aboutsummaryrefslogblamecommitdiffstats
path: root/erts/emulator/sys/common/erl_poll.c
blob: 3ae5b8d747ca3a294f40bebcc516a92cf7015a9f (plain) (tree)
1
2
3
4
5
6
7
8
9
10
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
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
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897

                   
  
                                                        
  




                                                                      
  



                                                                         
  













































































































                                                                               
                                                              
                                       
                                                     
                                    
                                           








                                         



                                                   
                                                                       
                                                     
                                                                       
                                               
                                                             





                                                   






































































                                                                              
                                     






























                                                       
                                             

               
                           

                                       






                             



                                       
      
                                






                                            
                                                  






















































                                                           








                                                              
                            















































                                                                             






                                                                              
                                            
 



















                                                                                




                                                                       
               






















































































































































































































































































































































































































                                                                              
                                                             
















































                                                                                
                                                 


                                               
                                                 
























































































                                                                            
                                                         



                       
                                                         








































































                                                                              
                                                 






                                                                        
                                                 


                                               
                                                 
















































                                                                           
                                                     






















































































                                                                           
                                                 

























                                                                         
                                                     

















































                                                                               
                                                     






                                                                 
                                                     










































































                                                                                 
                                                                                 






































































































                                                                                    










                                                     



                                                

                            

                      
                           

                     









                                                                                  



                          


                                                    


                   
                           


                     



















































































































































































































































































































































































                                                                                

                                                      



                                                       


                                                          
                             
                                                                          





























                                                                                
                                                                       

























































































                                                                               





                                                              

                              















                                                       
                






























                                                              
                                                                              









                                  
                                                                














                                                                              
                                                          




                                                                       



                               
      







                                                                      


                                                           
 
                                                          




                                                                             








                                                             
      

























































                                                                                
                                                 


















































                                                            
                                                         

               
                                       
                                           


                                                             
                                       
                         




















                                                                          
                                                            










                                                        
                                                                                              





































































































                                                                               
                                









































                              
                                                                         










































































































                                                                                  



                                                                      






































































































































                                                                              
/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 2006-2011. All Rights Reserved.
 *
 * The contents of this file are subject to the Erlang Public License,
 * Version 1.1, (the "License"); you may not use this file except in
 * compliance with the License. You should have received a copy of the
 * Erlang Public License along with this software. If not, it can be
 * retrieved online at http://www.erlang.org/.
 *
 * Software distributed under the License is distributed on an "AS IS"
 * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
 * the License for the specific language governing rights and limitations
 * under the License.
 *
 * %CopyrightEnd%
 */

/*
 * Description:	Poll interface suitable for ERTS with or without
 *              SMP support.
 *
 *		The interface is currently implemented using:
 *		- select
 *		- poll
 *              - /dev/poll
 *              - epoll with poll or select as fallback
 *              - kqueue with poll or select as fallback
 *
 *		Some time in the future it will also be
 *		implemented using Solaris ports.
 *
 *
 *
 * Author: 	Rickard Green
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#ifndef WANT_NONBLOCKING
#  define WANT_NONBLOCKING
#endif
#define ERTS_WANT_GOT_SIGUSR1

#include "erl_poll.h"
#if ERTS_POLL_USE_KQUEUE
#  include <sys/types.h>
#  include <sys/event.h>
#  include <sys/time.h>
#endif
#if ERTS_POLL_USE_SELECT
#  ifdef SYS_SELECT_H
#    include <sys/select.h>
#  endif
#  ifdef VXWORKS
#    include <selectLib.h>
#  endif
#endif
#ifndef VXWORKS
#  ifdef NO_SYSCONF
#    if ERTS_POLL_USE_SELECT
#      include <sys/param.h>
#    else
#      include <limits.h>
#    endif
#  endif
#endif
#include "erl_driver.h"
#include "erl_alloc.h"

#if !defined(ERTS_POLL_USE_EPOLL) \
    && !defined(ERTS_POLL_USE_DEVPOLL)  \
    && !defined(ERTS_POLL_USE_POLL) \
    && !defined(ERTS_POLL_USE_SELECT)
#error "Missing implementation of erts_poll()"
#endif

#if defined(ERTS_KERNEL_POLL_VERSION) && !ERTS_POLL_USE_KERNEL_POLL
#error "Missing kernel poll implementation of erts_poll()"
#endif

#if defined(ERTS_NO_KERNEL_POLL_VERSION) && ERTS_POLL_USE_KERNEL_POLL
#error "Kernel poll used when it shouldn't be used"
#endif

#if 0
#define ERTS_POLL_DEBUG_PRINT
#endif

#if defined(DEBUG) && 0
#define HARD_DEBUG
#endif

#define ERTS_POLL_USE_BATCH_UPDATE_POLLSET (ERTS_POLL_USE_DEVPOLL \
					    || ERTS_POLL_USE_KQUEUE)
#define ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE \
   (defined(ERTS_SMP) || ERTS_POLL_USE_KERNEL_POLL || ERTS_POLL_USE_POLL)

#define ERTS_POLL_USE_CONCURRENT_UPDATE \
   (defined(ERTS_SMP) && ERTS_POLL_USE_EPOLL)

#define ERTS_POLL_COALESCE_KP_RES (ERTS_POLL_USE_KQUEUE || ERTS_POLL_USE_EPOLL)

#define FDS_STATUS_EXTRA_FREE_SIZE 128
#define POLL_FDS_EXTRA_FREE_SIZE 128

#ifdef ERTS_POLL_NEED_ASYNC_INTERRUPT_SUPPORT
#  define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 1
#else
#  define ERTS_POLL_ASYNC_INTERRUPT_SUPPORT 0
#endif

#define ERTS_POLL_USE_WAKEUP_PIPE \
   (ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP))

#ifdef ERTS_SMP

#define ERTS_POLLSET_LOCK(PS) \
  erts_smp_mtx_lock(&(PS)->mtx)
#define ERTS_POLLSET_UNLOCK(PS) \
  erts_smp_mtx_unlock(&(PS)->mtx)

#define ERTS_POLLSET_SET_POLLED_CHK(PS) \
  ((int) erts_atomic32_xchg(&(PS)->polled, (erts_aint32_t) 1))
#define ERTS_POLLSET_UNSET_POLLED(PS) \
  erts_atomic32_set(&(PS)->polled, (erts_aint32_t) 0)
#define ERTS_POLLSET_IS_POLLED(PS) \
  ((int) erts_atomic32_read(&(PS)->polled))

#else

#define ERTS_POLLSET_LOCK(PS)
#define ERTS_POLLSET_UNLOCK(PS)
#define ERTS_POLLSET_SET_POLLED_CHK(PS) 0
#define ERTS_POLLSET_UNSET_POLLED(PS)
#define ERTS_POLLSET_IS_POLLED(PS) 0

#endif

#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
#define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS) \
  erts_smp_atomic32_set(&(PS)->have_update_requests, (erts_aint32_t) 1)
#define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS) \
  erts_smp_atomic32_set(&(PS)->have_update_requests, (erts_aint32_t) 0)
#define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) \
  ((int) erts_smp_atomic32_read(&(PS)->have_update_requests))
#else
#define ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(PS)
#define ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(PS)
#define ERTS_POLLSET_HAVE_UPDATE_REQUESTS(PS) 0
#endif

#if ERTS_POLL_USE_FALLBACK
#  if ERTS_POLL_USE_POLL
#    define ERTS_POLL_NEED_FALLBACK(PS) ((PS)->no_poll_fds > 1)
#  elif ERTS_POLL_USE_SELECT
#    define ERTS_POLL_NEED_FALLBACK(PS) ((PS)->no_select_fds > 1)
#  endif
#endif
/*
 * --- Data types ------------------------------------------------------------
 */

#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
#define ERTS_POLLSET_UPDATE_REQ_BLOCK_SIZE 128

typedef struct ErtsPollSetUpdateRequestsBlock_ ErtsPollSetUpdateRequestsBlock;
struct ErtsPollSetUpdateRequestsBlock_ {
    ErtsPollSetUpdateRequestsBlock *next;
    int len;
    int fds[ERTS_POLLSET_UPDATE_REQ_BLOCK_SIZE];
};

#endif


#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
#  define ERTS_POLL_FD_FLG_INURQ	(((unsigned short) 1) << 0)
#endif
#if ERTS_POLL_USE_FALLBACK
#  define ERTS_POLL_FD_FLG_INFLBCK	(((unsigned short) 1) << 1)
#  define ERTS_POLL_FD_FLG_USEFLBCK	(((unsigned short) 1) << 2)
#endif
#if ERTS_POLL_USE_KERNEL_POLL || defined(ERTS_SMP)
#  define ERTS_POLL_FD_FLG_RST		(((unsigned short) 1) << 3)
#endif
typedef struct {
#if ERTS_POLL_USE_POLL
    int pix;
#endif
    ErtsPollEvents used_events;
    ErtsPollEvents events;
#if ERTS_POLL_COALESCE_KP_RES
    unsigned short res_ev_ix;
#endif
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE || ERTS_POLL_USE_FALLBACK
    unsigned short flags;
#endif

} ErtsFdStatus;


#if ERTS_POLL_COALESCE_KP_RES
/* res_ev_ix max value */
#define ERTS_POLL_MAX_RES ((1 << sizeof(unsigned short)*8) - 1)
#endif

#if ERTS_POLL_USE_KQUEUE

#define ERTS_POLL_KQ_OP_HANDLED			1
#define ERTS_POLL_KQ_OP_DEL_R			2
#define ERTS_POLL_KQ_OP_DEL_W			3
#define ERTS_POLL_KQ_OP_ADD_R			4
#define ERTS_POLL_KQ_OP_ADD_W			5
#define ERTS_POLL_KQ_OP_ADD2_R			6
#define ERTS_POLL_KQ_OP_ADD2_W			7

#endif

struct ErtsPollSet_ {
    ErtsPollSet next;
    int internal_fd_limit;
    ErtsFdStatus *fds_status;
    erts_smp_atomic_t no_of_user_fds;
    int fds_status_len;
#if ERTS_POLL_USE_KERNEL_POLL
    int kp_fd;
    int res_events_len;
#if ERTS_POLL_USE_EPOLL
    struct epoll_event *res_events;
#elif ERTS_POLL_USE_KQUEUE
    struct kevent *res_events;
#elif ERTS_POLL_USE_DEVPOLL
    struct pollfd *res_events;
#endif
#endif /* ERTS_POLL_USE_KERNEL_POLL */
#if ERTS_POLL_USE_POLL
    int next_poll_fds_ix;
    int no_poll_fds;
    int poll_fds_len;
    struct pollfd*poll_fds;
#elif ERTS_POLL_USE_SELECT
    int next_sel_fd;
    int max_fd;
#if ERTS_POLL_USE_FALLBACK
    int no_select_fds;
#endif
    fd_set input_fds;
    fd_set res_input_fds;
    fd_set output_fds;
    fd_set res_output_fds;
#endif
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    ErtsPollSetUpdateRequestsBlock update_requests;
    ErtsPollSetUpdateRequestsBlock *curr_upd_req_block;
    erts_smp_atomic32_t have_update_requests;
#endif
#ifdef ERTS_SMP
    erts_atomic32_t polled;
    erts_smp_mtx_t mtx;
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
#endif
#if ERTS_POLL_USE_WAKEUP_PIPE
    int wake_fds[2];
#endif
#if ERTS_POLL_USE_FALLBACK
    int fallback_used;
#endif
#ifdef ERTS_SMP
    erts_atomic32_t wakeup_state;
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    volatile int wakeup_state;
#endif
    erts_smp_atomic32_t timeout;
#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
    erts_smp_atomic_t no_avoided_wakeups;
    erts_smp_atomic_t no_avoided_interrupts;
    erts_smp_atomic_t no_interrupt_timed;
#endif
};

void erts_silence_warn_unused_result(long unused);
static void fatal_error(char *format, ...);
static void fatal_error_async_signal_safe(char *error_str);

static int max_fds = -1;
static ErtsPollSet pollsets;
static erts_smp_spinlock_t pollsets_lock;

#if ERTS_POLL_USE_POLL

static ERTS_INLINE short
ev2pollev(ErtsPollEvents ev)
{
#if !ERTS_POLL_USE_FALLBACK || ERTS_POLL_USE_KQUEUE
    return ERTS_POLL_EV_E2N(ev);
#else /* Note, we only map events we are interested in */
    short res_ev = (short) 0;
    if (ev & ERTS_POLL_EV_IN)
	res_ev |= ERTS_POLL_EV_NKP_IN;
    if (ev & ERTS_POLL_EV_OUT)
	res_ev |= ERTS_POLL_EV_NKP_OUT;
    return res_ev;
#endif
}

static ERTS_INLINE ErtsPollEvents
pollev2ev(short ev)
{
#if !ERTS_POLL_USE_FALLBACK || ERTS_POLL_USE_KQUEUE
    return ERTS_POLL_EV_N2E(ev);
#else /* Note, we only map events we are interested in */
    ErtsPollEvents res_ev = (ErtsPollEvents) 0;
    if (ev & ERTS_POLL_EV_NKP_IN)
	res_ev |= ERTS_POLL_EV_IN;
    if (ev & ERTS_POLL_EV_NKP_OUT)
	res_ev |= ERTS_POLL_EV_OUT;
    if (ev & ERTS_POLL_EV_NKP_ERR)
	res_ev |= ERTS_POLL_EV_ERR;
    if (ev & ERTS_POLL_EV_NKP_NVAL)
	res_ev |= ERTS_POLL_EV_NVAL;
    return res_ev;
#endif
}

#endif

#ifdef HARD_DEBUG
static void check_poll_result(ErtsPollResFd pr[], int len);
#if ERTS_POLL_USE_DEVPOLL
static void check_poll_status(ErtsPollSet ps);
#endif /* ERTS_POLL_USE_DEVPOLL */
#endif /* HARD_DEBUG */
#ifdef ERTS_POLL_DEBUG_PRINT
static void print_misc_debug_info(void);
#endif

#define ERTS_POLL_NOT_WOKEN	0
#define ERTS_POLL_WOKEN		-1
#define ERTS_POLL_WOKEN_INTR	1

static ERTS_INLINE void
reset_wakeup_state(ErtsPollSet ps)
{
#ifdef ERTS_SMP
    erts_atomic32_set(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN);
    ERTS_THR_MEMORY_BARRIER;
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    ps->wakeup_state = 0;
#endif
}

static ERTS_INLINE int
is_woken(ErtsPollSet ps)
{
#ifdef ERTS_SMP
    return erts_atomic32_read_acqb(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN;
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    return ps->wakeup_state != ERTS_POLL_NOT_WOKEN;
#else
    return 0;
#endif
}

static ERTS_INLINE int
is_interrupted_reset(ErtsPollSet ps)
{
#ifdef ERTS_SMP
    return (erts_atomic32_xchg(&ps->wakeup_state, ERTS_POLL_NOT_WOKEN)
	    == ERTS_POLL_WOKEN_INTR);
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    int res = ps->wakeup_state == ERTS_POLL_WOKEN_INTR;
    ps->wakeup_state = ERTS_POLL_NOT_WOKEN;
    return res;
#else
    return 0;
#endif
}

static ERTS_INLINE void
woke_up(ErtsPollSet ps)
{
#ifdef ERTS_SMP
    erts_aint32_t wakeup_state = erts_atomic32_read(&ps->wakeup_state);
    if (wakeup_state == ERTS_POLL_NOT_WOKEN)
	(void) erts_atomic32_cmpxchg(&ps->wakeup_state,
				     ERTS_POLL_WOKEN,
				     ERTS_POLL_NOT_WOKEN);
    ASSERT(erts_atomic32_read(&ps->wakeup_state) != ERTS_POLL_NOT_WOKEN);
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    if (ps->wakeup_state == ERTS_POLL_NOT_WOKEN)
	ps->wakeup_state = ERTS_POLL_WOKEN;
#endif
}

/*
 * --- Wakeup pipe -----------------------------------------------------------
 */

#if ERTS_POLL_USE_WAKEUP_PIPE

static ERTS_INLINE void
wake_poller(ErtsPollSet ps, int interrupted)
{
    int wake;
#ifdef ERTS_SMP
    erts_aint32_t wakeup_state;
    if (!interrupted)
	wakeup_state = erts_atomic32_cmpxchg_relb(&ps->wakeup_state,
						  ERTS_POLL_WOKEN,
						  ERTS_POLL_NOT_WOKEN);
    else {
	/*
	 * We might unnecessarily write to the pipe, however,
	 * that isn't problematic.
	 */
	wakeup_state = erts_atomic32_read(&ps->wakeup_state);
	erts_atomic32_set_relb(&ps->wakeup_state, ERTS_POLL_WOKEN_INTR);
    }
    wake = wakeup_state == ERTS_POLL_NOT_WOKEN;
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    wake = ps->wakeup_state == ERTS_POLL_NOT_WOKEN;
    ps->wakeup_state = interrupted ? ERTS_POLL_WOKEN_INTR : ERTS_POLL_NOT_WOKEN;
#endif
    /*
     * NOTE: This function might be called from signal handlers in the
     *       non-smp case; therefore, it has to be async-signal safe in
     *       the non-smp case.
     */
    if (wake) {
	ssize_t res;
	if (ps->wake_fds[1] < 0)
	    return; /* Not initialized yet */
	do {
	    /* write() is async-signal safe (according to posix) */
	    res = write(ps->wake_fds[1], "!", 1);
	} while (res < 0 && errno == EINTR);
	if (res <= 0 && errno != ERRNO_BLOCK) {
	    fatal_error_async_signal_safe(__FILE__
					  ":XXX:wake_poller(): "
					  "Failed to write on wakeup pipe\n");
	}
    }
}

static ERTS_INLINE void
cleanup_wakeup_pipe(ErtsPollSet ps)
{
    int fd = ps->wake_fds[0];
    int res;
    do {
	char buf[32];
	res = read(fd, buf, sizeof(buf));
    } while (res > 0 || (res < 0 && errno == EINTR));
    if (res < 0 && errno != ERRNO_BLOCK) {
	fatal_error("%s:%d:cleanup_wakeup_pipe(): "
		    "Failed to read on wakeup pipe fd=%d: "
		    "%s (%d)\n",
		    __FILE__, __LINE__,
		    fd,
		    erl_errno_id(errno), errno);
    }
}

static void
create_wakeup_pipe(ErtsPollSet ps)
{
    int do_wake = 0;
    int wake_fds[2];
    ps->wake_fds[0] = -1;
    ps->wake_fds[1] = -1;
    if (pipe(wake_fds) < 0) {
	fatal_error("%s:%d:create_wakeup_pipe(): "
		    "Failed to create pipe: %s (%d)\n",
		    __FILE__,
		    __LINE__,
		    erl_errno_id(errno),
		    errno);
    }
    SET_NONBLOCKING(wake_fds[0]);
    SET_NONBLOCKING(wake_fds[1]);

#ifdef ERTS_POLL_DEBUG_PRINT
    erts_printf("wakeup fds = {%d, %d}\n", wake_fds[0], wake_fds[1]);
#endif

    ERTS_POLL_EXPORT(erts_poll_control)(ps,
					wake_fds[0],
					ERTS_POLL_EV_IN,
					1, &do_wake);
#if ERTS_POLL_USE_FALLBACK
    /* We depend on the wakeup pipe being handled by kernel poll */
    if (ps->fds_status[wake_fds[0]].flags & ERTS_POLL_FD_FLG_INFLBCK)
	fatal_error("%s:%d:create_wakeup_pipe(): Internal error\n",
		    __FILE__, __LINE__);
#endif
    if (ps->internal_fd_limit <= wake_fds[1])
	ps->internal_fd_limit = wake_fds[1] + 1;
    if (ps->internal_fd_limit <= wake_fds[0])
	ps->internal_fd_limit = wake_fds[0] + 1;
    ps->wake_fds[0] = wake_fds[0];
    ps->wake_fds[1] = wake_fds[1];
}

#endif /* ERTS_POLL_USE_WAKEUP_PIPE */

/*
 * --- Poll set update requests ----------------------------------------------
 */
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE

static ERTS_INLINE void
enqueue_update_request(ErtsPollSet ps, int fd)
{
    ErtsPollSetUpdateRequestsBlock *urqbp;

    ASSERT(fd < ps->fds_status_len);

    if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INURQ)
	return;

    if (ps->update_requests.len == 0)
	ERTS_POLLSET_SET_HAVE_UPDATE_REQUESTS(ps);

    urqbp = ps->curr_upd_req_block;

    if (urqbp->len == ERTS_POLLSET_UPDATE_REQ_BLOCK_SIZE) {
	ASSERT(!urqbp->next);
	urqbp = erts_alloc(ERTS_ALC_T_POLLSET_UPDREQ,
			   sizeof(ErtsPollSetUpdateRequestsBlock));
	ps->curr_upd_req_block->next = urqbp;
	ps->curr_upd_req_block = urqbp;
	urqbp->next = NULL;
	urqbp->len = 0;
    }

    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INURQ;
    urqbp->fds[urqbp->len++] = fd;
}

static ERTS_INLINE void
free_update_requests_block(ErtsPollSet ps,
			   ErtsPollSetUpdateRequestsBlock *urqbp)
{
    if (urqbp != &ps->update_requests)
	erts_free(ERTS_ALC_T_POLLSET_UPDREQ, (void *) urqbp);
    else {
	urqbp->next = NULL;
	urqbp->len = 0;
    }
}

#endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */

/*
 * --- Growing poll set structures -------------------------------------------
 */

#if ERTS_POLL_USE_KERNEL_POLL
static void
grow_res_events(ErtsPollSet ps, int new_len)
{
    size_t new_size = sizeof(
#if ERTS_POLL_USE_EPOLL
	struct epoll_event
#elif ERTS_POLL_USE_DEVPOLL
	struct pollfd
#elif ERTS_POLL_USE_KQUEUE
	struct kevent
#endif
	)*new_len;
    /* We do not need to save previously stored data */
    if (ps->res_events)
	erts_free(ERTS_ALC_T_POLL_RES_EVS, ps->res_events);
    ps->res_events = erts_alloc(ERTS_ALC_T_POLL_RES_EVS, new_size);
    ps->res_events_len = new_len;
}
#endif /* ERTS_POLL_USE_KERNEL_POLL */

#if ERTS_POLL_USE_POLL
static void
grow_poll_fds(ErtsPollSet ps, int min_ix)
{
    int i;
    int new_len = min_ix + 1 + POLL_FDS_EXTRA_FREE_SIZE;
    if (new_len > max_fds)
	new_len = max_fds;
    ps->poll_fds = (ps->poll_fds_len
		    ? erts_realloc(ERTS_ALC_T_POLL_FDS,
				   ps->poll_fds,
				   sizeof(struct pollfd)*new_len)
		    : erts_alloc(ERTS_ALC_T_POLL_FDS,
				 sizeof(struct pollfd)*new_len));
    for (i = ps->poll_fds_len; i < new_len; i++) {
	ps->poll_fds[i].fd = -1;
	ps->poll_fds[i].events = (short) 0;
	ps->poll_fds[i].revents = (short) 0;
    }
    ps->poll_fds_len = new_len;
}
#endif

static void
grow_fds_status(ErtsPollSet ps, int min_fd)
{
    int i;
    int new_len = min_fd + 1 + FDS_STATUS_EXTRA_FREE_SIZE;
    ASSERT(min_fd < max_fds);
    if (new_len > max_fds)
	new_len = max_fds;
    ps->fds_status = (ps->fds_status_len
		      ? erts_realloc(ERTS_ALC_T_FD_STATUS,
				     ps->fds_status,
				     sizeof(ErtsFdStatus)*new_len)
		      : erts_alloc(ERTS_ALC_T_FD_STATUS,
				   sizeof(ErtsFdStatus)*new_len));
    for (i = ps->fds_status_len; i < new_len; i++) {
#if ERTS_POLL_USE_POLL
	ps->fds_status[i].pix = -1;
#endif
	ps->fds_status[i].used_events = (ErtsPollEvents) 0;
	ps->fds_status[i].events = (ErtsPollEvents) 0;
#if ERTS_POLL_COALESCE_KP_RES
	ps->fds_status[i].res_ev_ix = (unsigned short) ERTS_POLL_MAX_RES;
#endif
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE || ERTS_POLL_USE_FALLBACK
	ps->fds_status[i].flags = (unsigned short) 0;
#endif
    }
    ps->fds_status_len = new_len;
}

/*
 * --- Selecting fd to poll on -----------------------------------------------
 */

#if ERTS_POLL_USE_FALLBACK
static int update_fallback_pollset(ErtsPollSet ps, int fd);
#endif

static ERTS_INLINE int
need_update(ErtsPollSet ps, int fd)
{
#if ERTS_POLL_USE_KERNEL_POLL
    int reset;
#endif

    ASSERT(fd < ps->fds_status_len);

#if ERTS_POLL_USE_KERNEL_POLL
    reset = (int) (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST);
    if (reset && !ps->fds_status[fd].used_events) {
	ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
	reset = 0;
    }
#elif defined(ERTS_SMP)
    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
#endif

    if (ps->fds_status[fd].used_events != ps->fds_status[fd].events)
	return 1;

#if ERTS_POLL_USE_KERNEL_POLL
    return reset;
#else
    return 0;
#endif
}

#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET

#if ERTS_POLL_USE_KQUEUE
#define ERTS_POLL_MIN_BATCH_BUF_SIZE 128
#else
#define ERTS_POLL_MIN_BATCH_BUF_SIZE 64
#endif

typedef struct {
    int len;
    int size;
#if ERTS_POLL_USE_DEVPOLL
    struct pollfd *buf;
#elif ERTS_POLL_USE_KQUEUE
    struct kevent *buf;
    struct kevent *ebuf;
#endif
} ErtsPollBatchBuf;


static ERTS_INLINE void
setup_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
{
    bbp->len = 0;
#if ERTS_POLL_USE_DEVPOLL
    bbp->size = ps->res_events_len;
    bbp->buf = ps->res_events;
#elif ERTS_POLL_USE_KQUEUE
    bbp->size = ps->res_events_len/2;
    bbp->buf = ps->res_events;
    bbp->ebuf = bbp->buf + bbp->size;
#endif
}


#if ERTS_POLL_USE_DEVPOLL

static void
write_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
{
    ssize_t wres;
    char *buf = (char *) bbp->buf;
    size_t buf_size = sizeof(struct pollfd)*bbp->len;
    
    while (1) {
	wres = write(ps->kp_fd, (void *) buf, buf_size);
	if (wres < 0) {
	    if (errno == EINTR)
		continue;
	    fatal_error("%s:%d:write_batch_buf(): "
			"Failed to write to /dev/poll: "
			"%s (%d)\n",
			__FILE__, __LINE__,
			erl_errno_id(errno), errno);
	}
	buf_size -= wres;
	if (buf_size <= 0)
	    break;
	buf += wres;
    }

    if (buf_size < 0) {
	fatal_error("%s:%d:write_devpoll_buf(): Internal error\n",
		    __FILE__, __LINE__);
    }
    bbp->len = 0;
}

#elif ERTS_POLL_USE_KQUEUE

static void
write_batch_buf(ErtsPollSet ps, ErtsPollBatchBuf *bbp)
{
    int res;
    int len = bbp->len;
    struct kevent *buf = bbp->buf;
    struct timespec ts = {0, 0};

    do {
	res = kevent(ps->kp_fd, buf, len, NULL, 0, &ts);
    } while (res < 0 && errno == EINTR);
    if (res < 0) {
	int i;
	struct kevent *ebuf = bbp->ebuf;
	do {
	    res = kevent(ps->kp_fd, buf, len, ebuf, len, &ts);
	} while (res < 0 && errno == EINTR);
	if (res < 0) {
	    fatal_error("%s:%d: kevent() failed: %s (%d)\n",
			__FILE__, __LINE__, erl_errno_id(errno), errno);
	}
	for (i = 0; i < res; i++) {
	    if (ebuf[i].flags & EV_ERROR) {
		short filter;
		int fd = (int) ebuf[i].ident;

		switch ((int) ebuf[i].udata) {

		    /*
		     * Since we use a lazy update approach EV_DELETE will
		     * frequently fail. This since kqueue automatically
		     * removes a file descriptor that is closed from the
		     * poll set.
		     */
		case ERTS_POLL_KQ_OP_DEL_R:
		case ERTS_POLL_KQ_OP_DEL_W:
		case ERTS_POLL_KQ_OP_HANDLED:
		    break;

		    /*
		     * According to the kqueue man page EVFILT_READ support
		     * does not imply EVFILT_WRITE support; therefore,
		     * if an EV_ADD fail, we may have to remove other
		     * events on this fd in the kqueue pollset before
		     * adding fd to the fallback pollset.
		     */
		case ERTS_POLL_KQ_OP_ADD_W:
		    if (ps->fds_status[fd].used_events & ERTS_POLL_EV_IN) {
			filter = EVFILT_READ;
			goto rm_add_fb;
		    }
		    goto add_fb;
		case ERTS_POLL_KQ_OP_ADD_R:
		    if (ps->fds_status[fd].used_events & ERTS_POLL_EV_OUT) {
			filter = EVFILT_WRITE;
			goto rm_add_fb;
		    }
		    goto add_fb;
		case ERTS_POLL_KQ_OP_ADD2_W:
		case ERTS_POLL_KQ_OP_ADD2_R: {
		    int j;
		    for (j = i+1; j < res; j++) {
			if (fd == (int) ebuf[j].ident) {
			    ebuf[j].udata = (void *) ERTS_POLL_KQ_OP_HANDLED;
			    if (!(ebuf[j].flags & EV_ERROR)) {
				switch ((int) ebuf[j].udata) {
				case ERTS_POLL_KQ_OP_ADD2_W:
				    filter = EVFILT_WRITE;
				    goto rm_add_fb;
				case ERTS_POLL_KQ_OP_ADD2_R:
				    filter = EVFILT_READ;
				    goto rm_add_fb;
				default:
				    fatal_error("%s:%d:write_batch_buf(): "
						"Internal error",
						__FILE__, __LINE__);
				    break;
				}
			    }
			    goto add_fb;
			}
		    }
		    /* The other add succeded... */
		    filter = (((int) ebuf[i].udata == ERTS_POLL_KQ_OP_ADD2_W)
			      ? EVFILT_READ
			      : EVFILT_WRITE);
		rm_add_fb:
		    { 
			struct kevent kev;
			struct timespec ts = {0, 0};
			EV_SET(&kev, fd, filter, EV_DELETE, 0, 0, 0);
			(void) kevent(ps->kp_fd, &kev, 1, NULL, 0, &ts);
		    }

		add_fb:
		    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_USEFLBCK;
		    ASSERT(ps->fds_status[fd].used_events);
		    ps->fds_status[fd].used_events = 0;
		    erts_smp_atomic_dec(&ps->no_of_user_fds);
		    update_fallback_pollset(ps, fd);
		    ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
		    break;
		}
		default:
		    fatal_error("%s:%d:write_batch_buf(): Internal error",
				__FILE__, __LINE__);
		    break;
		}
	    }
	}
    }
    bbp->len = 0;
}

#endif /* ERTS_POLL_USE_KQUEUE */

static ERTS_INLINE void
batch_update_pollset(ErtsPollSet ps, int fd, ErtsPollBatchBuf *bbp)
{
    int buf_len;
#if ERTS_POLL_USE_DEVPOLL
    short events;
    struct pollfd *buf;
#elif ERTS_POLL_USE_KQUEUE
    struct kevent *buf;
#endif

#ifdef ERTS_POLL_DEBUG_PRINT
    erts_printf("Doing lazy update on fd=%d\n", fd);
#endif

    if (!need_update(ps, fd))
	return;

    /* Make sure we have room for at least maximum no of entries
       per fd */
    if (bbp->size - bbp->len < 2)
	write_batch_buf(ps, bbp);

    buf_len = bbp->len;
    buf = bbp->buf;

    ASSERT(fd < ps->fds_status_len);

#if ERTS_POLL_USE_DEVPOLL
    events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
    if (!events) {
	buf[buf_len].events = POLLREMOVE;
	erts_smp_atomic_dec(&ps->no_of_user_fds);
    }
    else if (!ps->fds_status[fd].used_events) {
	buf[buf_len].events = events;
	erts_smp_atomic_inc(&ps->no_of_user_fds);
    }
    else {
	if ((ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)
	    || (ps->fds_status[fd].used_events & ~events)) {
	    /* Reset or removed events... */
	    buf[buf_len].fd = fd;
	    buf[buf_len].events = POLLREMOVE;
	    buf[buf_len++].revents = 0;
	}
	buf[buf_len].events = events;
    }
    buf[buf_len].fd = fd;
    buf[buf_len++].revents = 0;

#elif ERTS_POLL_USE_KQUEUE

    if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK) {
	if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_USEFLBCK)
	    update_fallback_pollset(ps, fd);
	else { /* Remove from fallback and try kqueue */
	    ErtsPollEvents events = ps->fds_status[fd].events;
	    ps->fds_status[fd].events = (ErtsPollEvents) 0;
	    update_fallback_pollset(ps, fd);
	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
	    if (events) {
		ps->fds_status[fd].events = events;
		goto try_kqueue;
	    }
	}
    }
    else {
	ErtsPollEvents events, used_events;
	int mod_w, mod_r;
    try_kqueue:
	events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
	used_events = ERTS_POLL_EV_E2N(ps->fds_status[fd].used_events);
	if (!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)) {
	    if (!used_events &&
		(events & ERTS_POLL_EV_IN) && (events & ERTS_POLL_EV_OUT))
		goto do_add_rw;
	    mod_r = ((events & ERTS_POLL_EV_IN)
		     != (used_events & ERTS_POLL_EV_IN));
	    mod_w = ((events & ERTS_POLL_EV_OUT)
		     != (used_events & ERTS_POLL_EV_OUT));
	    goto do_mod;
	}
	else { /* Reset */
	    if ((events & ERTS_POLL_EV_IN) && (events & ERTS_POLL_EV_OUT)) {
	    do_add_rw:
		EV_SET(&buf[buf_len], fd, EVFILT_READ, EV_ADD,
		       0, 0, (void *) ERTS_POLL_KQ_OP_ADD2_R);
		buf_len++;
		EV_SET(&buf[buf_len], fd, EVFILT_WRITE, EV_ADD,
		       0, 0, (void *) ERTS_POLL_KQ_OP_ADD2_W);
		buf_len++;

	    }
	    else {
		mod_r = 1;
		mod_w = 1;
	    do_mod:
		if (mod_r) {
		    if (events & ERTS_POLL_EV_IN) {
			EV_SET(&buf[buf_len], fd, EVFILT_READ, EV_ADD,
			       0, 0, (void *) ERTS_POLL_KQ_OP_ADD_R);
			buf_len++;
		    }
		    else if (used_events & ERTS_POLL_EV_IN) {
			EV_SET(&buf[buf_len], fd, EVFILT_READ, EV_DELETE,
			       0, 0, (void *) ERTS_POLL_KQ_OP_DEL_R);
			buf_len++;
		    }
		}
		if (mod_w) {
		    if (events & ERTS_POLL_EV_OUT) {
			EV_SET(&buf[buf_len], fd, EVFILT_WRITE, EV_ADD,
			       0, 0, (void *) ERTS_POLL_KQ_OP_ADD_W);
			buf_len++;
		    }
		    else if (used_events & ERTS_POLL_EV_OUT) {
			EV_SET(&buf[buf_len], fd, EVFILT_WRITE, EV_DELETE,
			       0, 0, (void *) ERTS_POLL_KQ_OP_DEL_W);
			buf_len++;
		    }
		}
	    }
	}
	if (used_events) {
	    if (!events) {
		erts_smp_atomic_dec(&ps->no_of_user_fds);
	    }
	}
	else {
	    if (events)
		erts_smp_atomic_inc(&ps->no_of_user_fds);
	}
	ASSERT((events & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) == 0);
	ASSERT((used_events & ~(ERTS_POLL_EV_IN|ERTS_POLL_EV_OUT)) == 0);
    }	    

#endif

    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
    ps->fds_status[fd].used_events = ps->fds_status[fd].events;

    bbp->len = buf_len;
}

#else /* !ERTS_POLL_USE_BATCH_UPDATE_POLLSET */

#if ERTS_POLL_USE_EPOLL
static int
#if ERTS_POLL_USE_CONCURRENT_UPDATE
conc_update_pollset(ErtsPollSet ps, int fd, int *update_fallback)
#else
update_pollset(ErtsPollSet ps, int fd)
#endif
{
    int res;
    int op;
    struct epoll_event epe_templ;
    struct epoll_event epe;

    ASSERT(fd < ps->fds_status_len);

    if (!need_update(ps, fd))
	return 0;

#ifdef ERTS_POLL_DEBUG_PRINT
    erts_printf("Doing update on fd=%d\n", fd);
#endif
    if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK) {
#if ERTS_POLL_USE_CONCURRENT_UPDATE
	if (!*update_fallback) {
	    *update_fallback = 1;
	    return 0;
	}
#endif
	if (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_USEFLBCK) {
	    return update_fallback_pollset(ps, fd);
	}
	else { /* Remove from fallback and try epoll */
	    ErtsPollEvents events = ps->fds_status[fd].events;
	    ps->fds_status[fd].events = (ErtsPollEvents) 0;
	    res = update_fallback_pollset(ps, fd);
	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
	    if (!events)
		return res;
	    ps->fds_status[fd].events = events;
	}
    }

    epe_templ.events = ERTS_POLL_EV_E2N(ps->fds_status[fd].events);
    epe_templ.data.fd = fd;

#ifdef VALGRIND
    /* Silence invalid valgrind warning ... */
    memset((void *) &epe.data, 0, sizeof(epoll_data_t));
#endif

    if (epe_templ.events && ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST) {
	do {
	    /* We init 'epe' every time since epoll_ctl() may modify it
	       (not declared const and not documented as const). */
	    epe.events = epe_templ.events;
	    epe.data.fd = epe_templ.data.fd;
	    res = epoll_ctl(ps->kp_fd, EPOLL_CTL_DEL, fd, &epe);
	} while (res != 0 && errno == EINTR);
	erts_smp_atomic_dec(&ps->no_of_user_fds);
	ps->fds_status[fd].used_events = 0;
    }

    if (!epe_templ.events) {
	/* A note on EPOLL_CTL_DEL: linux kernel versions before 2.6.9
	   need a non-NULL event pointer even though it is ignored... */
	op = EPOLL_CTL_DEL;
	erts_smp_atomic_dec(&ps->no_of_user_fds);
    }
    else if (!ps->fds_status[fd].used_events) {
	op = EPOLL_CTL_ADD;
	erts_smp_atomic_inc(&ps->no_of_user_fds);
    }
    else {
	op = EPOLL_CTL_MOD;
    }

    do {
	/* We init 'epe' every time since epoll_ctl() may modify it
	   (not declared const and not documented as const). */
	epe.events = epe_templ.events;
	epe.data.fd = epe_templ.data.fd;
	res = epoll_ctl(ps->kp_fd, op, fd, &epe);
    } while (res != 0 && errno == EINTR);

#if defined(ERTS_POLL_DEBUG_PRINT) && 1
    {
	int saved_errno = errno;
	erts_printf("%s = epoll_ctl(%d, %s, %d, {Ox%x, %d})\n",
		     res == 0 ? "0" : erl_errno_id(errno),
		     ps->kp_fd,
		     (op == EPOLL_CTL_ADD
		      ? "EPOLL_CTL_ADD"
		      : (op == EPOLL_CTL_MOD
			 ? "EPOLL_CTL_MOD"
			 : (op == EPOLL_CTL_DEL
			    ? "EPOLL_CTL_DEL"
			    : "UNKNOWN"))),
		     fd,
		     epe_templ.events,
		     fd);
	errno = saved_errno;
    }
#endif
    if (res == 0)
	ps->fds_status[fd].used_events = ps->fds_status[fd].events;
    else {
	switch (op) {
	case EPOLL_CTL_MOD:
	    epe.events = 0;
	    do {
		/* We init 'epe' every time since epoll_ctl() may modify it
		   (not declared const and not documented as const). */
		epe.events = 0;
		epe.data.fd = fd;
		res = epoll_ctl(ps->kp_fd, EPOLL_CTL_DEL, fd, &epe);
	    } while (res != 0 && errno == EINTR);
	    ps->fds_status[fd].used_events = 0;
	/* Fall through ... */
	case EPOLL_CTL_ADD: {
	    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_USEFLBCK;
	    erts_smp_atomic_dec(&ps->no_of_user_fds);
#if ERTS_POLL_USE_CONCURRENT_UPDATE
	    if (!*update_fallback) {
		*update_fallback = 1;
		return 0;
	    }
#endif
	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
	    res = update_fallback_pollset(ps, fd);
	    ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
	    break;
	}
	case EPOLL_CTL_DEL: {
	    /*
	     * Since we use a lazy update approach EPOLL_CTL_DEL will
	     * frequently fail. This since epoll automatically removes
	     * a filedescriptor that is closed from the poll set.
	     */
	    ps->fds_status[fd].used_events = 0;
	    res = 0;
	    break;
	}
	default:
	    fatal_error("%s:%d:update_pollset(): Internal error\n",
			__FILE__, __LINE__);
	    break;
	}
    }
    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
    return res;
}

#if ERTS_POLL_USE_CONCURRENT_UPDATE
static int
update_pollset(ErtsPollSet ps, int fd)
{
    int update_fallback = 1;
    return conc_update_pollset(ps, fd, &update_fallback);
}
#endif

#endif /* ERTS_POLL_USE_EPOLL */

#endif /* ERTS_POLL_USE_BATCH_UPDATE_POLLSET */

#if ERTS_POLL_USE_POLL || ERTS_POLL_USE_SELECT || ERTS_POLL_USE_FALLBACK

#if ERTS_POLL_USE_FALLBACK
static int update_fallback_pollset(ErtsPollSet ps, int fd)
#else
static int update_pollset(ErtsPollSet ps, int fd)
#endif
{
#ifdef ERTS_POLL_DEBUG_PRINT
#if ERTS_POLL_USE_FALLBACK
    erts_printf("Doing fallback update on fd=%d\n", fd);
#else
    erts_printf("Doing update on fd=%d\n", fd);
#endif
#endif

    ASSERT(fd < ps->fds_status_len);
#if ERTS_POLL_USE_FALLBACK
    ASSERT(ps->fds_status[fd].used_events
	   ? (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK)
	   : (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_USEFLBCK));
#endif

    if (!need_update(ps, fd))
	return 0;

#if ERTS_POLL_USE_FALLBACK
    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_RST;
#endif

#if ERTS_POLL_USE_POLL	/* --- poll -------------------------------- */
    if (!ps->fds_status[fd].events) {
	int pix = ps->fds_status[fd].pix;
	int last_pix;
	if (pix < 0) {
#if ERTS_POLL_USE_FALLBACK
	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
#endif
	    return -1;
	}
#if ERTS_POLL_USE_FALLBACK
	ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
#endif
	erts_smp_atomic_dec(&ps->no_of_user_fds);
	last_pix = --ps->no_poll_fds;
	if (pix != last_pix) {
	/* Move last pix to this pix */
	    ps->poll_fds[pix].fd = ps->poll_fds[last_pix].fd;
	    ps->poll_fds[pix].events = ps->poll_fds[last_pix].events;
	    ps->poll_fds[pix].revents = ps->poll_fds[last_pix].revents;
	    ps->fds_status[ps->poll_fds[pix].fd].pix = pix;
	}
	/* Clear last pix */
	ps->poll_fds[last_pix].fd = -1;
	ps->poll_fds[last_pix].events = (short) 0;
	ps->poll_fds[last_pix].revents = (short) 0;
	/* Clear this fd status */
	ps->fds_status[fd].pix = -1;
	ps->fds_status[fd].used_events = (ErtsPollEvents) 0;
#if ERTS_POLL_USE_FALLBACK
	ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INFLBCK;
#endif
    }
    else {
	int pix = ps->fds_status[fd].pix;
	if (pix < 0) {
#if ERTS_POLL_USE_FALLBACK
	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK)
		    || fd == ps->kp_fd);
#endif
	    erts_smp_atomic_inc(&ps->no_of_user_fds);
	    ps->fds_status[fd].pix = pix = ps->no_poll_fds++;
	    if (pix >= ps->poll_fds_len)
		grow_poll_fds(ps, pix);
	    ps->poll_fds[pix].fd = fd;
	    ps->fds_status[fd].pix = pix;
#if ERTS_POLL_USE_FALLBACK
	    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INFLBCK;
#endif
	}

#if ERTS_POLL_USE_FALLBACK
	ASSERT(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK);
#endif

	/* Events to be used in next poll */
	ps->poll_fds[pix].events = ev2pollev(ps->fds_status[fd].events);
	if (ps->poll_fds[pix].revents) {
	    /* Remove result events that we should not poll for anymore */
	    ps->poll_fds[pix].revents
		&= ev2pollev(~(~ps->fds_status[fd].used_events
			       & ps->fds_status[fd].events));
	}
	/* Save events to be used in next poll */
	ps->fds_status[fd].used_events = ps->fds_status[fd].events;
    }
    return 0;
#elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
    {
	ErtsPollEvents events = ps->fds_status[fd].events;
	if ((ERTS_POLL_EV_IN & events)
	    != (ERTS_POLL_EV_IN & ps->fds_status[fd].used_events)) {
	    if (ERTS_POLL_EV_IN & events) {
		FD_SET(fd, &ps->input_fds);
	    }
	    else {
		FD_CLR(fd, &ps->input_fds);
	    }
	}
	if ((ERTS_POLL_EV_OUT & events)
	    != (ERTS_POLL_EV_OUT & ps->fds_status[fd].used_events)) {
	    if (ERTS_POLL_EV_OUT & events) {
		FD_SET(fd, &ps->output_fds);
	    }
	    else {
		FD_CLR(fd, &ps->output_fds);
	    }
	}

	if (!ps->fds_status[fd].used_events) {
	    ASSERT(events);
	    erts_smp_atomic_inc(&ps->no_of_user_fds);
#if ERTS_POLL_USE_FALLBACK
	    ps->no_select_fds++;
	    ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_INFLBCK;
#endif
	}
	else if (!events) {
	    ASSERT(ps->fds_status[fd].used_events);
	    erts_smp_atomic_dec(&ps->no_of_user_fds);
	    ps->fds_status[fd].events = events;
#if ERTS_POLL_USE_FALLBACK
	    ps->no_select_fds--;
	    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INFLBCK;
#endif
	}

	ps->fds_status[fd].used_events = events;

	if (events && fd > ps->max_fd)
	    ps->max_fd = fd;
	else if (!events && fd == ps->max_fd) {
	    int max = ps->max_fd;
	    for (max = ps->max_fd; max >= 0; max--)
		if (ps->fds_status[max].used_events)
		    break;
	    ps->max_fd = max;
	}
    }
    return 0;
#endif
}

#endif /* ERTS_POLL_USE_POLL || ERTS_POLL_USE_SELECT || ERTS_POLL_USE_FALLBACK */

#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE

static void
handle_update_requests(ErtsPollSet ps)
{
    ErtsPollSetUpdateRequestsBlock *urqbp = &ps->update_requests;
#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
    ErtsPollBatchBuf bb;
    setup_batch_buf(ps, &bb);
#endif

    while (urqbp) {
	ErtsPollSetUpdateRequestsBlock *free_urqbp = urqbp;
	int i;
	int len = urqbp->len;
	for (i = 0; i < len; i++) {
	    int fd = urqbp->fds[i];
	    ASSERT(fd < ps->fds_status_len);
	    ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_INURQ;
#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
	    batch_update_pollset(ps, fd, &bb);
#else
	    update_pollset(ps, fd);
#endif
	}

	free_urqbp = urqbp;
	urqbp = urqbp->next;

	free_update_requests_block(ps, free_urqbp);

    }

#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
    if (bb.len)
	write_batch_buf(ps, &bb);
#endif

    ps->curr_upd_req_block = &ps->update_requests;

#if ERTS_POLL_USE_DEVPOLL && defined(HARD_DEBUG)
    check_poll_status(ps);
#endif

    ERTS_POLLSET_UNSET_HAVE_UPDATE_REQUESTS(ps);
}

#endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */

static ERTS_INLINE ErtsPollEvents
poll_control(ErtsPollSet ps, int fd, ErtsPollEvents events, int on, int *do_wake)
{
    ErtsPollEvents new_events;

    if (fd < ps->internal_fd_limit || fd >= max_fds) {
	if (fd < 0) {
	    new_events = ERTS_POLL_EV_ERR;
	    goto done;
	}
#if ERTS_POLL_USE_KERNEL_POLL
	if (fd == ps->kp_fd) {
	    new_events = ERTS_POLL_EV_NVAL;
	    goto done;
	}
#endif
#if ERTS_POLL_USE_WAKEUP_PIPE
	if (fd == ps->wake_fds[0] || fd == ps->wake_fds[1]) {
	    new_events = ERTS_POLL_EV_NVAL;
	    goto done;
	}
#endif
    }

    if (fd >= ps->fds_status_len)
	grow_fds_status(ps, fd);

    ASSERT(fd < ps->fds_status_len);

    new_events = ps->fds_status[fd].events;

    if (events == 0) {
	*do_wake = 0;
	goto done;
    }

    if (on)
	new_events |= events;
    else
	new_events &= ~events;

    if (new_events == (ErtsPollEvents) 0) {
#if ERTS_POLL_USE_KERNEL_POLL || defined(ERTS_SMP)
	ps->fds_status[fd].flags |= ERTS_POLL_FD_FLG_RST;
#endif
#if ERTS_POLL_USE_FALLBACK
	ps->fds_status[fd].flags &= ~ERTS_POLL_FD_FLG_USEFLBCK;
#endif
    }

    ps->fds_status[fd].events = new_events;

    if (new_events == ps->fds_status[fd].used_events
#if ERTS_POLL_USE_KERNEL_POLL || defined(ERTS_SMP)
	&& !(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST)
#endif
	) {
	*do_wake = 0;
	goto done;
    }

#if !ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    if (update_pollset(ps, fd) != 0)
	new_events = ERTS_POLL_EV_ERR;
#else /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */

#if ERTS_POLL_USE_CONCURRENT_UPDATE
    if (ERTS_POLLSET_IS_POLLED(ps)) {
	int update_fallback = 0;
	conc_update_pollset(ps, fd, &update_fallback);
	if (!update_fallback) {
	    *do_wake = 0; /* no need to wake kernel poller */
	    goto done;
	}
    }
#endif

    enqueue_update_request(ps, fd);
	
#ifdef ERTS_SMP
    /*
     * If new events have been added, we need to wake up the
     * polling thread, but if events have been removed we don't.
     */
    if ((new_events && (ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_RST))
	|| (~ps->fds_status[fd].used_events & new_events))
	*do_wake = 1;
#endif /* ERTS_SMP */

#endif /* ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE */

 done:
#ifdef ERTS_POLL_DEBUG_PRINT
     erts_printf("0x%x = poll_control(ps, %d, 0x%x, %s) do_wake=%d\n",
		 (int) new_events, fd, (int) events, (on ? "on" : "off"), *do_wake);
#endif
    return new_events;
}

void
ERTS_POLL_EXPORT(erts_poll_controlv)(ErtsPollSet ps,
				     ErtsPollControlEntry pcev[],
				     int len)
{
    int i;
    int do_wake;
    int final_do_wake = 0;

    ERTS_POLLSET_LOCK(ps);

    for (i = 0; i < len; i++) {
	do_wake = 0;
	pcev[i].events = poll_control(ps,
				      pcev[i].fd,
				      pcev[i].events,
				      pcev[i].on,
				      &do_wake);
	final_do_wake |= do_wake;
    }

    ERTS_POLLSET_UNLOCK(ps);

#ifdef ERTS_SMP
    if (final_do_wake)
	wake_poller(ps, 0);
#endif /* ERTS_SMP */

}

ErtsPollEvents
ERTS_POLL_EXPORT(erts_poll_control)(ErtsPollSet ps,
				    ErtsSysFdType fd,
				    ErtsPollEvents events,
				    int on,
				    int* do_wake) /* In: Wake up polling thread */
				                  /* Out: Poller is woken */
{
    ErtsPollEvents res;

    ERTS_POLLSET_LOCK(ps);

    res = poll_control(ps, fd, events, on, do_wake);

    ERTS_POLLSET_UNLOCK(ps);

#ifdef ERTS_SMP
    if (*do_wake) {
	wake_poller(ps, 0);
    }
#endif /* ERTS_SMP */

    return res;
}

/*
 * --- Wait on poll set ------------------------------------------------------
 */

#if ERTS_POLL_USE_KERNEL_POLL

static ERTS_INLINE int
save_kp_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res, int chk_fds_res)
{
    int res = 0;
    int i;
    int n = chk_fds_res < max_res ? chk_fds_res : max_res;
#if ERTS_POLL_USE_WAKEUP_PIPE
    int wake_fd = ps->wake_fds[0];
#endif

    for (i = 0; i < n; i++) {

#if ERTS_POLL_USE_EPOLL		/* --- epoll ------------------------------- */

	if (ps->res_events[i].events) {
	    int fd = ps->res_events[i].data.fd;
	    int ix;
	    ErtsPollEvents revents;
#if ERTS_POLL_USE_WAKEUP_PIPE
	    if (fd == wake_fd) {
		cleanup_wakeup_pipe(ps);
		continue;
	    }
#endif
	    ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
	    /* epoll_wait() can repeat the same fd in result array... */
	    ix = (int) ps->fds_status[fd].res_ev_ix;
	    ASSERT(ix >= 0);
	    if (ix >= res || pr[ix].fd != fd) {
		ix = res;
		pr[ix].fd = fd;
		pr[ix].events = (ErtsPollEvents) 0;
	    }

	    revents = ERTS_POLL_EV_N2E(ps->res_events[i].events);
	    pr[ix].events |= revents;
	    if (revents) {
		if (res == ix) {
		    ps->fds_status[fd].res_ev_ix = (unsigned short) ix;
		    res++;
		}
	    }
	}

#elif ERTS_POLL_USE_KQUEUE	/* --- kqueue ------------------------------ */

	struct kevent *ev;
	int fd;
	int ix;

	ev = &ps->res_events[i];
	fd = (int) ev->ident;
	ASSERT(fd < ps->fds_status_len);
	ASSERT(!(ps->fds_status[fd].flags & ERTS_POLL_FD_FLG_INFLBCK));
	ix = (int) ps->fds_status[fd].res_ev_ix;

	ASSERT(ix >= 0);
	if (ix >= res || pr[ix].fd != fd) {
	    ix = res;
	    pr[ix].fd = (int) ev->ident;
	    pr[ix].events = (ErtsPollEvents) 0;
	}

	if (ev->filter == EVFILT_READ) {
#if ERTS_POLL_USE_WAKEUP_PIPE
	    if (fd == wake_fd) {
		cleanup_wakeup_pipe(ps);
		continue;
	    }
#endif
	    pr[ix].events |= ERTS_POLL_EV_IN;
	}
	else if (ev->filter == EVFILT_WRITE)
	    pr[ix].events |= ERTS_POLL_EV_OUT;
	if (ev->flags & (EV_ERROR|EV_EOF)) {
	    if ((ev->flags & EV_ERROR) && (((int) ev->data) == EBADF))
		pr[ix].events |= ERTS_POLL_EV_NVAL;
	    else
		pr[ix].events |= ERTS_POLL_EV_ERR;
	}
	if (pr[ix].events) {
	    if (res == ix) {
		ps->fds_status[fd].res_ev_ix = (unsigned short) ix;
		res++;
	    }
	}

#elif ERTS_POLL_USE_DEVPOLL	/* --- devpoll ----------------------------- */

	if (ps->res_events[i].revents) {
	    int fd = ps->res_events[i].fd;
	    ErtsPollEvents revents;
#if ERTS_POLL_USE_WAKEUP_PIPE
	    if (fd == wake_fd) {
		cleanup_wakeup_pipe(ps);
		continue;
	    }
#endif
	    revents = ERTS_POLL_EV_N2E(ps->res_events[i].events);
	    pr[res].fd = fd;
	    pr[res].events = revents;
	    res++;
	}

#endif

    }

    return res;
}

#endif /* ERTS_POLL_USE_KERNEL_POLL */

#if ERTS_POLL_USE_FALLBACK

static int
get_kp_results(ErtsPollSet ps, ErtsPollResFd pr[], int max_res)
{
    int res;
#if ERTS_POLL_USE_KQUEUE
    struct timespec ts = {0, 0};
#endif

    if (max_res > ps->res_events_len)
	grow_res_events(ps, max_res);

    do {
#if ERTS_POLL_USE_EPOLL
	res = epoll_wait(ps->kp_fd, ps->res_events, max_res, 0);
#elif ERTS_POLL_USE_KQUEUE
	res = kevent(ps->kp_fd, NULL, 0, ps->res_events, max_res, &ts);
#endif
    } while (res < 0 && errno == EINTR);

    if (res < 0) {
	fatal_error("%s:%d: %s() failed: %s (%d)\n",
		    __FILE__, __LINE__,
#if ERTS_POLL_USE_EPOLL
		    "epoll_wait",
#elif ERTS_POLL_USE_KQUEUE
		    "kevent",
#endif
		    erl_errno_id(errno), errno);
    }

    return save_kp_result(ps, pr, max_res, res);
}

#endif /* ERTS_POLL_USE_FALLBACK */



static ERTS_INLINE int
save_poll_result(ErtsPollSet ps, ErtsPollResFd pr[], int max_res,
		 int chk_fds_res, int ebadf)
{
#if ERTS_POLL_USE_DEVPOLL
    return save_kp_result(ps, pr, max_res, chk_fds_res);
#elif ERTS_POLL_USE_FALLBACK
    if (!ps->fallback_used)
	return save_kp_result(ps, pr, max_res, chk_fds_res);
    else
#endif /* ERTS_POLL_USE_FALLBACK */
    {

#if ERTS_POLL_USE_POLL	/* --- poll -------------------------------- */
	int res = 0;
#if ERTS_POLL_USE_WAKEUP_PIPE && !ERTS_POLL_USE_FALLBACK 
	int wake_fd = ps->wake_fds[0];
#endif
	int i, first_ix, end_ix;

	/*
	 * In order to be somewhat fair, we continue on the poll_fds
	 * index where we stopped last time.
	 */
	first_ix = i = ((ps->next_poll_fds_ix < ps->no_poll_fds)
			? ps->next_poll_fds_ix
			: 0);
	end_ix = ps->no_poll_fds;

	while (1) {
	    while (i < end_ix && res < max_res) {
		if (ps->poll_fds[i].revents != (short) 0) {
		    int fd = ps->poll_fds[i].fd;
		    ErtsPollEvents revents;
#if ERTS_POLL_USE_FALLBACK
		    if (fd == ps->kp_fd) {
			res += get_kp_results(ps, &pr[res], max_res-res);
			i++;
			continue;
		    }
#elif ERTS_POLL_USE_WAKEUP_PIPE
		    if (fd == wake_fd) {
			cleanup_wakeup_pipe(ps);
			i++;
			continue;
		    }
#endif
		    revents = pollev2ev(ps->poll_fds[i].revents);
		    pr[res].fd = fd;
		    pr[res].events = revents;
		    res++;
		}
		i++;
	    }
	    if (res == max_res || i == first_ix)
		break;
	    ASSERT(i == ps->no_poll_fds);
	    i = 0;
	    end_ix = first_ix;
	}

	ps->next_poll_fds_ix = i;
	return res;

#elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
	int res = 0;
#if ERTS_POLL_USE_WAKEUP_PIPE && !ERTS_POLL_USE_FALLBACK 
	int wake_fd = ps->wake_fds[0];
#endif
	int fd, first_fd, end_fd;

	/*
	 * In order to be fair, we continue on the fd where we stopped
	 * last time.
	 */
	first_fd = fd = ps->next_sel_fd <= ps->max_fd ? ps->next_sel_fd : 0;
	end_fd = ps->max_fd + 1;

	if (!ebadf) {
	    while (1) {
		while (fd < end_fd && res < max_res) {

		    pr[res].events = (ErtsPollEvents) 0;
		    if (FD_ISSET(fd, &ps->res_input_fds)) {
#if ERTS_POLL_USE_FALLBACK
			if (fd == ps->kp_fd) {
			    res += get_kp_results(ps, &pr[res], max_res-res);
			    fd++;
			    continue;
			}
#elif ERTS_POLL_USE_WAKEUP_PIPE
			if (fd == wake_fd) {
			    cleanup_wakeup_pipe(ps);
			    fd++;
			    continue;
			}
#endif
			pr[res].events |= ERTS_POLL_EV_IN;
		    }
		    if (FD_ISSET(fd, &ps->res_output_fds))
			pr[res].events |= ERTS_POLL_EV_OUT;
		    if (pr[res].events) {
			pr[res].fd = fd;
			res++;
		    }
		    fd++;
		}
		if (res == max_res || fd == first_fd)
		    break;
		ASSERT(fd == ps->max_fd + 1);
		fd = 0;
		end_fd = first_fd;
	    }
	}
	else {
	    /*
	     * Bad file descriptors in poll set.
	     *
	     * This only happens when running poorly written
	     * drivers. This code could be optimized, but we
	     * don't bother since it should never happen...
	     */
	    while (1) {
		while (fd < end_fd && res < max_res) {
		    if (ps->fds_status[fd].events) {
			int sres;
			fd_set *iset = NULL;
			fd_set *oset = NULL;
			if (ps->fds_status[fd].events & ERTS_POLL_EV_IN) {
			    iset = &ps->res_input_fds;
			    FD_ZERO(iset);
			    FD_SET(fd, iset);
			}
			if (ps->fds_status[fd].events & ERTS_POLL_EV_OUT) {
			    oset = &ps->res_output_fds;
			    FD_ZERO(oset);
			    FD_SET(fd, oset);
			
			}
			do {
			    /* Initiate 'tv' each time;
			       select() may modify it */
			    SysTimeval tv = {0, 0};
			    sres = select(ps->max_fd+1, iset, oset, NULL, &tv);
			} while (sres < 0 && errno == EINTR);
			if (sres < 0) {
#if ERTS_POLL_USE_FALLBACK
			    if (fd == ps->kp_fd) {
				res += get_kp_results(ps,
						      &pr[res],
						      max_res-res);
				fd++;
				continue;
			    }
#elif ERTS_POLL_USE_WAKEUP_PIPE
			    if (fd == wake_fd) {
				cleanup_wakeup_pipe(ps);
				fd++;
				continue;
			    }
#endif
			    pr[res].fd = fd;
			    pr[res].events = ERTS_POLL_EV_NVAL;
			    res++;
			}
			else if (sres > 0) {
			    pr[res].fd = fd;
			    if (iset && FD_ISSET(fd, iset)) {
#if ERTS_POLL_USE_FALLBACK
				if (fd == ps->kp_fd) {
				    res += get_kp_results(ps,
							  &pr[res],
							  max_res-res);
				    fd++;
				    continue;
				}
#elif ERTS_POLL_USE_WAKEUP_PIPE
				if (fd == wake_fd) {
				    cleanup_wakeup_pipe(ps);
				    fd++;
				    continue;
				}
#endif
				pr[res].events |= ERTS_POLL_EV_IN;
			    }
			    if (oset && FD_ISSET(fd, oset)) {
				pr[res].events |= ERTS_POLL_EV_OUT;
			    }
			    ASSERT(pr[res].events);
			    res++;
			}
		    }
		    fd++;
		}
		if (res == max_res || fd == first_fd)
		    break;
		ASSERT(fd == ps->max_fd + 1);
		fd = 0;
		end_fd = first_fd;
	    }
	}
	ps->next_sel_fd = fd;
	return res;
#endif
    }
}

static ERTS_INLINE int
check_fd_events(ErtsPollSet ps, SysTimeval *tv, int max_res, int *ps_locked)
{
    ASSERT(!*ps_locked);
    if (erts_smp_atomic_read(&ps->no_of_user_fds) == 0
	&& tv->tv_usec == 0 && tv->tv_sec == 0) {
	/* Nothing to poll and zero timeout; done... */
	return 0;
    }
    else {
	long timeout = tv->tv_sec*1000 + tv->tv_usec/1000;
	if (timeout > ERTS_AINT32_T_MAX)
	    timeout = ERTS_AINT32_T_MAX;
	ASSERT(timeout >= 0);
	erts_smp_atomic32_set_relb(&ps->timeout, (erts_aint32_t) timeout);
#if ERTS_POLL_USE_FALLBACK
	if (!(ps->fallback_used = ERTS_POLL_NEED_FALLBACK(ps))) {

#if ERTS_POLL_USE_EPOLL		/* --- epoll ------------------------------- */
	    if (timeout > INT_MAX)
		timeout = INT_MAX;
	    if (max_res > ps->res_events_len)
		grow_res_events(ps, max_res);
	    return epoll_wait(ps->kp_fd, ps->res_events, max_res, (int)timeout);
#elif ERTS_POLL_USE_KQUEUE	/* --- kqueue ------------------------------ */
	    struct timespec ts;
	    ts.tv_sec = tv->tv_sec;
	    ts.tv_nsec = tv->tv_usec*1000;
	    if (max_res > ps->res_events_len)
		grow_res_events(ps, max_res);
	    return kevent(ps->kp_fd, NULL, 0, ps->res_events, max_res, &ts);
#endif				/* ----------------------------------------- */

	}
	else /* use fallback (i.e. poll() or select()) */
#endif /* ERTS_POLL_USE_FALLBACK */
	{

#if ERTS_POLL_USE_DEVPOLL	/* --- devpoll ----------------------------- */
	    /*
	     * The ioctl() will fail with EINVAL on Solaris 10 if dp_nfds
	     * is set too high. dp_nfds should not be set greater than
	     * the maximum number of file descriptors in the poll set.
	     */
	    struct dvpoll poll_res;
	    int nfds = (int) erts_smp_atomic_read(&ps->no_of_user_fds);
#ifdef ERTS_SMP
	    nfds++; /* Wakeup pipe */
#endif
	    if (timeout > INT_MAX)
		timeout = INT_MAX;
	    poll_res.dp_nfds = nfds < max_res ? nfds : max_res;
	    if (poll_res.dp_nfds > ps->res_events_len)
		grow_res_events(ps, poll_res.dp_nfds);
	    poll_res.dp_fds = ps->res_events;
	    poll_res.dp_timeout = (int) timeout;
	    return ioctl(ps->kp_fd, DP_POLL, &poll_res);
#elif ERTS_POLL_USE_POLL	/* --- poll -------------------------------- */
	    if (timeout > INT_MAX)
		timeout = INT_MAX;
	    return poll(ps->poll_fds, ps->no_poll_fds, (int) timeout);
#elif ERTS_POLL_USE_SELECT	/* --- select ------------------------------ */
	    int res;
	    ps->res_input_fds = ps->input_fds;
	    ps->res_output_fds = ps->output_fds;
	    res = select(ps->max_fd + 1,
			 &ps->res_input_fds,
			 &ps->res_output_fds,
			 NULL,
			 tv);
#ifdef ERTS_SMP
	    if (res < 0
		&& errno == EBADF
		&& ERTS_POLLSET_HAVE_UPDATE_REQUESTS(ps)) {
		/*
		 * This may have happened because another thread deselected
		 * a fd in our poll set and then closed it, i.e. the driver
		 * behaved correctly. We wan't to avoid looking for a bad
		 * fd, that may even not exist anymore. Therefore, handle
		 * update requests and try again.
		 *
		 * We don't know how much of the timeout is left; therfore,
		 * we use a zero timeout. If no error occur and no events
		 * have triggered, we fake an EAGAIN error and let the caller
		 * restart us.
		 */
		SysTimeval zero_tv = {0, 0};
		*ps_locked = 1;
		ERTS_POLLSET_LOCK(ps);
		handle_update_requests(ps);
		res = select(ps->max_fd + 1,
			     &ps->res_input_fds,
			     &ps->res_output_fds,
			     NULL,
			     &zero_tv);
		if (res == 0) {
		    errno = EAGAIN;
		    res = -1;
		}
	    }
#endif /* ERTS_SMP */
	    return res;
#endif				/* ----------------------------------------- */
	}
    }
}

int
ERTS_POLL_EXPORT(erts_poll_wait)(ErtsPollSet ps,
				 ErtsPollResFd pr[],
				 int *len,
				 SysTimeval *utvp)
{
    int res, no_fds;
    int ebadf = 0;
    int ps_locked;
    SysTimeval *tvp;
    SysTimeval itv;

    no_fds = *len;
#ifdef ERTS_POLL_MAX_RES
    if (no_fds >= ERTS_POLL_MAX_RES)
	no_fds = ERTS_POLL_MAX_RES;
#endif

    *len = 0;

    ASSERT(utvp);

    tvp = utvp;

#ifdef ERTS_POLL_DEBUG_PRINT
    erts_printf("Entering erts_poll_wait(), timeout=%d\n",
		 (int) tv->tv_sec*1000 + tv->tv_usec/1000);
#endif

    if (ERTS_POLLSET_SET_POLLED_CHK(ps)) {
	res = EINVAL; /* Another thread is in erts_poll_wait()
			 on this pollset... */
	goto done;
    }

    if (is_woken(ps)) {
	/* Use zero timeout */
	itv.tv_sec = 0;
	itv.tv_usec = 0;
	tvp = &itv;
    }

#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    if (ERTS_POLLSET_HAVE_UPDATE_REQUESTS(ps)) {
	ERTS_POLLSET_LOCK(ps);
	handle_update_requests(ps);
	ERTS_POLLSET_UNLOCK(ps);
    }
#endif

    ps_locked = 0;
    res = check_fd_events(ps, tvp, no_fds, &ps_locked);

    woke_up(ps);

    if (res == 0) {
	res = ETIMEDOUT;
    }
    else if (res < 0) {
#if ERTS_POLL_USE_SELECT
	if (errno == EBADF) {
	    ebadf = 1;
	    goto save_results;
	}
#endif
	res = errno;
    }
    else {
#if ERTS_POLL_USE_SELECT
    save_results:
#endif

#ifdef ERTS_SMP
	if (!ps_locked) {
	    ps_locked = 1;
	    ERTS_POLLSET_LOCK(ps);
	}
#endif

	no_fds = save_poll_result(ps, pr, no_fds, res, ebadf);

#ifdef HARD_DEBUG
	check_poll_result(pr, no_fds);
#endif

	res = (no_fds == 0 ? (is_interrupted_reset(ps) ? EINTR : EAGAIN) : 0);
	*len = no_fds;
    }

#ifdef ERTS_SMP
    if (ps_locked)
	ERTS_POLLSET_UNLOCK(ps);
    ERTS_POLLSET_UNSET_POLLED(ps);
#endif

 done:
    erts_smp_atomic32_set_relb(&ps->timeout, ERTS_AINT32_T_MAX);
#ifdef ERTS_POLL_DEBUG_PRINT
    erts_printf("Leaving %s = erts_poll_wait()\n",
		 res == 0 ? "0" : erl_errno_id(res));
#endif

    return res;
}

/*
 * --- Interrupt a thread doing erts_poll_wait() -----------------------------
 */

void
ERTS_POLL_EXPORT(erts_poll_interrupt)(ErtsPollSet ps, int set)
{
#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP)
    /*
     * NOTE: This function might be called from signal handlers in the
     *       non-smp case; therefore, it has to be async-signal safe in
     *       the non-smp case.
     */
    if (!set)
	reset_wakeup_state(ps);
    else
	wake_poller(ps, 1);
#endif
}

/*
 * erts_poll_interrupt_timed():
 *   If 'set' != 0, interrupt thread blocked in erts_poll_wait() if it
 * is not guaranteed that it will timeout before 'msec' milli seconds.
 */
void
ERTS_POLL_EXPORT(erts_poll_interrupt_timed)(ErtsPollSet ps,
					    int set,
					    long msec)
{
#if ERTS_POLL_ASYNC_INTERRUPT_SUPPORT || defined(ERTS_SMP)
    if (!set)
	reset_wakeup_state(ps);
    else {
	if (erts_smp_atomic32_read_acqb(&ps->timeout) > (erts_aint32_t) msec)
	    wake_poller(ps, 1);
#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
	else {
	    if (ERTS_POLLSET_IS_POLLED(ps))
		erts_smp_atomic_inc(&ps->no_avoided_wakeups);
	    erts_smp_atomic_inc(&ps->no_avoided_interrupts);
	}
	erts_smp_atomic_inc(&ps->no_interrupt_timed);
#endif
    }
#endif
}

int
ERTS_POLL_EXPORT(erts_poll_max_fds)(void)
{
    return max_fds;
}
/*
 * --- Initialization --------------------------------------------------------
 */

#ifdef VXWORKS
extern int erts_vxworks_max_files;
#endif

void
ERTS_POLL_EXPORT(erts_poll_init)(void)
{
    erts_smp_spinlock_init(&pollsets_lock, "pollsets_lock");
    pollsets = NULL;

    errno = 0;

#if defined(VXWORKS)
    max_fds = erts_vxworks_max_files;
#elif !defined(NO_SYSCONF)
    max_fds = sysconf(_SC_OPEN_MAX);
#elif ERTS_POLL_USE_SELECT
    max_fds = NOFILE;
#else
    max_fds = OPEN_MAX;
#endif

#if ERTS_POLL_USE_SELECT && defined(FD_SETSIZE)
    if (max_fds > FD_SETSIZE)
	max_fds = FD_SETSIZE;
#endif

    if (max_fds < 0)
	fatal_error("erts_poll_init(): Failed to get max number of files: %s\n",
		    erl_errno_id(errno));

#ifdef ERTS_POLL_DEBUG_PRINT
    print_misc_debug_info();
#endif
}

ErtsPollSet
ERTS_POLL_EXPORT(erts_poll_create_pollset)(void)
{
#if ERTS_POLL_USE_KERNEL_POLL
    int kp_fd;
#endif
    ErtsPollSet ps = erts_alloc(ERTS_ALC_T_POLLSET,
				sizeof(struct ErtsPollSet_));
    ps->internal_fd_limit = 0;
    ps->fds_status = NULL;
    ps->fds_status_len = 0;
    erts_smp_atomic_init(&ps->no_of_user_fds, 0);
#if ERTS_POLL_USE_KERNEL_POLL
    ps->kp_fd = -1;
#if ERTS_POLL_USE_EPOLL
    kp_fd = epoll_create(256);
    ps->res_events_len = 0;
    ps->res_events = NULL;
#elif ERTS_POLL_USE_DEVPOLL
    kp_fd = open("/dev/poll", O_RDWR);
    ps->res_events_len = 0;
    ps->res_events = NULL;
#elif ERTS_POLL_USE_KQUEUE
    kp_fd = kqueue();
    ps->res_events_len = 0;
    ps->res_events = NULL;
#endif
    if (kp_fd < 0)
	fatal_error("erts_poll_create_pollset(): Failed to "
#if ERTS_POLL_USE_EPOLL
		    "create epoll set"
#elif ERTS_POLL_USE_DEVPOLL
		    "to open /dev/poll"
#elif ERTS_POLL_USE_KQUEUE
		    "create kqueue"
#endif
		    ": %s (%d)\n",
		    erl_errno_id(errno), errno);
#endif /* ERTS_POLL_USE_KERNEL_POLL */
#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
    /* res_events is also used as write buffer */
    grow_res_events(ps, ERTS_POLL_MIN_BATCH_BUF_SIZE);
#endif
#if ERTS_POLL_USE_POLL
    ps->next_poll_fds_ix = 0;
    ps->no_poll_fds = 0;
    ps->poll_fds_len = 0;
    ps->poll_fds = NULL;
#elif ERTS_POLL_USE_SELECT
    ps->next_sel_fd = 0;
    ps->max_fd = -1;
#if ERTS_POLL_USE_FALLBACK
    ps->no_select_fds = 0;
#endif
    FD_ZERO(&ps->input_fds);
    FD_ZERO(&ps->res_input_fds);
    FD_ZERO(&ps->output_fds);
    FD_ZERO(&ps->res_output_fds);
#endif
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    ps->update_requests.next = NULL;
    ps->update_requests.len = 0;
    ps->curr_upd_req_block = &ps->update_requests;
    erts_smp_atomic32_init(&ps->have_update_requests, 0);
#endif
#ifdef ERTS_SMP
    erts_atomic32_init(&ps->polled, 0);
    erts_smp_mtx_init(&ps->mtx, "pollset");
#endif
#ifdef ERTS_SMP
    erts_atomic32_init(&ps->wakeup_state, (erts_aint32_t) 0);
#elif ERTS_POLL_ASYNC_INTERRUPT_SUPPORT
    ps->wakeup_state = 0;
#endif
#if ERTS_POLL_USE_WAKEUP_PIPE
    create_wakeup_pipe(ps);
#endif
#if ERTS_POLL_USE_FALLBACK
    if (kp_fd >= ps->fds_status_len)
	grow_fds_status(ps, kp_fd);
    /* Force kernel poll fd into fallback (poll/select) set */
    ps->fds_status[kp_fd].flags
	|= ERTS_POLL_FD_FLG_INFLBCK|ERTS_POLL_FD_FLG_USEFLBCK;
    {
	int do_wake = 0;
	ERTS_POLL_EXPORT(erts_poll_control)(ps, kp_fd, ERTS_POLL_EV_IN, 1,
					    &do_wake);
    }    
#endif
#if ERTS_POLL_USE_KERNEL_POLL
    if (ps->internal_fd_limit <= kp_fd)
	ps->internal_fd_limit = kp_fd + 1;
    ps->kp_fd = kp_fd;
#endif
    erts_smp_atomic32_init(&ps->timeout, ERTS_AINT32_T_MAX);
#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
    erts_smp_atomic_init(&ps->no_avoided_wakeups, 0);
    erts_smp_atomic_init(&ps->no_avoided_interrupts, 0);
    erts_smp_atomic_init(&ps->no_interrupt_timed, 0);
#endif
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    handle_update_requests(ps);
#endif
#if ERTS_POLL_USE_FALLBACK
    ps->fallback_used = 0;
#endif
    erts_smp_atomic_set(&ps->no_of_user_fds, 0); /* Don't count wakeup pipe and fallback fd */

    erts_smp_spin_lock(&pollsets_lock);
    ps->next = pollsets;
    pollsets = ps;
    erts_smp_spin_unlock(&pollsets_lock);

    return ps;
}

void
ERTS_POLL_EXPORT(erts_poll_destroy_pollset)(ErtsPollSet ps)
{

    if (ps->fds_status)
	erts_free(ERTS_ALC_T_FD_STATUS, (void *) ps->fds_status);

#if ERTS_POLL_USE_EPOLL
    if (ps->kp_fd >= 0)
	close(ps->kp_fd);
    if (ps->res_events)
	erts_free(ERTS_ALC_T_POLL_RES_EVS, (void *) ps->res_events);
#elif ERTS_POLL_USE_DEVPOLL
    if (ps->kp_fd >= 0)
	close(ps->kp_fd);
    if (ps->res_events)
	erts_free(ERTS_ALC_T_POLL_RES_EVS, (void *) ps->res_events);
#elif ERTS_POLL_USE_POLL
    if (ps->poll_fds)
	erts_free(ERTS_ALC_T_POLL_FDS, (void *) ps->poll_fds);
#elif ERTS_POLL_USE_SELECT
#endif
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    {
	ErtsPollSetUpdateRequestsBlock *urqbp = ps->update_requests.next;
	while (urqbp) {
	    ErtsPollSetUpdateRequestsBlock *free_urqbp = urqbp;
	    urqbp = urqbp->next;
	    free_update_requests_block(ps, free_urqbp);
	}
    }
#endif
#ifdef ERTS_SMP
    erts_smp_mtx_destroy(&ps->mtx);
#endif
#if ERTS_POLL_USE_WAKEUP_PIPE
    if (ps->wake_fds[0] >= 0)
	close(ps->wake_fds[0]);
    if (ps->wake_fds[1] >= 0)
	close(ps->wake_fds[1]);
#endif

    erts_smp_spin_lock(&pollsets_lock);
    if (ps == pollsets)
	pollsets = pollsets->next;
    else {
	ErtsPollSet prev_ps;
	for (prev_ps = pollsets; ps != prev_ps->next; prev_ps = prev_ps->next);
	ASSERT(ps == prev_ps->next);
	prev_ps->next = ps->next;
    }
    erts_smp_spin_unlock(&pollsets_lock);

    erts_free(ERTS_ALC_T_POLLSET, (void *) ps);
}

/*
 * --- Info ------------------------------------------------------------------
 */

void
ERTS_POLL_EXPORT(erts_poll_info)(ErtsPollSet ps, ErtsPollInfo *pip)
{
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    int pending_updates;
#endif
    Uint size = 0;

    ERTS_POLLSET_LOCK(ps);

    size += sizeof(struct ErtsPollSet_);
    size += ps->fds_status_len*sizeof(ErtsFdStatus);

#if ERTS_POLL_USE_EPOLL
    size += ps->res_events_len*sizeof(struct epoll_event);
#elif ERTS_POLL_USE_DEVPOLL
    size += ps->res_events_len*sizeof(struct pollfd);
#elif ERTS_POLL_USE_KQUEUE
    size += ps->res_events_len*sizeof(struct kevent);
#endif

#if ERTS_POLL_USE_POLL
    size += ps->poll_fds_len*sizeof(struct pollfd);
#elif ERTS_POLL_USE_SELECT
#endif

#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
    {
	ErtsPollSetUpdateRequestsBlock *urqbp = ps->update_requests.next;
	pending_updates = ps->update_requests.len;
	while (urqbp) {
	    size += sizeof(ErtsPollSetUpdateRequestsBlock);
	    pending_updates += urqbp->len;
	    urqbp = urqbp->next;
	}
    }
#endif

    pip->primary = 
#if ERTS_POLL_USE_KQUEUE
	"kqueue"
#elif ERTS_POLL_USE_EPOLL
	"epoll"
#elif ERTS_POLL_USE_DEVPOLL
	"/dev/poll"
#elif ERTS_POLL_USE_POLL
	"poll"
#elif ERTS_POLL_USE_SELECT
	"select"
#endif
	;

    pip->fallback = 
#if !ERTS_POLL_USE_FALLBACK
	NULL
#elif ERTS_POLL_USE_POLL
	"poll"
#elif ERTS_POLL_USE_SELECT
	"select"
#endif
	;

    pip->kernel_poll = 
#if !ERTS_POLL_USE_KERNEL_POLL
	NULL
#elif ERTS_POLL_USE_KQUEUE
	"kqueue"
#elif ERTS_POLL_USE_EPOLL
	"epoll"
#elif ERTS_POLL_USE_DEVPOLL
	"/dev/poll"
#endif
	;

    pip->memory_size = size;

    pip->poll_set_size = (int) erts_smp_atomic_read(&ps->no_of_user_fds);
#ifdef ERTS_SMP
    pip->poll_set_size++; /* Wakeup pipe */
#endif

    pip->fallback_poll_set_size =
#if !ERTS_POLL_USE_FALLBACK
	0
#elif ERTS_POLL_USE_POLL
	ps->no_poll_fds
#elif ERTS_POLL_USE_SELECT
	ps->no_select_fds
#endif
	;

#if ERTS_POLL_USE_FALLBACK
    /* If only kp_fd is in fallback poll set we don't use fallback... */
    if (pip->fallback_poll_set_size == 1)
	pip->fallback_poll_set_size = 0;
    else
	pip->poll_set_size++; /* kp_fd */
#endif

    pip->lazy_updates =
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
	1
#else
	0
#endif
	;

    pip->pending_updates = 
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
	pending_updates
#else
	0
#endif
	;

    pip->batch_updates = 
#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
	1
#else
	0
#endif
	;

    pip->concurrent_updates =
#if ERTS_POLL_USE_CONCURRENT_UPDATE
	1
#else
	0
#endif
	;

    pip->max_fds = max_fds;

#ifdef ERTS_POLL_COUNT_AVOIDED_WAKEUPS
    pip->no_avoided_wakeups = erts_smp_atomic_read(&ps->no_avoided_wakeups);
    pip->no_avoided_interrupts = erts_smp_atomic_read(&ps->no_avoided_interrupts);
    pip->no_interrupt_timed = erts_smp_atomic_read(&ps->no_interrupt_timed);
#endif

    ERTS_POLLSET_UNLOCK(ps);

}

/*
 * Fatal error...
 */

#ifndef ERTS_GOT_SIGUSR1
#  define ERTS_GOT_SIGUSR1 0
#endif

static void
fatal_error(char *format, ...)
{
    va_list ap;

    if (ERTS_IS_CRASH_DUMPING || ERTS_GOT_SIGUSR1) {
	/*
	 * Crash dump writing and reception of sigusr1 (which will
	 * result in a crash dump) closes all file descriptors. This
	 * typically results in a fatal error for erts_poll() (wakeup
	 * pipes and kernel poll fds are closed).
	 *
	 * We ignore the error and let the crash dump writing continue...
	 */
	return;
    }
    va_start(ap, format);
    erts_vfprintf(stderr, format, ap);
    va_end(ap);
    abort();
}

static void
fatal_error_async_signal_safe(char *error_str)
{
    if (ERTS_IS_CRASH_DUMPING || ERTS_GOT_SIGUSR1) {
	/* See comment above in fatal_error() */
	return;
    }
    if (error_str) {
	int len = 0;
	while (error_str[len])
	    len++;
	if (len) {
	    /* async signal safe */
	    erts_silence_warn_unused_result(write(2, error_str, len));
	}
    }
    abort();
}
 
/*
 * --- Debug -----------------------------------------------------------------
 */

void
ERTS_POLL_EXPORT(erts_poll_get_selected_events)(ErtsPollSet ps,
						ErtsPollEvents ev[],
						int len)
{
    int fd;
    ERTS_POLLSET_LOCK(ps);
    for (fd = 0; fd < len; fd++) {
	if (fd >= ps->fds_status_len)
	    ev[fd] = 0;
	else {
	    ev[fd] = ps->fds_status[fd].events;
#if ERTS_POLL_USE_WAKEUP_PIPE
	    if (fd == ps->wake_fds[0] || fd == ps->wake_fds[1])
		ev[fd] |= ERTS_POLL_EV_NVAL;
#endif
#if ERTS_POLL_USE_KERNEL_POLL
	    if (fd == ps->kp_fd)
		ev[fd] |= ERTS_POLL_EV_NVAL;
#endif
	}
    }
    ERTS_POLLSET_UNLOCK(ps);

}

#ifdef HARD_DEBUG

static void
check_poll_result(ErtsPollResFd pr[], int len)
{
    int i, j;

    for (i = 0; i < len; i++) {
	ASSERT(pr[i].fd >= 0);
	ASSERT(pr[i].fd < max_fds);
	for (j = 0; j < len; j++) {
	    ASSERT(i == j || pr[i].fd != pr[j].fd);
	}
    }
}


#if ERTS_POLL_USE_DEVPOLL

static void
check_poll_status(ErtsPollSet ps)
{
    int i;
    for (i = 0; i < ps->fds_status_len; i++) {
	int ires;
	struct pollfd dp_fd;
	short events = ERTS_POLL_EV_E2N(ps->fds_status[i].events);
	
	dp_fd.fd = i;
	dp_fd.events = (short) 0;
	dp_fd.revents = (short) 0;

	ires = ioctl(ps->kp_fd, DP_ISPOLLED, &dp_fd);

	if (ires == 0) {
	    ASSERT(!events);
	}
	else if (ires == 1) {
	    ASSERT(events);
	    ASSERT(events == dp_fd.revents);
	}
	else {
	    ASSERT(0);
	}
	ASSERT(dp_fd.fd == i);
	ASSERT(ps->fds_status[i].events == ps->fds_status[i].used_events);
    }
}

#endif /* ERTS_POLL_USE_DEVPOLL */
#endif /* HARD_DEBUG */

#ifdef ERTS_POLL_DEBUG_PRINT
static void
print_misc_debug_info(void)
{
    erts_printf("erts_poll using: %s lazy_updates:%s batch_updates:%s\n",
#if ERTS_POLL_USE_KQUEUE
		"kqueue"
#elif ERTS_POLL_USE_EPOLL
		"epoll"
#elif ERTS_POLL_USE_DEVPOLL
		"/dev/poll"
#endif
#if ERTS_POLL_USE_FALLBACK
		"-"
#endif
#if ERTS_POLL_USE_POLL
		"poll"
#elif ERTS_POLL_USE_SELECT
		"select"
#endif
		,
#if ERTS_POLL_USE_UPDATE_REQUESTS_QUEUE
		"true"
#else
		"false"
#endif
		,
#if ERTS_POLL_USE_BATCH_UPDATE_POLLSET
		"true"
#else
		"false"
#endif
		);

    erts_printf("ERTS_POLL_EV_IN=0x%x\n"
		"ERTS_POLL_EV_OUT=0x%x\n"
		"ERTS_POLL_EV_NVAL=0x%x\n"
		"ERTS_POLL_EV_ERR=0x%x\n",
		ERTS_POLL_EV_IN,
		ERTS_POLL_EV_OUT,
		ERTS_POLL_EV_NVAL,
		ERTS_POLL_EV_ERR);

#ifdef FD_SETSIZE
    erts_printf("FD_SETSIZE=%d\n", FD_SETSIZE);
#endif
}
    
#endif