1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 *  Kernel internal schedule timeout and sleeping functions
  4 */
  5
  6#include <linux/delay.h>
  7#include <linux/jiffies.h>
  8#include <linux/timer.h>
  9#include <linux/sched/signal.h>
 10#include <linux/sched/debug.h>
 11
 12#include "tick-internal.h"
 13
 14/*
 15 * Since schedule_timeout()'s timer is defined on the stack, it must store
 16 * the target task on the stack as well.
 17 */
 18struct process_timer {
 19	struct timer_list timer;
 20	struct task_struct *task;
 21};
 22
 23static void process_timeout(struct timer_list *t)
 24{
 25	struct process_timer *timeout = from_timer(timeout, t, timer);
 26
 27	wake_up_process(timeout->task);
 28}
 29
 30/**
 31 * schedule_timeout - sleep until timeout
 32 * @timeout: timeout value in jiffies
 33 *
 34 * Make the current task sleep until @timeout jiffies have elapsed.
 35 * The function behavior depends on the current task state
 36 * (see also set_current_state() description):
 37 *
 38 * %TASK_RUNNING - the scheduler is called, but the task does not sleep
 39 * at all. That happens because sched_submit_work() does nothing for
 40 * tasks in %TASK_RUNNING state.
 41 *
 42 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
 43 * pass before the routine returns unless the current task is explicitly
 44 * woken up, (e.g. by wake_up_process()).
 45 *
 46 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
 47 * delivered to the current task or the current task is explicitly woken
 48 * up.
 49 *
 50 * The current task state is guaranteed to be %TASK_RUNNING when this
 51 * routine returns.
 52 *
 53 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
 54 * the CPU away without a bound on the timeout. In this case the return
 55 * value will be %MAX_SCHEDULE_TIMEOUT.
 56 *
 57 * Returns: 0 when the timer has expired otherwise the remaining time in
 58 * jiffies will be returned. In all cases the return value is guaranteed
 59 * to be non-negative.
 60 */
 61signed long __sched schedule_timeout(signed long timeout)
 62{
 63	struct process_timer timer;
 64	unsigned long expire;
 65
 66	switch (timeout) {
 67	case MAX_SCHEDULE_TIMEOUT:
 68		/*
 69		 * These two special cases are useful to be comfortable
 70		 * in the caller. Nothing more. We could take
 71		 * MAX_SCHEDULE_TIMEOUT from one of the negative value
 72		 * but I' d like to return a valid offset (>=0) to allow
 73		 * the caller to do everything it want with the retval.
 74		 */
 75		schedule();
 76		goto out;
 77	default:
 78		/*
 79		 * Another bit of PARANOID. Note that the retval will be
 80		 * 0 since no piece of kernel is supposed to do a check
 81		 * for a negative retval of schedule_timeout() (since it
 82		 * should never happens anyway). You just have the printk()
 83		 * that will tell you if something is gone wrong and where.
 84		 */
 85		if (timeout < 0) {
 86			pr_err("%s: wrong timeout value %lx\n", __func__, timeout);
 87			dump_stack();
 88			__set_current_state(TASK_RUNNING);
 89			goto out;
 90		}
 91	}
 92
 93	expire = timeout + jiffies;
 94
 95	timer.task = current;
 96	timer_setup_on_stack(&timer.timer, process_timeout, 0);
 97	timer.timer.expires = expire;
 98	add_timer(&timer.timer);
 99	schedule();
100	del_timer_sync(&timer.timer);
101
102	/* Remove the timer from the object tracker */
103	destroy_timer_on_stack(&timer.timer);
104
105	timeout = expire - jiffies;
106
107 out:
108	return timeout < 0 ? 0 : timeout;
109}
110EXPORT_SYMBOL(schedule_timeout);
111
112/*
113 * __set_current_state() can be used in schedule_timeout_*() functions, because
114 * schedule_timeout() calls schedule() unconditionally.
115 */
116
117/**
118 * schedule_timeout_interruptible - sleep until timeout (interruptible)
119 * @timeout: timeout value in jiffies
120 *
121 * See schedule_timeout() for details.
122 *
123 * Task state is set to TASK_INTERRUPTIBLE before starting the timeout.
124 */
125signed long __sched schedule_timeout_interruptible(signed long timeout)
126{
127	__set_current_state(TASK_INTERRUPTIBLE);
128	return schedule_timeout(timeout);
129}
130EXPORT_SYMBOL(schedule_timeout_interruptible);
131
132/**
133 * schedule_timeout_killable - sleep until timeout (killable)
134 * @timeout: timeout value in jiffies
135 *
136 * See schedule_timeout() for details.
137 *
138 * Task state is set to TASK_KILLABLE before starting the timeout.
139 */
140signed long __sched schedule_timeout_killable(signed long timeout)
141{
142	__set_current_state(TASK_KILLABLE);
143	return schedule_timeout(timeout);
144}
145EXPORT_SYMBOL(schedule_timeout_killable);
146
147/**
148 * schedule_timeout_uninterruptible - sleep until timeout (uninterruptible)
149 * @timeout: timeout value in jiffies
150 *
151 * See schedule_timeout() for details.
152 *
153 * Task state is set to TASK_UNINTERRUPTIBLE before starting the timeout.
154 */
155signed long __sched schedule_timeout_uninterruptible(signed long timeout)
156{
157	__set_current_state(TASK_UNINTERRUPTIBLE);
158	return schedule_timeout(timeout);
159}
160EXPORT_SYMBOL(schedule_timeout_uninterruptible);
161
162/**
163 * schedule_timeout_idle - sleep until timeout (idle)
164 * @timeout: timeout value in jiffies
165 *
166 * See schedule_timeout() for details.
167 *
168 * Task state is set to TASK_IDLE before starting the timeout. It is similar to
169 * schedule_timeout_uninterruptible(), except this task will not contribute to
170 * load average.
171 */
172signed long __sched schedule_timeout_idle(signed long timeout)
173{
174	__set_current_state(TASK_IDLE);
175	return schedule_timeout(timeout);
176}
177EXPORT_SYMBOL(schedule_timeout_idle);
178
179/**
180 * schedule_hrtimeout_range_clock - sleep until timeout
181 * @expires:	timeout value (ktime_t)
182 * @delta:	slack in expires timeout (ktime_t)
183 * @mode:	timer mode
184 * @clock_id:	timer clock to be used
185 *
186 * Details are explained in schedule_hrtimeout_range() function description as
187 * this function is commonly used.
188 */
189int __sched schedule_hrtimeout_range_clock(ktime_t *expires, u64 delta,
190					   const enum hrtimer_mode mode, clockid_t clock_id)
191{
192	struct hrtimer_sleeper t;
193
194	/*
195	 * Optimize when a zero timeout value is given. It does not
196	 * matter whether this is an absolute or a relative time.
197	 */
198	if (expires && *expires == 0) {
199		__set_current_state(TASK_RUNNING);
200		return 0;
201	}
202
203	/*
204	 * A NULL parameter means "infinite"
205	 */
206	if (!expires) {
207		schedule();
208		return -EINTR;
209	}
210
211	hrtimer_setup_sleeper_on_stack(&t, clock_id, mode);
212	hrtimer_set_expires_range_ns(&t.timer, *expires, delta);
213	hrtimer_sleeper_start_expires(&t, mode);
214
215	if (likely(t.task))
216		schedule();
217
218	hrtimer_cancel(&t.timer);
219	destroy_hrtimer_on_stack(&t.timer);
220
221	__set_current_state(TASK_RUNNING);
222
223	return !t.task ? 0 : -EINTR;
224}
225EXPORT_SYMBOL_GPL(schedule_hrtimeout_range_clock);
226
227/**
228 * schedule_hrtimeout_range - sleep until timeout
229 * @expires:	timeout value (ktime_t)
230 * @delta:	slack in expires timeout (ktime_t)
231 * @mode:	timer mode
232 *
233 * Make the current task sleep until the given expiry time has
234 * elapsed. The routine will return immediately unless
235 * the current task state has been set (see set_current_state()).
236 *
237 * The @delta argument gives the kernel the freedom to schedule the
238 * actual wakeup to a time that is both power and performance friendly
239 * for regular (non RT/DL) tasks.
240 * The kernel give the normal best effort behavior for "@expires+@delta",
241 * but may decide to fire the timer earlier, but no earlier than @expires.
242 *
243 * You can set the task state as follows -
244 *
245 * %TASK_UNINTERRUPTIBLE - at least @timeout time is guaranteed to
246 * pass before the routine returns unless the current task is explicitly
247 * woken up, (e.g. by wake_up_process()).
248 *
249 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
250 * delivered to the current task or the current task is explicitly woken
251 * up.
252 *
253 * The current task state is guaranteed to be TASK_RUNNING when this
254 * routine returns.
255 *
256 * Returns: 0 when the timer has expired. If the task was woken before the
257 * timer expired by a signal (only possible in state TASK_INTERRUPTIBLE) or
258 * by an explicit wakeup, it returns -EINTR.
259 */
260int __sched schedule_hrtimeout_range(ktime_t *expires, u64 delta,
261				     const enum hrtimer_mode mode)
262{
263	return schedule_hrtimeout_range_clock(expires, delta, mode,
264					      CLOCK_MONOTONIC);
265}
266EXPORT_SYMBOL_GPL(schedule_hrtimeout_range);
267
268/**
269 * schedule_hrtimeout - sleep until timeout
270 * @expires:	timeout value (ktime_t)
271 * @mode:	timer mode
272 *
273 * See schedule_hrtimeout_range() for details. @delta argument of
274 * schedule_hrtimeout_range() is set to 0 and has therefore no impact.
275 */
276int __sched schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode)
277{
278	return schedule_hrtimeout_range(expires, 0, mode);
279}
280EXPORT_SYMBOL_GPL(schedule_hrtimeout);
281
282/**
283 * msleep - sleep safely even with waitqueue interruptions
284 * @msecs:	Requested sleep duration in milliseconds
285 *
286 * msleep() uses jiffy based timeouts for the sleep duration. Because of the
287 * design of the timer wheel, the maximum additional percentage delay (slack) is
288 * 12.5%. This is only valid for timers which will end up in level 1 or a higher
289 * level of the timer wheel. For explanation of those 12.5% please check the
290 * detailed description about the basics of the timer wheel.
291 *
292 * The slack of timers which will end up in level 0 depends on sleep duration
293 * (msecs) and HZ configuration and can be calculated in the following way (with
294 * the timer wheel design restriction that the slack is not less than 12.5%):
295 *
296 *   ``slack = MSECS_PER_TICK / msecs``
297 *
298 * When the allowed slack of the callsite is known, the calculation could be
299 * turned around to find the minimal allowed sleep duration to meet the
300 * constraints. For example:
301 *
302 * * ``HZ=1000`` with ``slack=25%``: ``MSECS_PER_TICK / slack = 1 / (1/4) = 4``:
303 *   all sleep durations greater or equal 4ms will meet the constraints.
304 * * ``HZ=1000`` with ``slack=12.5%``: ``MSECS_PER_TICK / slack = 1 / (1/8) = 8``:
305 *   all sleep durations greater or equal 8ms will meet the constraints.
306 * * ``HZ=250`` with ``slack=25%``: ``MSECS_PER_TICK / slack = 4 / (1/4) = 16``:
307 *   all sleep durations greater or equal 16ms will meet the constraints.
308 * * ``HZ=250`` with ``slack=12.5%``: ``MSECS_PER_TICK / slack = 4 / (1/8) = 32``:
309 *   all sleep durations greater or equal 32ms will meet the constraints.
310 *
311 * See also the signal aware variant msleep_interruptible().
312 */
313void msleep(unsigned int msecs)
314{
315	unsigned long timeout = msecs_to_jiffies(msecs);
316
317	while (timeout)
318		timeout = schedule_timeout_uninterruptible(timeout);
319}
320EXPORT_SYMBOL(msleep);
321
322/**
323 * msleep_interruptible - sleep waiting for signals
324 * @msecs:	Requested sleep duration in milliseconds
325 *
326 * See msleep() for some basic information.
327 *
328 * The difference between msleep() and msleep_interruptible() is that the sleep
329 * could be interrupted by a signal delivery and then returns early.
330 *
331 * Returns: The remaining time of the sleep duration transformed to msecs (see
332 * schedule_timeout() for details).
333 */
334unsigned long msleep_interruptible(unsigned int msecs)
335{
336	unsigned long timeout = msecs_to_jiffies(msecs);
337
338	while (timeout && !signal_pending(current))
339		timeout = schedule_timeout_interruptible(timeout);
340	return jiffies_to_msecs(timeout);
341}
342EXPORT_SYMBOL(msleep_interruptible);
343
344/**
345 * usleep_range_state - Sleep for an approximate time in a given state
346 * @min:	Minimum time in usecs to sleep
347 * @max:	Maximum time in usecs to sleep
348 * @state:	State of the current task that will be while sleeping
349 *
350 * usleep_range_state() sleeps at least for the minimum specified time but not
351 * longer than the maximum specified amount of time. The range might reduce
352 * power usage by allowing hrtimers to coalesce an already scheduled interrupt
353 * with this hrtimer. In the worst case, an interrupt is scheduled for the upper
354 * bound.
355 *
356 * The sleeping task is set to the specified state before starting the sleep.
357 *
358 * In non-atomic context where the exact wakeup time is flexible, use
359 * usleep_range() or its variants instead of udelay(). The sleep improves
360 * responsiveness by avoiding the CPU-hogging busy-wait of udelay().
361 */
362void __sched usleep_range_state(unsigned long min, unsigned long max, unsigned int state)
363{
364	ktime_t exp = ktime_add_us(ktime_get(), min);
365	u64 delta = (u64)(max - min) * NSEC_PER_USEC;
366
367	if (WARN_ON_ONCE(max < min))
368		delta = 0;
369
370	for (;;) {
371		__set_current_state(state);
372		/* Do not return before the requested sleep time has elapsed */
373		if (!schedule_hrtimeout_range(&exp, delta, HRTIMER_MODE_ABS))
374			break;
375	}
376}
377EXPORT_SYMBOL(usleep_range_state);