlikely(ts->tick_stopped)) { |
| 1381 | /* |
| 1382 | * The clockevent device is not reprogrammed, so change the |
| 1383 | * clock event device to ONESHOT_STOPPED to avoid spurious |
| 1384 | * interrupts on devices which might not be truly one shot. |
| 1385 | */ |
| 1386 | tick_program_event(KTIME_MAX, 1); |
| 1387 | return; |
| 1388 | } |
| 1389 | |
| 1390 | hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); |
| 1391 | tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); |
| 1392 | } |
| 1393 | |
| 1394 | static inline void tick_nohz_activate(struct tick_sched *ts, int mode) |
| 1395 | { |
| 1396 | if (!tick_nohz_enabled) |
| 1397 | return; |
| 1398 | ts->nohz_mode = mode; |
| 1399 | /* One update is enough */ |
| 1400 | if (!test_and_set_bit(0, &tick_nohz_active)) |
| 1401 | timers_update_nohz(); |
| 1402 | } |
| 1403 | |
| 1404 | /** |
| 1405 | * tick_nohz_switch_to_nohz - switch to nohz mode |
| 1406 | */ |
| 1407 | static void tick_nohz_switch_to_nohz(void) |
| 1408 | { |
| 1409 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1410 | ktime_t next; |
| 1411 | |
| 1412 | if (!tick_nohz_enabled) |
| 1413 | return; |
| 1414 | |
| 1415 | if (tick_switch_to_oneshot(tick_nohz_handler)) |
| 1416 | return; |
| 1417 | |
| 1418 | /* |
| 1419 | * Recycle the hrtimer in ts, so we can share the |
| 1420 | * hrtimer_forward with the highres code. |
| 1421 | */ |
| 1422 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); |
| 1423 | /* Get the next period */ |
| 1424 | next = tick_init_jiffy_update(); |
| 1425 | |
| 1426 | hrtimer_set_expires(&ts->sched_timer, next); |
| 1427 | hrtimer_forward_now(&ts->sched_timer, TICK_NSEC); |
| 1428 | tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1); |
| 1429 | tick_nohz_activate(ts, NOHZ_MODE_LOWRES); |
| 1430 | } |
| 1431 | |
| 1432 | static inline void tick_nohz_irq_enter(void) |
| 1433 | { |
| 1434 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1435 | ktime_t now; |
| 1436 | |
| 1437 | if (!ts->idle_active && !ts->tick_stopped) |
| 1438 | return; |
| 1439 | now = ktime_get(); |
| 1440 | if (ts->idle_active) |
| 1441 | tick_nohz_stop_idle(ts, now); |
| 1442 | /* |
| 1443 | * If all CPUs are idle. We may need to update a stale jiffies value. |
| 1444 | * Note nohz_full is a special case: a timekeeper is guaranteed to stay |
| 1445 | * alive but it might be busy looping with interrupts disabled in some |
| 1446 | * rare case (typically stop machine). So we must make sure we have a |
| 1447 | * last resort. |
| 1448 | */ |
| 1449 | if (ts->tick_stopped) |
| 1450 | tick_nohz_update_jiffies(now); |
| 1451 | } |
| 1452 | |
| 1453 | #else |
| 1454 | |
| 1455 | static inline void tick_nohz_switch_to_nohz(void) { } |
| 1456 | static inline void tick_nohz_irq_enter(void) { } |
| 1457 | static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { } |
| 1458 | |
| 1459 | #endif /* CONFIG_NO_HZ_COMMON */ |
| 1460 | |
| 1461 | /* |
| 1462 | * Called from irq_enter to notify about the possible interruption of idle() |
| 1463 | */ |
| 1464 | void tick_irq_enter(void) |
| 1465 | { |
| 1466 | tick_check_oneshot_broadcast_this_cpu(); |
| 1467 | tick_nohz_irq_enter(); |
| 1468 | } |
| 1469 | |
| 1470 | /* |
| 1471 | * High resolution timer specific code |
| 1472 | */ |
| 1473 | #ifdef CONFIG_HIGH_RES_TIMERS |
| 1474 | /* |
| 1475 | * We rearm the timer until we get disabled by the idle code. |
| 1476 | * Called with interrupts disabled. |
| 1477 | */ |
| 1478 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) |
| 1479 | { |
| 1480 | struct tick_sched *ts = |
| 1481 | container_of(timer, struct tick_sched, sched_timer); |
| 1482 | struct pt_regs *regs = get_irq_regs(); |
| 1483 | ktime_t now = ktime_get(); |
| 1484 | |
| 1485 | tick_sched_do_timer(ts, now); |
| 1486 | |
| 1487 | /* |
| 1488 | * Do not call, when we are not in irq context and have |
| 1489 | * no valid regs pointer |
| 1490 | */ |
| 1491 | if (regs) |
| 1492 | tick_sched_handle(ts, regs); |
| 1493 | else |
| 1494 | ts->next_tick = 0; |
| 1495 | |
| 1496 | /* No need to reprogram if we are in idle or full dynticks mode */ |
| 1497 | if (unlikely(ts->tick_stopped)) |
| 1498 | return HRTIMER_NORESTART; |
| 1499 | |
| 1500 | hrtimer_forward(timer, now, TICK_NSEC); |
| 1501 | |
| 1502 | return HRTIMER_RESTART; |
| 1503 | } |
| 1504 | |
| 1505 | static int sched_skew_tick; |
| 1506 | |
| 1507 | static int __init skew_tick(char *str) |
| 1508 | { |
| 1509 | get_option(&str, &sched_skew_tick); |
| 1510 | |
| 1511 | return 0; |
| 1512 | } |
| 1513 | early_param("skew_tick", skew_tick); |
| 1514 | |
| 1515 | /** |
| 1516 | * tick_setup_sched_timer - setup the tick emulation timer |
| 1517 | */ |
| 1518 | void tick_setup_sched_timer(void) |
| 1519 | { |
| 1520 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1521 | ktime_t now = ktime_get(); |
| 1522 | |
| 1523 | /* |
| 1524 | * Emulate tick processing via per-CPU hrtimers: |
| 1525 | */ |
| 1526 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD); |
| 1527 | ts->sched_timer.function = tick_sched_timer; |
| 1528 | |
| 1529 | /* Get the next period (per-CPU) */ |
| 1530 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
| 1531 | |
| 1532 | /* Offset the tick to avert jiffies_lock contention. */ |
| 1533 | if (sched_skew_tick) { |
| 1534 | u64 offset = TICK_NSEC >> 1; |
| 1535 | do_div(offset, num_possible_cpus()); |
| 1536 | offset *= smp_processor_id(); |
| 1537 | hrtimer_add_expires_ns(&ts->sched_timer, offset); |
| 1538 | } |
| 1539 | |
| 1540 | hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); |
| 1541 | hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD); |
| 1542 | tick_nohz_activate(ts, NOHZ_MODE_HIGHRES); |
| 1543 | } |
| 1544 | #endif /* HIGH_RES_TIMERS */ |
| 1545 | |
| 1546 | #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS |
| 1547 | void tick_cancel_sched_timer(int cpu) |
| 1548 | { |
| 1549 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); |
| 1550 | |
| 1551 | # ifdef CONFIG_HIGH_RES_TIMERS |
| 1552 | if (ts->sched_timer.base) |
| 1553 | hrtimer_cancel(&ts->sched_timer); |
| 1554 | # endif |
| 1555 | |
| 1556 | memset(ts, 0, sizeof(*ts)); |
| 1557 | } |
| 1558 | #endif |
| 1559 | |
| 1560 | /* |
| 1561 | * Async notification about clocksource changes |
| 1562 | */ |
| 1563 | void tick_clock_notify(void) |
| 1564 | { |
| 1565 | int cpu; |
| 1566 | |
| 1567 | for_each_possible_cpu(cpu) |
| 1568 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); |
| 1569 | } |
| 1570 | |
| 1571 | /* |
| 1572 | * Async notification about clock event changes |
| 1573 | */ |
| 1574 | void tick_oneshot_notify(void) |
| 1575 | { |
| 1576 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1577 | |
| 1578 | set_bit(0, &ts->check_clocks); |
| 1579 | } |
| 1580 | |
| 1581 | /* |
| 1582 | * Check, if a change happened, which makes oneshot possible. |
| 1583 | * |
| 1584 | * Called cyclic from the hrtimer softirq (driven by the timer |
| 1585 | * softirq) allow_nohz signals, that we can switch into low-res nohz |
| 1586 | * mode, because high resolution timers are disabled (either compile |
| 1587 | * or runtime). Called with interrupts disabled. |
| 1588 | */ |
| 1589 | int tick_check_oneshot_change(int allow_nohz) |
| 1590 | { |
| 1591 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
| 1592 | |
| 1593 | if (!test_and_clear_bit(0, &ts->check_clocks)) |
| 1594 | return 0; |
| 1595 | |
| 1596 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) |
| 1597 | return 0; |
| 1598 | |
| 1599 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
| 1600 | return 0; |
| 1601 | |
| 1602 | if (!allow_nohz) |
| 1603 | return 1; |
| 1604 | |
| 1605 | tick_nohz_switch_to_nohz(); |
| 1606 | return 0; |
| 1607 | } |