aboutsummaryrefslogblamecommitdiffstats
path: root/mm/pagewalk.c
blob: d5878bed78412542b82c03022756db62c9d73d63 (plain) (tree) 
e6473092bd91





2165009bdf63

e6473092bd91





556637cdabcd

2165009bdf63

e6473092bd91


556637cdabcd





e6473092bd91






2165009bdf63

e6473092bd91










2165009bdf63

e6473092bd91





2165009bdf63

e6473092bd91

2165009bdf63

e6473092bd91








2165009bdf63

e6473092bd91










2165009bdf63

e6473092bd91





2165009bdf63

e6473092bd91

2165009bdf63

e6473092bd91









7682486b3ee0




e6473092bd91






2165009bdf63



e6473092bd91







2165009bdf63


e6473092bd91








2165009bdf63




e6473092bd91




2165009bdf63

e6473092bd91





2165009bdf63

e6473092bd91


2165009bdf63

e6473092bd91






1
2
3
4
5

6

7
8
9
10
11

12

13

14
15

16
17
18
19
20

21
22
23
24
25
26

27

28
29
30
31
32
33
34
35
36
37

38

39
40
41
42
43

44

45

46

47
48
49
50
51
52
53
54

55

56
57
58
59
60
61
62
63
64
65

66

67
68
69
70
71

72

73

74

75
76
77
78
79
80
81
82
83

84
85
86
87

88
89
90
91
92
93

94
95
96

97
98
99
100
101
102
103

104
105

106
107
108
109
110
111
112
113

114
115
116
117

118
119
120
121

122

123
124
125
126
127

128

129
130

131

132
133
134
135
136
137





                                                                            
                                               




                                        
                  
                                                                         

                             




                                  





                                                                            
                                               









                                                 
                                                                       




                                      
                                                                     
                                            
                                                                    







                                                                            
                                               









                                                 
                                                                       




                                      
                                                                     
                                                                 
                                                                    








                                                                    



                                                               





                                                                         


                                                                       






                                                                              

                                                          







                           



                                         



                                                 
                                                                       




                                      
                                                                     

                                                                            
                                                                    





                                                  
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/sched.h>

static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
			  struct mm_walk *walk)
{
	pte_t *pte;
	int err = 0;

	pte = pte_offset_map(pmd, addr);
	for (;;) {
		err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
		if (err)
		       break;
		addr += PAGE_SIZE;
		if (addr == end)
			break;
		pte++;
	}

	pte_unmap(pte);
	return err;
}

static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
			  struct mm_walk *walk)
{
	pmd_t *pmd;
	unsigned long next;
	int err = 0;

	pmd = pmd_offset(pud, addr);
	do {
		next = pmd_addr_end(addr, end);
		if (pmd_none_or_clear_bad(pmd)) {
			if (walk->pte_hole)
				err = walk->pte_hole(addr, next, walk);
			if (err)
				break;
			continue;
		}
		if (walk->pmd_entry)
			err = walk->pmd_entry(pmd, addr, next, walk);
		if (!err && walk->pte_entry)
			err = walk_pte_range(pmd, addr, next, walk);
		if (err)
			break;
	} while (pmd++, addr = next, addr != end);

	return err;
}

static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
			  struct mm_walk *walk)
{
	pud_t *pud;
	unsigned long next;
	int err = 0;

	pud = pud_offset(pgd, addr);
	do {
		next = pud_addr_end(addr, end);
		if (pud_none_or_clear_bad(pud)) {
			if (walk->pte_hole)
				err = walk->pte_hole(addr, next, walk);
			if (err)
				break;
			continue;
		}
		if (walk->pud_entry)
			err = walk->pud_entry(pud, addr, next, walk);
		if (!err && (walk->pmd_entry || walk->pte_entry))
			err = walk_pmd_range(pud, addr, next, walk);
		if (err)
			break;
	} while (pud++, addr = next, addr != end);

	return err;
}

/**
 * walk_page_range - walk a memory map's page tables with a callback
 * @mm: memory map to walk
 * @addr: starting address
 * @end: ending address
 * @walk: set of callbacks to invoke for each level of the tree
 *
 * Recursively walk the page table for the memory area in a VMA,
 * calling supplied callbacks. Callbacks are called in-order (first
 * PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
 * etc.). If lower-level callbacks are omitted, walking depth is reduced.
 *
 * Each callback receives an entry pointer and the start and end of the
 * associated range, and a copy of the original mm_walk for access to
 * the ->private or ->mm fields.
 *
 * No locks are taken, but the bottom level iterator will map PTE
 * directories from highmem if necessary.
 *
 * If any callback returns a non-zero value, the walk is aborted and
 * the return value is propagated back to the caller. Otherwise 0 is returned.
 */
int walk_page_range(unsigned long addr, unsigned long end,
		    struct mm_walk *walk)
{
	pgd_t *pgd;
	unsigned long next;
	int err = 0;

	if (addr >= end)
		return err;

	if (!walk->mm)
		return -EINVAL;

	pgd = pgd_offset(walk->mm, addr);
	do {
		next = pgd_addr_end(addr, end);
		if (pgd_none_or_clear_bad(pgd)) {
			if (walk->pte_hole)
				err = walk->pte_hole(addr, next, walk);
			if (err)
				break;
			continue;
		}
		if (walk->pgd_entry)
			err = walk->pgd_entry(pgd, addr, next, walk);
		if (!err &&
		    (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
			err = walk_pud_range(pgd, addr, next, walk);
		if (err)
			break;
	} while (pgd++, addr = next, addr != end);

	return err;
}
generated by cgit v1.2.2 (git 2.25.0) at 2025-02-06 12:11:12 -0500
='n1322' href='#n1322'>1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 
/*
 * Implement CPU time clocks for the POSIX clock interface.
 */

#include <linux/sched.h>
#include <linux/posix-timers.h>
#include <asm/uaccess.h>
#include <linux/errno.h>

static int check_clock(const clockid_t which_clock)
{
	int error = 0;
	struct task_struct *p;
	const pid_t pid = CPUCLOCK_PID(which_clock);

	if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
		return -EINVAL;

	if (pid == 0)
		return 0;

	read_lock(&tasklist_lock);
	p = find_task_by_vpid(pid);
	if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
		   same_thread_group(p, current) : thread_group_leader(p))) {
		error = -EINVAL;
	}
	read_unlock(&tasklist_lock);

	return error;
}

static inline union cpu_time_count
timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
{
	union cpu_time_count ret;
	ret.sched = 0;		/* high half always zero when .cpu used */
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
	} else {
		ret.cpu = timespec_to_cputime(tp);
	}
	return ret;
}

static void sample_to_timespec(const clockid_t which_clock,
			       union cpu_time_count cpu,
			       struct timespec *tp)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		tp->tv_sec = div_long_long_rem(cpu.sched,
					       NSEC_PER_SEC, &tp->tv_nsec);
	} else {
		cputime_to_timespec(cpu.cpu, tp);
	}
}

static inline int cpu_time_before(const clockid_t which_clock,
				  union cpu_time_count now,
				  union cpu_time_count then)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		return now.sched < then.sched;
	}  else {
		return cputime_lt(now.cpu, then.cpu);
	}
}
static inline void cpu_time_add(const clockid_t which_clock,
				union cpu_time_count *acc,
			        union cpu_time_count val)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		acc->sched += val.sched;
	}  else {
		acc->cpu = cputime_add(acc->cpu, val.cpu);
	}
}
static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
						union cpu_time_count a,
						union cpu_time_count b)
{
	if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
		a.sched -= b.sched;
	}  else {
		a.cpu = cputime_sub(a.cpu, b.cpu);
	}
	return a;
}

/*
 * Divide and limit the result to res >= 1
 *
 * This is necessary to prevent signal delivery starvation, when the result of
 * the division would be rounded down to 0.
 */
static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
{
	cputime_t res = cputime_div(time, div);

	return max_t(cputime_t, res, 1);
}

/*
 * Update expiry time from increment, and increase overrun count,
 * given the current clock sample.
 */
static void bump_cpu_timer(struct k_itimer *timer,
				  union cpu_time_count now)
{
	int i;

	if (timer->it.cpu.incr.sched == 0)
		return;

	if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
		unsigned long long delta, incr;

		if (now.sched < timer->it.cpu.expires.sched)
			return;
		incr = timer->it.cpu.incr.sched;
		delta = now.sched + incr - timer->it.cpu.expires.sched;
		/* Don't use (incr*2 < delta), incr*2 might overflow. */
		for (i = 0; incr < delta - incr; i++)
			incr = incr << 1;
		for (; i >= 0; incr >>= 1, i--) {
			if (delta < incr)
				continue;
			timer->it.cpu.expires.sched += incr;
			timer->it_overrun += 1 << i;
			delta -= incr;
		}
	} else {
		cputime_t delta, incr;

		if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
			return;
		incr = timer->it.cpu.incr.cpu;
		delta = cputime_sub(cputime_add(now.cpu, incr),
				    timer->it.cpu.expires.cpu);
		/* Don't use (incr*2 < delta), incr*2 might overflow. */
		for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
			     incr = cputime_add(incr, incr);
		for (; i >= 0; incr = cputime_halve(incr), i--) {
			if (cputime_lt(delta, incr))
				continue;
			timer->it.cpu.expires.cpu =
				cputime_add(timer->it.cpu.expires.cpu, incr);
			timer->it_overrun += 1 << i;
			delta = cputime_sub(delta, incr);
		}
	}
}

static inline cputime_t prof_ticks(struct task_struct *p)
{
	return cputime_add(p->utime, p->stime);
}
static inline cputime_t virt_ticks(struct task_struct *p)
{
	return p->utime;
}
static inline unsigned long long sched_ns(struct task_struct *p)
{
	return task_sched_runtime(p);
}

int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
	int error = check_clock(which_clock);
	if (!error) {
		tp->tv_sec = 0;
		tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
		if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
			/*
			 * If sched_clock is using a cycle counter, we
			 * don't have any idea of its true resolution
			 * exported, but it is much more than 1s/HZ.
			 */
			tp->tv_nsec = 1;
		}
	}
	return error;
}

int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
{
	/*
	 * You can never reset a CPU clock, but we check for other errors
	 * in the call before failing with EPERM.
	 */
	int error = check_clock(which_clock);
	if (error == 0) {
		error = -EPERM;
	}
	return error;
}


/*
 * Sample a per-thread clock for the given task.
 */
static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
			    union cpu_time_count *cpu)
{
	switch (CPUCLOCK_WHICH(which_clock)) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		cpu->cpu = prof_ticks(p);
		break;
	case CPUCLOCK_VIRT:
		cpu->cpu = virt_ticks(p);
		break;
	case CPUCLOCK_SCHED:
		cpu->sched = sched_ns(p);
		break;
	}
	return 0;
}

/*
 * Sample a process (thread group) clock for the given group_leader task.
 * Must be called with tasklist_lock held for reading.
 * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
 */
static int cpu_clock_sample_group_locked(unsigned int clock_idx,
					 struct task_struct *p,
					 union cpu_time_count *cpu)
{
	struct task_struct *t = p;
 	switch (clock_idx) {
	default:
		return -EINVAL;
	case CPUCLOCK_PROF:
		cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
		do {
			cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
			t = next_thread(t);
		} while (t != p);
		break;
	case CPUCLOCK_VIRT:
		cpu->cpu = p->signal->utime;
		do {
			cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
			t = next_thread(t);
		} while (t != p);
		break;
	case CPUCLOCK_SCHED:
		cpu->sched = p->signal->sum_sched_runtime;
		/* Add in each other live thread.  */
		while ((t = next_thread(t)) != p) {
			cpu->sched += t->se.sum_exec_runtime;
		}
		cpu->sched += sched_ns(p);
		break;
	}
	return 0;
}

/*
 * Sample a process (thread group) clock for the given group_leader task.
 * Must be called with tasklist_lock held for reading.
 */
static int cpu_clock_sample_group(const clockid_t which_clock,
				  struct task_struct *p,
				  union cpu_time_count *cpu)
{
	int ret;
	unsigned long flags;
	spin_lock_irqsave(&p->sighand->siglock, flags);
	ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
					    cpu);
	spin_unlock_irqrestore(&p->sighand->siglock, flags);
	return ret;
}


int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
	const pid_t pid = CPUCLOCK_PID(which_clock);
	int error = -EINVAL;
	union cpu_time_count rtn;

	if (pid == 0) {
		/*
		 * Special case constant value for our own clocks.
		 * We don't have to do any lookup to find ourselves.
		 */
		if (CPUCLOCK_PERTHREAD(which_clock)) {
			/*
			 * Sampling just ourselves we can do with no locking.
			 */
			error = cpu_clock_sample(which_clock,
						 current, &rtn);
		} else {
			read_lock(&tasklist_lock);
			error = cpu_clock_sample_group(which_clock,
						       current, &rtn);
			read_unlock(&tasklist_lock);
		}
	} else {
		/*
		 * Find the given PID, and validate that the caller
		 * should be able to see it.
		 */
		struct task_struct *p;
		rcu_read_lock();
		p = find_task_by_vpid(pid);
		if (p) {
			if (CPUCLOCK_PERTHREAD(which_clock)) {
				if (same_thread_group(p, current)) {
					error = cpu_clock_sample(which_clock,
								 p, &rtn);
				}
			} else {
				read_lock(&tasklist_lock);
				if (thread_group_leader(p) && p->signal) {
					error =
					    cpu_clock_sample_group(which_clock,
							           p, &rtn);
				}
				read_unlock(&tasklist_lock);
			}
		}
		rcu_read_unlock();
	}

	if (error)
		return error;
	sample_to_timespec(which_clock, rtn, tp);
	return 0;
}


/*
 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 * This is called from sys_timer_create with the new timer already locked.
 */
int posix_cpu_timer_create(struct k_itimer *new_timer)
{
	int ret = 0;
	const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
	struct task_struct *p;

	if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
		return -EINVAL;

	INIT_LIST_HEAD(&new_timer->it.cpu.entry);
	new_timer->it.cpu.incr.sched = 0;
	new_timer->it.cpu.expires.sched = 0;

	read_lock(&tasklist_lock);
	if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
		if (pid == 0) {
			p = current;
		} else {
			p = find_task_by_vpid(pid);
			if (p && !same_thread_group(p, current))
				p = NULL;
		}
	} else {
		if (pid == 0) {
			p = current->group_leader;
		} else {
			p = find_task_by_vpid(pid);
			if (p && !thread_group_leader(p))
				p = NULL;
		}
	}
	new_timer->it.cpu.task = p;
	if (p) {
		get_task_struct(p);
	} else {
		ret = -EINVAL;
	}
	read_unlock(&tasklist_lock);

	return ret;
}

/*
 * Clean up a CPU-clock timer that is about to be destroyed.
 * This is called from timer deletion with the timer already locked.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
int posix_cpu_timer_del(struct k_itimer *timer)
{
	struct task_struct *p = timer->it.cpu.task;
	int ret = 0;

	if (likely(p != NULL)) {
		read_lock(&tasklist_lock);
		if (unlikely(p->signal == NULL)) {
			/*
			 * We raced with the reaping of the task.
			 * The deletion should have cleared us off the list.
			 */
			BUG_ON(!list_empty(&timer->it.cpu.entry));
		} else {
			spin_lock(&p->sighand->siglock);
			if (timer->it.cpu.firing)
				ret = TIMER_RETRY;
			else
				list_del(&timer->it.cpu.entry);
			spin_unlock(&p->sighand->siglock);
		}
		read_unlock(&tasklist_lock);

		if (!ret)
			put_task_struct(p);
	}

	return ret;
}

/*
 * Clean out CPU timers still ticking when a thread exited.  The task
 * pointer is cleared, and the expiry time is replaced with the residual
 * time for later timer_gettime calls to return.
 * This must be called with the siglock held.
 */
static void cleanup_timers(struct list_head *head,
			   cputime_t utime, cputime_t stime,
			   unsigned long long sum_exec_runtime)
{
	struct cpu_timer_list *timer, *next;
	cputime_t ptime = cputime_add(utime, stime);

	list_for_each_entry_safe(timer, next, head, entry) {
		list_del_init(&timer->entry);
		if (cputime_lt(timer->expires.cpu, ptime)) {
			timer->expires.cpu = cputime_zero;
		} else {
			timer->expires.cpu = cputime_sub(timer->expires.cpu,
							 ptime);
		}
	}

	++head;
	list_for_each_entry_safe(timer, next, head, entry) {
		list_del_init(&timer->entry);
		if (cputime_lt(timer->expires.cpu, utime)) {
			timer->expires.cpu = cputime_zero;
		} else {
			timer->expires.cpu = cputime_sub(timer->expires.cpu,
							 utime);
		}
	}

	++head;
	list_for_each_entry_safe(timer, next, head, entry) {
		list_del_init(&timer->entry);
		if (timer->expires.sched < sum_exec_runtime) {
			timer->expires.sched = 0;
		} else {
			timer->expires.sched -= sum_exec_runtime;
		}
	}
}

/*
 * These are both called with the siglock held, when the current thread
 * is being reaped.  When the final (leader) thread in the group is reaped,
 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 */
void posix_cpu_timers_exit(struct task_struct *tsk)
{
	cleanup_timers(tsk->cpu_timers,
		       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);

}
void posix_cpu_timers_exit_group(struct task_struct *tsk)
{
	cleanup_timers(tsk->signal->cpu_timers,
		       cputime_add(tsk->utime, tsk->signal->utime),
		       cputime_add(tsk->stime, tsk->signal->stime),
		     tsk->se.sum_exec_runtime + tsk->signal->sum_sched_runtime);
}


/*
 * Set the expiry times of all the threads in the process so one of them
 * will go off before the process cumulative expiry total is reached.
 */
static void process_timer_rebalance(struct task_struct *p,
				    unsigned int clock_idx,
				    union cpu_time_count expires,
				    union cpu_time_count val)
{
	cputime_t ticks, left;
	unsigned long long ns, nsleft;
 	struct task_struct *t = p;
	unsigned int nthreads = atomic_read(&p->signal->live);

	if (!nthreads)
		return;

	switch (clock_idx) {
	default:
		BUG();
		break;
	case CPUCLOCK_PROF:
		left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
				       nthreads);
		do {
			if (likely(!(t->flags & PF_EXITING))) {
				ticks = cputime_add(prof_ticks(t), left);
				if (cputime_eq(t->it_prof_expires,
					       cputime_zero) ||
				    cputime_gt(t->it_prof_expires, ticks)) {
					t->it_prof_expires = ticks;
				}
			}
			t = next_thread(t);
		} while (t != p);
		break;
	case CPUCLOCK_VIRT:
		left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
				       nthreads);
		do {
			if (likely(!(t->flags & PF_EXITING))) {
				ticks = cputime_add(virt_ticks(t), left);
				if (cputime_eq(t->it_virt_expires,
					       cputime_zero) ||
				    cputime_gt(t->it_virt_expires, ticks)) {
					t->it_virt_expires = ticks;
				}
			}
			t = next_thread(t);
		} while (t != p);
		break;
	case CPUCLOCK_SCHED:
		nsleft = expires.sched - val.sched;
		do_div(nsleft, nthreads);
		nsleft = max_t(unsigned long long, nsleft, 1);
		do {
			if (likely(!(t->flags & PF_EXITING))) {
				ns = t->se.sum_exec_runtime + nsleft;
				if (t->it_sched_expires == 0 ||
				    t->it_sched_expires > ns) {
					t->it_sched_expires = ns;
				}
			}
			t = next_thread(t);
		} while (t != p);
		break;
	}
}

static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
{
	/*
	 * That's all for this thread or process.
	 * We leave our residual in expires to be reported.
	 */
	put_task_struct(timer->it.cpu.task);
	timer->it.cpu.task = NULL;
	timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
					     timer->it.cpu.expires,
					     now);
}

/*
 * Insert the timer on the appropriate list before any timers that
 * expire later.  This must be called with the tasklist_lock held
 * for reading, and interrupts disabled.
 */
static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
{
	struct task_struct *p = timer->it.cpu.task;
	struct list_head *head, *listpos;
	struct cpu_timer_list *const nt = &timer->it.cpu;
	struct cpu_timer_list *next;
	unsigned long i;

	head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
		p->cpu_timers : p->signal->cpu_timers);
	head += CPUCLOCK_WHICH(timer->it_clock);

	BUG_ON(!irqs_disabled());
	spin_lock(&p->sighand->siglock);

	listpos = head;
	if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
		list_for_each_entry(next, head, entry) {
			if (next->expires.sched > nt->expires.sched)
				break;
			listpos = &next->entry;
		}
	} else {
		list_for_each_entry(next, head, entry) {
			if (cputime_gt(next->expires.cpu, nt->expires.cpu))
				break;
			listpos = &next->entry;
		}
	}
	list_add(&nt->entry, listpos);

	if (listpos == head) {
		/*
		 * We are the new earliest-expiring timer.
		 * If we are a thread timer, there can always
		 * be a process timer telling us to stop earlier.
		 */

		if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
			switch (CPUCLOCK_WHICH(timer->it_clock)) {
			default:
				BUG();
			case CPUCLOCK_PROF:
				if (cputime_eq(p->it_prof_expires,
					       cputime_zero) ||
				    cputime_gt(p->it_prof_expires,
					       nt->expires.cpu))
					p->it_prof_expires = nt->expires.cpu;
				break;
			case CPUCLOCK_VIRT:
				if (cputime_eq(p->it_virt_expires,
					       cputime_zero) ||
				    cputime_gt(p->it_virt_expires,
					       nt->expires.cpu))
					p->it_virt_expires = nt->expires.cpu;
				break;
			case CPUCLOCK_SCHED:
				if (p->it_sched_expires == 0 ||
				    p->it_sched_expires > nt->expires.sched)
					p->it_sched_expires = nt->expires.sched;
				break;
			}
		} else {
			/*
			 * For a process timer, we must balance
			 * all the live threads' expirations.
			 */
			switch (CPUCLOCK_WHICH(timer->it_clock)) {
			default:
				BUG();
			case CPUCLOCK_VIRT:
				if (!cputime_eq(p->signal->it_virt_expires,
						cputime_zero) &&
				    cputime_lt(p->signal->it_virt_expires,
					       timer->it.cpu.expires.cpu))
					break;
				goto rebalance;
			case CPUCLOCK_PROF:
				if (!cputime_eq(p->signal->it_prof_expires,
						cputime_zero) &&
				    cputime_lt(p->signal->it_prof_expires,
					       timer->it.cpu.expires.cpu))
					break;
				i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
				if (i != RLIM_INFINITY &&
				    i <= cputime_to_secs(timer->it.cpu.expires.cpu))
					break;
				goto rebalance;
			case CPUCLOCK_SCHED:
			rebalance:
				process_timer_rebalance(
					timer->it.cpu.task,
					CPUCLOCK_WHICH(timer->it_clock),
					timer->it.cpu.expires, now);
				break;
			}
		}
	}

	spin_unlock(&p->sighand->siglock);
}

/*
 * The timer is locked, fire it and arrange for its reload.
 */
static void cpu_timer_fire(struct k_itimer *timer)
{
	if (unlikely(timer->sigq == NULL)) {
		/*
		 * This a special case for clock_nanosleep,
		 * not a normal timer from sys_timer_create.
		 */
		wake_up_process(timer->it_process);
		timer->it.cpu.expires.sched = 0;
	} else if (timer->it.cpu.incr.sched == 0) {
		/*
		 * One-shot timer.  Clear it as soon as it's fired.
		 */
		posix_timer_event(timer, 0);
		timer->it.cpu.expires.sched = 0;
	} else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
		/*
		 * The signal did not get queued because the signal
		 * was ignored, so we won't get any callback to
		 * reload the timer.  But we need to keep it
		 * ticking in case the signal is deliverable next time.
		 */
		posix_cpu_timer_schedule(timer);
	}
}

/*
 * Guts of sys_timer_settime for CPU timers.
 * This is called with the timer locked and interrupts disabled.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
int posix_cpu_timer_set(struct k_itimer *timer, int flags,
			struct itimerspec *new, struct itimerspec *old)
{
	struct task_struct *p = timer->it.cpu.task;
	union cpu_time_count old_expires, new_expires, val;
	int ret;

	if (unlikely(p == NULL)) {
		/*
		 * Timer refers to a dead task's clock.
		 */
		return -ESRCH;
	}

	new_expires = timespec_to_sample(timer->it_clock, &new->it_value);

	read_lock(&tasklist_lock);
	/*
	 * We need the tasklist_lock to protect against reaping that
	 * clears p->signal.  If p has just been reaped, we can no
	 * longer get any information about it at all.
	 */
	if (unlikely(p->signal == NULL)) {
		read_unlock(&tasklist_lock);
		put_task_struct(p);
		timer->it.cpu.task = NULL;
		return -ESRCH;
	}

	/*
	 * Disarm any old timer after extracting its expiry time.
	 */
	BUG_ON(!irqs_disabled());

	ret = 0;
	spin_lock(&p->sighand->siglock);
	old_expires = timer->it.cpu.expires;
	if (unlikely(timer->it.cpu.firing)) {
		timer->it.cpu.firing = -1;
		ret = TIMER_RETRY;
	} else
		list_del_init(&timer->it.cpu.entry);
	spin_unlock(&p->sighand->siglock);

	/*
	 * We need to sample the current value to convert the new
	 * value from to relative and absolute, and to convert the
	 * old value from absolute to relative.  To set a process
	 * timer, we need a sample to balance the thread expiry
	 * times (in arm_timer).  With an absolute time, we must
	 * check if it's already passed.  In short, we need a sample.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &val);
	} else {
		cpu_clock_sample_group(timer->it_clock, p, &val);
	}

	if (old) {
		if (old_expires.sched == 0) {
			old->it_value.tv_sec = 0;
			old->it_value.tv_nsec = 0;
		} else {
			/*
			 * Update the timer in case it has
			 * overrun already.  If it has,
			 * we'll report it as having overrun
			 * and with the next reloaded timer
			 * already ticking, though we are
			 * swallowing that pending
			 * notification here to install the
			 * new setting.
			 */
			bump_cpu_timer(timer, val);
			if (cpu_time_before(timer->it_clock, val,
					    timer->it.cpu.expires)) {
				old_expires = cpu_time_sub(
					timer->it_clock,
					timer->it.cpu.expires, val);
				sample_to_timespec(timer->it_clock,
						   old_expires,
						   &old->it_value);
			} else {
				old->it_value.tv_nsec = 1;
				old->it_value.tv_sec = 0;
			}
		}
	}

	if (unlikely(ret)) {
		/*
		 * We are colliding with the timer actually firing.
		 * Punt after filling in the timer's old value, and
		 * disable this firing since we are already reporting
		 * it as an overrun (thanks to bump_cpu_timer above).
		 */
		read_unlock(&tasklist_lock);
		goto out;
	}

	if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
		cpu_time_add(timer->it_clock, &new_expires, val);
	}

	/*
	 * Install the new expiry time (or zero).
	 * For a timer with no notification action, we don't actually
	 * arm the timer (we'll just fake it for timer_gettime).
	 */
	timer->it.cpu.expires = new_expires;
	if (new_expires.sched != 0 &&
	    (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
	    cpu_time_before(timer->it_clock, val, new_expires)) {
		arm_timer(timer, val);
	}

	read_unlock(&tasklist_lock);

	/*
	 * Install the new reload setting, and
	 * set up the signal and overrun bookkeeping.
	 */
	timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
						&new->it_interval);

	/*
	 * This acts as a modification timestamp for the timer,
	 * so any automatic reload attempt will punt on seeing
	 * that we have reset the timer manually.
	 */
	timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
		~REQUEUE_PENDING;
	timer->it_overrun_last = 0;
	timer->it_overrun = -1;

	if (new_expires.sched != 0 &&
	    (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
	    !cpu_time_before(timer->it_clock, val, new_expires)) {
		/*
		 * The designated time already passed, so we notify
		 * immediately, even if the thread never runs to
		 * accumulate more time on this clock.
		 */
		cpu_timer_fire(timer);
	}

	ret = 0;
 out:
	if (old) {
		sample_to_timespec(timer->it_clock,
				   timer->it.cpu.incr, &old->it_interval);
	}
	return ret;
}

void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
{
	union cpu_time_count now;
	struct task_struct *p = timer->it.cpu.task;
	int clear_dead;

	/*
	 * Easy part: convert the reload time.
	 */
	sample_to_timespec(timer->it_clock,
			   timer->it.cpu.incr, &itp->it_interval);

	if (timer->it.cpu.expires.sched == 0) {	/* Timer not armed at all.  */
		itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
		return;
	}

	if (unlikely(p == NULL)) {
		/*
		 * This task already died and the timer will never fire.
		 * In this case, expires is actually the dead value.
		 */
	dead:
		sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
				   &itp->it_value);
		return;
	}

	/*
	 * Sample the clock to take the difference with the expiry time.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &now);
		clear_dead = p->exit_state;
	} else {
		read_lock(&tasklist_lock);
		if (unlikely(p->signal == NULL)) {
			/*
			 * The process has been reaped.
			 * We can't even collect a sample any more.
			 * Call the timer disarmed, nothing else to do.
			 */
			put_task_struct(p);
			timer->it.cpu.task = NULL;
			timer->it.cpu.expires.sched = 0;
			read_unlock(&tasklist_lock);
			goto dead;
		} else {
			cpu_clock_sample_group(timer->it_clock, p, &now);
			clear_dead = (unlikely(p->exit_state) &&
				      thread_group_empty(p));
		}
		read_unlock(&tasklist_lock);
	}

	if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
		if (timer->it.cpu.incr.sched == 0 &&
		    cpu_time_before(timer->it_clock,
				    timer->it.cpu.expires, now)) {
			/*
			 * Do-nothing timer expired and has no reload,
			 * so it's as if it was never set.
			 */
			timer->it.cpu.expires.sched = 0;
			itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
			return;
		}
		/*
		 * Account for any expirations and reloads that should
		 * have happened.
		 */
		bump_cpu_timer(timer, now);
	}

	if (unlikely(clear_dead)) {
		/*
		 * We've noticed that the thread is dead, but
		 * not yet reaped.  Take this opportunity to
		 * drop our task ref.
		 */
		clear_dead_task(timer, now);
		goto dead;
	}

	if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
		sample_to_timespec(timer->it_clock,
				   cpu_time_sub(timer->it_clock,
						timer->it.cpu.expires, now),
				   &itp->it_value);
	} else {
		/*
		 * The timer should have expired already, but the firing
		 * hasn't taken place yet.  Say it's just about to expire.
		 */
		itp->it_value.tv_nsec = 1;
		itp->it_value.tv_sec = 0;
	}
}

/*
 * Check for any per-thread CPU timers that have fired and move them off
 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 */
static void check_thread_timers(struct task_struct *tsk,
				struct list_head *firing)
{
	int maxfire;
	struct list_head *timers = tsk->cpu_timers;
	struct signal_struct *const sig = tsk->signal;

	maxfire = 20;
	tsk->it_prof_expires = cputime_zero;
	while (!list_empty(timers)) {
		struct cpu_timer_list *t = list_first_entry(timers,
						      struct cpu_timer_list,
						      entry);
		if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
			tsk->it_prof_expires = t->expires.cpu;
			break;
		}
		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	++timers;
	maxfire = 20;
	tsk->it_virt_expires = cputime_zero;
	while (!list_empty(timers)) {
		struct cpu_timer_list *t = list_first_entry(timers,
						      struct cpu_timer_list,
						      entry);
		if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
			tsk->it_virt_expires = t->expires.cpu;
			break;
		}
		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	++timers;
	maxfire = 20;
	tsk->it_sched_expires = 0;
	while (!list_empty(timers)) {
		struct cpu_timer_list *t = list_first_entry(timers,
						      struct cpu_timer_list,
						      entry);
		if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
			tsk->it_sched_expires = t->expires.sched;
			break;
		}
		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	/*
	 * Check for the special case thread timers.
	 */
	if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) {
		unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
		unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur;

		if (hard != RLIM_INFINITY &&
		    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
			/*
			 * At the hard limit, we just die.
			 * No need to calculate anything else now.
			 */
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
			return;
		}
		if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) {
			/*
			 * At the soft limit, send a SIGXCPU every second.
			 */
			if (sig->rlim[RLIMIT_RTTIME].rlim_cur
			    < sig->rlim[RLIMIT_RTTIME].rlim_max) {
				sig->rlim[RLIMIT_RTTIME].rlim_cur +=
								USEC_PER_SEC;
			}
			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
		}
	}
}

/*
 * Check for any per-thread CPU timers that have fired and move them
 * off the tsk->*_timers list onto the firing list.  Per-thread timers
 * have already been taken off.
 */
static void check_process_timers(struct task_struct *tsk,
				 struct list_head *firing)
{
	int maxfire;
	struct signal_struct *const sig = tsk->signal;
	cputime_t utime, stime, ptime, virt_expires, prof_expires;
	unsigned long long sum_sched_runtime, sched_expires;
	struct task_struct *t;
	struct list_head *timers = sig->cpu_timers;

	/*
	 * Don't sample the current process CPU clocks if there are no timers.
	 */
	if (list_empty(&timers[CPUCLOCK_PROF]) &&
	    cputime_eq(sig->it_prof_expires, cputime_zero) &&
	    sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
	    list_empty(&timers[CPUCLOCK_VIRT]) &&
	    cputime_eq(sig->it_virt_expires, cputime_zero) &&
	    list_empty(&timers[CPUCLOCK_SCHED]))
		return;

	/*
	 * Collect the current process totals.
	 */
	utime = sig->utime;
	stime = sig->stime;
	sum_sched_runtime = sig->sum_sched_runtime;
	t = tsk;
	do {
		utime = cputime_add(utime, t->utime);
		stime = cputime_add(stime, t->stime);
		sum_sched_runtime += t->se.sum_exec_runtime;
		t = next_thread(t);
	} while (t != tsk);
	ptime = cputime_add(utime, stime);

	maxfire = 20;
	prof_expires = cputime_zero;
	while (!list_empty(timers)) {
		struct cpu_timer_list *t = list_first_entry(timers,
						      struct cpu_timer_list,
						      entry);
		if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
			prof_expires = t->expires.cpu;
			break;
		}
		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	++timers;
	maxfire = 20;
	virt_expires = cputime_zero;
	while (!list_empty(timers)) {
		struct cpu_timer_list *t = list_first_entry(timers,
						      struct cpu_timer_list,
						      entry);
		if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
			virt_expires = t->expires.cpu;
			break;
		}
		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	++timers;
	maxfire = 20;
	sched_expires = 0;
	while (!list_empty(timers)) {
		struct cpu_timer_list *t = list_first_entry(timers,
						      struct cpu_timer_list,
						      entry);
		if (!--maxfire || sum_sched_runtime < t->expires.sched) {
			sched_expires = t->expires.sched;
			break;
		}
		t->firing = 1;
		list_move_tail(&t->entry, firing);
	}

	/*
	 * Check for the special case process timers.
	 */
	if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
		if (cputime_ge(ptime, sig->it_prof_expires)) {
			/* ITIMER_PROF fires and reloads.  */
			sig->it_prof_expires = sig->it_prof_incr;
			if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
				sig->it_prof_expires = cputime_add(
					sig->it_prof_expires, ptime);
			}
			__group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
		}
		if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
		    (cputime_eq(prof_expires, cputime_zero) ||
		     cputime_lt(sig->it_prof_expires, prof_expires))) {
			prof_expires = sig->it_prof_expires;
		}
	}
	if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
		if (cputime_ge(utime, sig->it_virt_expires)) {
			/* ITIMER_VIRTUAL fires and reloads.  */
			sig->it_virt_expires = sig->it_virt_incr;
			if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
				sig->it_virt_expires = cputime_add(
					sig->it_virt_expires, utime);
			}
			__group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
		}
		if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
		    (cputime_eq(virt_expires, cputime_zero) ||
		     cputime_lt(sig->it_virt_expires, virt_expires))) {
			virt_expires = sig->it_virt_expires;
		}
	}
	if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
		unsigned long psecs = cputime_to_secs(ptime);
		cputime_t x;
		if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
			/*
			 * At the hard limit, we just die.
			 * No need to calculate anything else now.
			 */
			__group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
			return;
		}
		if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
			/*
			 * At the soft limit, send a SIGXCPU every second.
			 */
			__group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
			if (sig->rlim[RLIMIT_CPU].rlim_cur
			    < sig->rlim[RLIMIT_CPU].rlim_max) {
				sig->rlim[RLIMIT_CPU].rlim_cur++;
			}
		}
		x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
		if (cputime_eq(prof_expires, cputime_zero) ||
		    cputime_lt(x, prof_expires)) {
			prof_expires = x;
		}
	}

	if (!cputime_eq(prof_expires, cputime_zero) ||
	    !cputime_eq(virt_expires, cputime_zero) ||
	    sched_expires != 0) {
		/*
		 * Rebalance the threads' expiry times for the remaining
		 * process CPU timers.
		 */

		cputime_t prof_left, virt_left, ticks;
		unsigned long long sched_left, sched;
		const unsigned int nthreads = atomic_read(&sig->live);

		if (!nthreads)
			return;

		prof_left = cputime_sub(prof_expires, utime);
		prof_left = cputime_sub(prof_left, stime);
		prof_left = cputime_div_non_zero(prof_left, nthreads);
		virt_left = cputime_sub(virt_expires, utime);
		virt_left = cputime_div_non_zero(virt_left, nthreads);
		if (sched_expires) {
			sched_left = sched_expires - sum_sched_runtime;
			do_div(sched_left, nthreads);
			sched_left = max_t(unsigned long long, sched_left, 1);
		} else {
			sched_left = 0;
		}
		t = tsk;
		do {
			if (unlikely(t->flags & PF_EXITING))
				continue;

			ticks = cputime_add(cputime_add(t->utime, t->stime),
					    prof_left);
			if (!cputime_eq(prof_expires, cputime_zero) &&
			    (cputime_eq(t->it_prof_expires, cputime_zero) ||
			     cputime_gt(t->it_prof_expires, ticks))) {
				t->it_prof_expires = ticks;
			}

			ticks = cputime_add(t->utime, virt_left);
			if (!cputime_eq(virt_expires, cputime_zero) &&
			    (cputime_eq(t->it_virt_expires, cputime_zero) ||
			     cputime_gt(t->it_virt_expires, ticks))) {
				t->it_virt_expires = ticks;
			}

			sched = t->se.sum_exec_runtime + sched_left;
			if (sched_expires && (t->it_sched_expires == 0 ||
					      t->it_sched_expires > sched)) {
				t->it_sched_expires = sched;
			}
		} while ((t = next_thread(t)) != tsk);
	}
}

/*
 * This is called from the signal code (via do_schedule_next_timer)
 * when the last timer signal was delivered and we have to reload the timer.
 */
void posix_cpu_timer_schedule(struct k_itimer *timer)
{
	struct task_struct *p = timer->it.cpu.task;
	union cpu_time_count now;

	if (unlikely(p == NULL))
		/*
		 * The task was cleaned up already, no future firings.
		 */
		goto out;

	/*
	 * Fetch the current sample and update the timer's expiry time.
	 */
	if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
		cpu_clock_sample(timer->it_clock, p, &now);
		bump_cpu_timer(timer, now);
		if (unlikely(p->exit_state)) {
			clear_dead_task(timer, now);
			goto out;
		}
		read_lock(&tasklist_lock); /* arm_timer needs it.  */
	} else {
		read_lock(&tasklist_lock);
		if (unlikely(p->signal == NULL)) {
			/*
			 * The process has been reaped.
			 * We can't even collect a sample any more.
			 */
			put_task_struct(p);
			timer->it.cpu.task = p = NULL;
			timer->it.cpu.expires.sched = 0;
			goto out_unlock;
		} else if (unlikely(p->exit_state) && thread_group_empty(p)) {
			/*
			 * We've noticed that the thread is dead, but
			 * not yet reaped.  Take this opportunity to
			 * drop our task ref.
			 */
			clear_dead_task(timer, now);
			goto out_unlock;
		}
		cpu_clock_sample_group(timer->it_clock, p, &now);
		bump_cpu_timer(timer, now);
		/* Leave the tasklist_lock locked for the call below.  */
	}

	/*
	 * Now re-arm for the new expiry time.
	 */
	arm_timer(timer, now);

out_unlock:
	read_unlock(&tasklist_lock);

out:
	timer->it_overrun_last = timer->it_overrun;
	timer->it_overrun = -1;
	++timer->it_requeue_pending;
}

/*
 * This is called from the timer interrupt handler.  The irq handler has
 * already updated our counts.  We need to check if any timers fire now.
 * Interrupts are disabled.
 */
void run_posix_cpu_timers(struct task_struct *tsk)
{
	LIST_HEAD(firing);
	struct k_itimer *timer, *next;

	BUG_ON(!irqs_disabled());

#define UNEXPIRED(clock) \
		(cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
		 cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))

	if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
	    (tsk->it_sched_expires == 0 ||
	     tsk->se.sum_exec_runtime < tsk->it_sched_expires))
		return;

#undef	UNEXPIRED

	/*
	 * Double-check with locks held.
	 */
	read_lock(&tasklist_lock);
	if (likely(tsk->signal != NULL)) {
		spin_lock(&tsk->sighand->siglock);

		/*
		 * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
		 * all the timers that are firing, and put them on the firing list.
		 */
		check_thread_timers(tsk, &firing);
		check_process_timers(tsk, &firing);

		/*
		 * We must release these locks before taking any timer's lock.
		 * There is a potential race with timer deletion here, as the
		 * siglock now protects our private firing list.  We have set
		 * the firing flag in each timer, so that a deletion attempt
		 * that gets the timer lock before we do will give it up and
		 * spin until we've taken care of that timer below.
		 */
		spin_unlock(&tsk->sighand->siglock);
	}
	read_unlock(&tasklist_lock);

	/*
	 * Now that all the timers on our list have the firing flag,
	 * noone will touch their list entries but us.  We'll take
	 * each timer's lock before clearing its firing flag, so no
	 * timer call will interfere.
	 */
	list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
		int firing;
		spin_lock(&timer->it_lock);
		list_del_init(&timer->it.cpu.entry);
		firing = timer->it.cpu.firing;
		timer->it.cpu.firing = 0;
		/*
		 * The firing flag is -1 if we collided with a reset
		 * of the timer, which already reported this
		 * almost-firing as an overrun.  So don't generate an event.
		 */
		if (likely(firing >= 0)) {
			cpu_timer_fire(timer);
		}
		spin_unlock(&timer->it_lock);
	}
}

/*
 * Set one of the process-wide special case CPU timers.
 * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
 * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
 * absolute; non-null for ITIMER_*, where *newval is relative and we update
 * it to be absolute, *oldval is absolute and we update it to be relative.
 */
void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
			   cputime_t *newval, cputime_t *oldval)
{
	union cpu_time_count now;
	struct list_head *head;

	BUG_ON(clock_idx == CPUCLOCK_SCHED);
	cpu_clock_sample_group_locked(clock_idx, tsk, &now);

	if (oldval) {
		if (!cputime_eq(*oldval, cputime_zero)) {
			if (cputime_le(*oldval, now.cpu)) {
				/* Just about to fire. */
				*oldval = jiffies_to_cputime(1);
			} else {
				*oldval = cputime_sub(*oldval, now.cpu);
			}
		}

		if (cputime_eq(*newval, cputime_zero))
			return;
		*newval = cputime_add(*newval, now.cpu);

		/*
		 * If the RLIMIT_CPU timer will expire before the
		 * ITIMER_PROF timer, we have nothing else to do.
		 */
		if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
		    < cputime_to_secs(*newval))
			return;
	}

	/*
	 * Check whether there are any process timers already set to fire
	 * before this one.  If so, we don't have anything more to do.
	 */
	head = &tsk->signal->cpu_timers[clock_idx];
	if (list_empty(head) ||
	    cputime_ge(list_first_entry(head,
				  struct cpu_timer_list, entry)->expires.cpu,
		       *newval)) {
		/*
		 * Rejigger each thread's expiry time so that one will
		 * notice before we hit the process-cumulative expiry time.
		 */
		union cpu_time_count expires = { .sched = 0 };
		expires.cpu = *newval;
		process_timer_rebalance(tsk, clock_idx, expires, now);
	}
}

static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
			    struct timespec *rqtp, struct itimerspec *it)
{
	struct k_itimer timer;
	int error;

	/*
	 * Set up a temporary timer and then wait for it to go off.
	 */
	memset(&timer, 0, sizeof timer);
	spin_lock_init(&timer.it_lock);
	timer.it_clock = which_clock;
	timer.it_overrun = -1;
	error = posix_cpu_timer_create(&timer);
	timer.it_process = current;
	if (!error) {
		static struct itimerspec zero_it;

		memset(it, 0, sizeof *it);
		it->it_value = *rqtp;

		spin_lock_irq(&timer.it_lock);
		error = posix_cpu_timer_set(&timer, flags, it, NULL);
		if (error) {
			spin_unlock_irq(&timer.it_lock);
			return error;
		}

		while (!signal_pending(current)) {
			if (timer.it.cpu.expires.sched == 0) {
				/*
				 * Our timer fired and was reset.
				 */
				spin_unlock_irq(&timer.it_lock);
				return 0;
			}

			/*
			 * Block until cpu_timer_fire (or a signal) wakes us.
			 */
			__set_current_state(TASK_INTERRUPTIBLE);
			spin_unlock_irq(&timer.it_lock);
			schedule();
			spin_lock_irq(&timer.it_lock);
		}

		/*
		 * We were interrupted by a signal.
		 */
		sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
		posix_cpu_timer_set(&timer, 0, &zero_it, it);
		spin_unlock_irq(&timer.it_lock);

		if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
			/*
			 * It actually did fire already.
			 */
			return 0;
		}

		error = -ERESTART_RESTARTBLOCK;
	}

	return error;
}

int posix_cpu_nsleep(const clockid_t which_clock, int flags,
		     struct timespec *rqtp, struct timespec __user *rmtp)
{
	struct restart_block *restart_block =
	    &current_thread_info()->restart_block;
	struct itimerspec it;
	int error;

	/*
	 * Diagnose required errors first.
	 */
	if (CPUCLOCK_PERTHREAD(which_clock) &&
	    (CPUCLOCK_PID(which_clock) == 0 ||
	     CPUCLOCK_PID(which_clock) == current->pid))
		return -EINVAL;

	error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);

	if (error == -ERESTART_RESTARTBLOCK) {

	       	if (flags & TIMER_ABSTIME)
			return -ERESTARTNOHAND;
		/*
	 	 * Report back to the user the time still remaining.
	 	 */
		if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
			return -EFAULT;

		restart_block->fn = posix_cpu_nsleep_restart;
		restart_block->arg0 = which_clock;
		restart_block->arg1 = (unsigned long) rmtp;
		restart_block->arg2 = rqtp->tv_sec;
		restart_block->arg3 = rqtp->tv_nsec;
	}
	return error;
}

long posix_cpu_nsleep_restart(struct restart_block *restart_block)
{
	clockid_t which_clock = restart_block->arg0;
	struct timespec __user *rmtp;
	struct timespec t;
	struct itimerspec it;
	int error;

	rmtp = (struct timespec __user *) restart_block->arg1;
	t.tv_sec = restart_block->arg2;
	t.tv_nsec = restart_block->arg3;

	restart_block->fn = do_no_restart_syscall;
	error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);

	if (error == -ERESTART_RESTARTBLOCK) {
		/*
	 	 * Report back to the user the time still remaining.
	 	 */
		if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
			return -EFAULT;

		restart_block->fn = posix_cpu_nsleep_restart;
		restart_block->arg0 = which_clock;
		restart_block->arg1 = (unsigned long) rmtp;
		restart_block->arg2 = t.tv_sec;
		restart_block->arg3 = t.tv_nsec;
	}
	return error;

}


#define PROCESS_CLOCK	MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
#define THREAD_CLOCK	MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)

static int process_cpu_clock_getres(const clockid_t which_clock,
				    struct timespec *tp)
{
	return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
}
static int process_cpu_clock_get(const clockid_t which_clock,
				 struct timespec *tp)
{
	return posix_cpu_clock_get(PROCESS_CLOCK, tp);
}
static int process_cpu_timer_create(struct k_itimer *timer)
{
	timer->it_clock = PROCESS_CLOCK;
	return posix_cpu_timer_create(timer);
}
static int process_cpu_nsleep(const clockid_t which_clock, int flags,
			      struct timespec *rqtp,
			      struct timespec __user *rmtp)
{
	return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
}
static long process_cpu_nsleep_restart(struct restart_block *restart_block)
{
	return -EINVAL;
}
static int thread_cpu_clock_getres(const clockid_t which_clock,
				   struct timespec *tp)
{
	return posix_cpu_clock_getres(THREAD_CLOCK, tp);
}
static int thread_cpu_clock_get(const clockid_t which_clock,
				struct timespec *tp)
{
	return posix_cpu_clock_get(THREAD_CLOCK, tp);
}
static int thread_cpu_timer_create(struct k_itimer *timer)
{
	timer->it_clock = THREAD_CLOCK;
	return posix_cpu_timer_create(timer);
}
static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
			      struct timespec *rqtp, struct timespec __user *rmtp)
{
	return -EINVAL;
}
static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
{
	return -EINVAL;
}

static __init int init_posix_cpu_timers(void)
{
	struct k_clock process = {
		.clock_getres = process_cpu_clock_getres,
		.clock_get = process_cpu_clock_get,
		.clock_set = do_posix_clock_nosettime,
		.timer_create = process_cpu_timer_create,
		.nsleep = process_cpu_nsleep,
		.nsleep_restart = process_cpu_nsleep_restart,
	};
	struct k_clock thread = {
		.clock_getres = thread_cpu_clock_getres,
		.clock_get = thread_cpu_clock_get,
		.clock_set = do_posix_clock_nosettime,
		.timer_create = thread_cpu_timer_create,
		.nsleep = thread_cpu_nsleep,
		.nsleep_restart = thread_cpu_nsleep_restart,
	};

	register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
	register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);

	return 0;
}
__initcall(init_posix_cpu_timers);
generated by cgit v1.2.2 (git 2.25.0) at 2025-02-06 12:11:12 -0500