summaryrefslogtreecommitdiff
path: root/gdb/event-loop.c
blob: f46fe4df37969780f47e3d143fcaf440633ea5f6 (plain)
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
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
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
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
/* Event loop machinery for GDB, the GNU debugger.
   Copyright 1999 Free Software Foundation, Inc.
   Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA. */

#include "defs.h"
#include "top.h"
#include "event-loop.h"
#include "event-top.h"

#ifdef HAVE_POLL
#if defined (HAVE_POLL_H)
#include <poll.h>
#elif defined (HAVE_SYS_POLL_H)
#include <sys/poll.h>
#endif
#endif

#include <sys/types.h>
#include <string.h>
#include <errno.h>
#include <setjmp.h>
#include <sys/time.h>

/* Type of the mask arguments to select. */

#ifndef HAVE_POLL
#ifdef NO_FD_SET
/* All this stuff below is not required if select is used as God(tm)
   intended, with the FD_* macros.  Are there any implementations of
   select which don't have FD_SET and other standard FD_* macros?  I
   don't think there are, but if I'm wrong, we need to catch them.  */
#error FD_SET must be defined if select function is to be used!

#ifndef _AIX
typedef long fd_mask;
#endif
#if defined(_IBMR2)
#define SELECT_MASK void
#else
#define SELECT_MASK int
#endif /* !_IBMR2 */

/* Define "NBBY" (number of bits per byte) if it's not already defined. */

#ifndef NBBY
#define NBBY 8
#endif

/* Define the number of fd_masks in an fd_set */

#ifndef FD_SETSIZE
#ifdef OPEN_MAX
#define FD_SETSIZE OPEN_MAX
#else
#define FD_SETSIZE 256
#endif
#endif
#if !defined(howmany)
#define howmany(x, y) (((x)+((y)-1))/(y))
#endif
#ifndef NFDBITS
#define NFDBITS NBBY*sizeof(fd_mask)
#endif
#define MASK_SIZE howmany(FD_SETSIZE, NFDBITS)

#endif /* NO_FD_SET */
#endif /* !HAVE_POLL */


typedef struct gdb_event gdb_event;
typedef void (event_handler_func) (int);

/* Event for the GDB event system.  Events are queued by calling
   async_queue_event and serviced later on by gdb_do_one_event. An
   event can be, for instance, a file descriptor becoming ready to be
   read. Servicing an event simply means that the procedure PROC will
   be called.  We have 2 queues, one for file handlers that we listen
   to in the event loop, and one for the file handlers+events that are
   ready. The procedure PROC associated with each event is always the
   same (handle_file_event).  Its duty is to invoke the handler
   associated with the file descriptor whose state change generated
   the event, plus doing other cleanups and such. */

struct gdb_event
  {
    event_handler_func *proc;	/* Procedure to call to service this event. */
    int fd;			/* File descriptor that is ready. */
    struct gdb_event *next_event;	/* Next in list of events or NULL. */
  };

/* Information about each file descriptor we register with the event
   loop. */

typedef struct file_handler
  {
    int fd;			/* File descriptor. */
    int mask;			/* Events we want to monitor: POLLIN, etc. */
    int ready_mask;		/* Events that have been seen since
				   the last time. */
    handler_func *proc;		/* Procedure to call when fd is ready. */
    gdb_client_data client_data;	/* Argument to pass to proc. */
    int error;			/* Was an error detected on this fd? */
    struct file_handler *next_file;	/* Next registered file descriptor. */
  }
file_handler;

/* PROC is a function to be invoked when the READY flag is set. This
   happens when there has been a signal and the corresponding signal
   handler has 'triggered' this async_signal_handler for
   execution. The actual work to be done in response to a signal will
   be carried out by PROC at a later time, within process_event. This
   provides a deferred execution of signal handlers.
   Async_init_signals takes care of setting up such an
   asyn_signal_handler for each interesting signal. */
typedef struct async_signal_handler
  {
    int ready;			/* If ready, call this handler from the main event loop, 
				   using invoke_async_handler. */
    struct async_signal_handler *next_handler;	/* Ptr to next handler */
    sig_handler_func *proc;	/* Function to call to do the work */
    gdb_client_data client_data;	/* Argument to async_handler_func */
  }
async_signal_handler;


/* Event queue:  
   - the first event in the queue is the head of the queue. 
   It will be the next to be serviced.
   - the last event in the queue 

   Events can be inserted at the front of the queue or at the end of
   the queue.  Events will be extracted from the queue for processing
   starting from the head.  Therefore, events inserted at the head of
   the queue will be processed in a last in first out fashion, while
   those inserted at the tail of the queue will be processed in a first
   in first out manner.  All the fields are NULL if the queue is
   empty. */

static struct
  {
    gdb_event *first_event;	/* First pending event */
    gdb_event *last_event;	/* Last pending event */
  }
event_queue;

/* Gdb_notifier is just a list of file descriptors gdb is interested in.
   These are the input file descriptor, and the target file
   descriptor. We have two flavors of the notifier, one for platforms
   that have the POLL function, the other for those that don't, and
   only support SELECT. Each of the elements in the gdb_notifier list is
   basically a description of what kind of events gdb is interested
   in, for each fd. */

/* As of 1999-04-30 only the input file descriptor is registered with the
   event loop. */

/* Do we use poll or select ? */
#ifdef HAVE_POLL
#define USE_POLL 1
#else
#define USE_POLL 0
#endif /* HAVE_POLL */

static unsigned char use_poll = USE_POLL;

static struct
  {
    /* Ptr to head of file handler list. */
    file_handler *first_file_handler;

#ifdef HAVE_POLL
    /* Ptr to array of pollfd structures. */
    struct pollfd *poll_fds;

    /* Timeout in milliseconds for calls to poll(). */
    int poll_timeout;
#endif

    /* Masks to be used in the next call to select.
       Bits are set in response to calls to create_file_handler. */
    fd_set check_masks[3];

    /* What file descriptors were found ready by select. */
    fd_set ready_masks[3];

    /* Number of file descriptors to monitor. (for poll) */
    /* Number of valid bits (highest fd value + 1). (for select) */
    int num_fds;

    /* Time structure for calls to select(). */
    struct timeval select_timeout;

    /* Flag to tell whether the timeout should be used. */
    int timeout_valid;
  }
gdb_notifier;

/* Structure associated with a timer. PROC will be executed at the
   first occasion after WHEN. */
struct gdb_timer
  {
    struct timeval when;
    int timer_id;
    struct gdb_timer *next;
    timer_handler_func *proc;	/* Function to call to do the work */
    gdb_client_data client_data;	/* Argument to async_handler_func */
  }
gdb_timer;

/* List of currently active timers. It is sorted in order of
   increasing timers. */
static struct
  {
    /* Pointer to first in timer list. */
    struct gdb_timer *first_timer;

    /* Id of the last timer created. */
    int num_timers;
  }
timer_list;

/* All the async_signal_handlers gdb is interested in are kept onto
   this list. */
static struct
  {
    /* Pointer to first in handler list. */
    async_signal_handler *first_handler;

    /* Pointer to last in handler list. */
    async_signal_handler *last_handler;
  }
sighandler_list;

/* Are any of the handlers ready?  Check this variable using
   check_async_ready. This is used by process_event, to determine
   whether or not to invoke the invoke_async_signal_handler
   function. */
static int async_handler_ready = 0;

static void create_file_handler (int fd, int mask, handler_func * proc, gdb_client_data client_data);
static void invoke_async_signal_handler (void);
static void handle_file_event (int event_file_desc);
static int gdb_wait_for_event (void);
static int gdb_do_one_event (void *data);
static int check_async_ready (void);
static void async_queue_event (gdb_event * event_ptr, queue_position position);
static gdb_event *create_file_event (int fd);
static int process_event (void);
static void handle_timer_event (int dummy);
static void poll_timers (void);


/* Insert an event object into the gdb event queue at 
   the specified position.
   POSITION can be head or tail, with values TAIL, HEAD.
   EVENT_PTR points to the event to be inserted into the queue.
   The caller must allocate memory for the event. It is freed
   after the event has ben handled.
   Events in the queue will be processed head to tail, therefore,
   events inserted at the head of the queue will be processed
   as last in first out. Event appended at the tail of the queue
   will be processed first in first out. */
static void
async_queue_event (gdb_event * event_ptr, queue_position position)
{
  if (position == TAIL)
    {
      /* The event will become the new last_event. */

      event_ptr->next_event = NULL;
      if (event_queue.first_event == NULL)
	event_queue.first_event = event_ptr;
      else
	event_queue.last_event->next_event = event_ptr;
      event_queue.last_event = event_ptr;
    }
  else if (position == HEAD)
    {
      /* The event becomes the new first_event. */

      event_ptr->next_event = event_queue.first_event;
      if (event_queue.first_event == NULL)
	event_queue.last_event = event_ptr;
      event_queue.first_event = event_ptr;
    }
}

/* Create a file event, to be enqueued in the event queue for
   processing. The procedure associated to this event is always
   handle_file_event, which will in turn invoke the one that was
   associated to FD when it was registered with the event loop. */
static gdb_event *
create_file_event (int fd)
{
  gdb_event *file_event_ptr;

  file_event_ptr = (gdb_event *) xmalloc (sizeof (gdb_event));
  file_event_ptr->proc = handle_file_event;
  file_event_ptr->fd = fd;
  return (file_event_ptr);
}

/* Process one event.
   The event can be the next one to be serviced in the event queue,
   or an asynchronous event handler can be invoked in response to
   the reception of a signal.
   If an event was processed (either way), 1 is returned otherwise
   0 is returned.   
   Scan the queue from head to tail, processing therefore the high
   priority events first, by invoking the associated event handler
   procedure. */
static int
process_event (void)
{
  gdb_event *event_ptr, *prev_ptr;
  event_handler_func *proc;
  int fd;

  /* First let's see if there are any asynchronous event handlers that
     are ready. These would be the result of invoking any of the
     signal handlers. */

  if (check_async_ready ())
    {
      invoke_async_signal_handler ();
      return 1;
    }

  /* Look in the event queue to find an event that is ready
     to be processed. */

  for (event_ptr = event_queue.first_event; event_ptr != NULL;
       event_ptr = event_ptr->next_event)
    {
      /* Call the handler for the event. */

      proc = event_ptr->proc;
      fd = event_ptr->fd;

      /* Let's get rid of the event from the event queue.  We need to
         do this now because while processing the event, the proc
         function could end up calling 'error' and therefore jump out
         to the caller of this function, gdb_do_one_event. In that
         case, we would have on the event queue an event wich has been
         processed, but not deleted. */

      if (event_queue.first_event == event_ptr)
	{
	  event_queue.first_event = event_ptr->next_event;
	  if (event_ptr->next_event == NULL)
	    event_queue.last_event = NULL;
	}
      else
	{
	  prev_ptr = event_queue.first_event;
	  while (prev_ptr->next_event != event_ptr)
	    prev_ptr = prev_ptr->next_event;

	  prev_ptr->next_event = event_ptr->next_event;
	  if (event_ptr->next_event == NULL)
	    event_queue.last_event = prev_ptr;
	}
      free ((char *) event_ptr);

      /* Now call the procedure associated with the event. */
      (*proc) (fd);
      return 1;
    }

  /* this is the case if there are no event on the event queue. */
  return 0;
}

/* Process one high level event.  If nothing is ready at this time,
   wait for something to happen (via gdb_wait_for_event), then process
   it.  Returns >0 if something was done otherwise returns <0 (this
   can happen if there are no event sources to wait for).  If an error
   occurs catch_errors() which calls this function returns zero. */

static int
gdb_do_one_event (void *data)
{
  /* Any events already waiting in the queue? */
  if (process_event ())
    {
      return 1;
    }

  /* Are any timers that are ready? If so, put an event on the queue. */
  poll_timers ();

  /* Wait for a new event.  If gdb_wait_for_event returns -1,
     we should get out because this means that there are no
     event sources left. This will make the event loop stop,
     and the application exit. */

  if (gdb_wait_for_event () < 0)
    {
      return -1;
    }

  /* Handle any new events occurred while waiting. */
  if (process_event ())
    {
      return 1;
    }

  /* If gdb_wait_for_event has returned 1, it means that one
     event has been handled. We break out of the loop. */
  return 1;
}

/* Start up the event loop. This is the entry point to the event loop
   from the command loop. */

void
start_event_loop (void)
{
  /* Loop until there is nothing to do. This is the entry point to the
     event loop engine. gdb_do_one_event, called via catch_errors()
     will process one event for each invocation.  It blocks waits for
     an event and then processes it.  >0 when an event is processed, 0
     when catch_errors() caught an error and <0 when there are no
     longer any event sources registered. */
  while (1)
    {
      int result = catch_errors (gdb_do_one_event, 0, "", RETURN_MASK_ALL);
      if (result < 0)
	break;
      if (result == 0)
	{
	  /* FIXME: this should really be a call to a hook that is
	     interface specific, because interfaces can display the
	     prompt in their own way. */
	  display_gdb_prompt (0);
	  /* Maybe better to set a flag to be checked somewhere as to
	     whether display the prompt or not. */
	}
    }

  /* We are done with the event loop. There are no more event sources
     to listen to.  So we exit GDB. */
  return;
}


/* Wrapper function for create_file_handler, so that the caller
   doesn't have to know implementation details about the use of poll
   vs. select. */
void
add_file_handler (int fd, handler_func * proc, gdb_client_data client_data)
{
#ifdef HAVE_POLL
  struct pollfd fds;
#endif

  if (use_poll)
    {
#ifdef HAVE_POLL
      /* Check to see if poll () is usable. If not, we'll switch to
         use select. This can happen on systems like
         m68k-motorola-sys, `poll' cannot be used to wait for `stdin'.
         On m68k-motorola-sysv, tty's are not stream-based and not
         `poll'able. */
      fds.fd = fd;
      fds.events = POLLIN;
      if (poll (&fds, 1, 0) == 1 && (fds.revents & POLLNVAL))
	use_poll = 0;
#else
      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
    }
  if (use_poll)
    {
#ifdef HAVE_POLL
      create_file_handler (fd, POLLIN, proc, client_data);
#else
      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif
    }
  else
    create_file_handler (fd, GDB_READABLE | GDB_EXCEPTION, proc, client_data);
}

/* Add a file handler/descriptor to the list of descriptors we are
   interested in.  
   FD is the file descriptor for the file/stream to be listened to.  
   For the poll case, MASK is a combination (OR) of
   POLLIN, POLLRDNORM, POLLRDBAND, POLLPRI, POLLOUT, POLLWRNORM,
   POLLWRBAND: these are the events we are interested in. If any of them 
   occurs, proc should be called.
   For the select case, MASK is a combination of READABLE, WRITABLE, EXCEPTION.
   PROC is the procedure that will be called when an event occurs for
   FD.  CLIENT_DATA is the argument to pass to PROC. */
static void
create_file_handler (int fd, int mask, handler_func * proc, gdb_client_data client_data)
{
  file_handler *file_ptr;

  /* Do we already have a file handler for this file? (We may be
     changing its associated procedure). */
  for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
       file_ptr = file_ptr->next_file)
    {
      if (file_ptr->fd == fd)
	break;
    }

  /* It is a new file descriptor. Add it to the list. Otherwise, just
     change the data associated with it. */
  if (file_ptr == NULL)
    {
      file_ptr = (file_handler *) xmalloc (sizeof (file_handler));
      file_ptr->fd = fd;
      file_ptr->ready_mask = 0;
      file_ptr->next_file = gdb_notifier.first_file_handler;
      gdb_notifier.first_file_handler = file_ptr;
    }
  file_ptr->proc = proc;
  file_ptr->client_data = client_data;
  file_ptr->mask = mask;

  if (use_poll)
    {
#ifdef HAVE_POLL
      gdb_notifier.num_fds++;
      if (gdb_notifier.poll_fds)
	gdb_notifier.poll_fds =
	  (struct pollfd *) realloc (gdb_notifier.poll_fds,
			   (gdb_notifier.num_fds) * sizeof (struct pollfd));
      else
	gdb_notifier.poll_fds =
	  (struct pollfd *) xmalloc (sizeof (struct pollfd));
      (gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->fd = fd;
      (gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->events = mask;
      (gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->revents = 0;
#else
      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
    }
  else
    {
      if (mask & GDB_READABLE)
	FD_SET (fd, &gdb_notifier.check_masks[0]);
      else
	FD_CLR (fd, &gdb_notifier.check_masks[0]);

      if (mask & GDB_WRITABLE)
	FD_SET (fd, &gdb_notifier.check_masks[1]);
      else
	FD_CLR (fd, &gdb_notifier.check_masks[1]);

      if (mask & GDB_EXCEPTION)
	FD_SET (fd, &gdb_notifier.check_masks[2]);
      else
	FD_CLR (fd, &gdb_notifier.check_masks[2]);

      if (gdb_notifier.num_fds <= fd)
	gdb_notifier.num_fds = fd + 1;
    }
}

/* Remove the file descriptor FD from the list of monitored fd's: 
   i.e. we don't care anymore about events on the FD. */
void
delete_file_handler (int fd)
{
  file_handler *file_ptr, *prev_ptr = NULL;
  int i;
#ifdef HAVE_POLL
  int j;
  struct pollfd *new_poll_fds;
#endif

  /* Find the entry for the given file. */

  for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
       file_ptr = file_ptr->next_file)
    {
      if (file_ptr->fd == fd)
	break;
    }

  if (file_ptr == NULL)
    return;

  if (use_poll)
    {
#ifdef HAVE_POLL
      /* Create a new poll_fds array by copying every fd's information but the
         one we want to get rid of. */

      new_poll_fds =
	(struct pollfd *) xmalloc ((gdb_notifier.num_fds - 1) * sizeof (struct pollfd));

      for (i = 0, j = 0; i < gdb_notifier.num_fds; i++)
	{
	  if ((gdb_notifier.poll_fds + i)->fd != fd)
	    {
	      (new_poll_fds + j)->fd = (gdb_notifier.poll_fds + i)->fd;
	      (new_poll_fds + j)->events = (gdb_notifier.poll_fds + i)->events;
	      (new_poll_fds + j)->revents = (gdb_notifier.poll_fds + i)->revents;
	      j++;
	    }
	}
      free (gdb_notifier.poll_fds);
      gdb_notifier.poll_fds = new_poll_fds;
      gdb_notifier.num_fds--;
#else
      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
    }
  else
    {
      if (file_ptr->mask & GDB_READABLE)
	FD_CLR (fd, &gdb_notifier.check_masks[0]);
      if (file_ptr->mask & GDB_WRITABLE)
	FD_CLR (fd, &gdb_notifier.check_masks[1]);
      if (file_ptr->mask & GDB_EXCEPTION)
	FD_CLR (fd, &gdb_notifier.check_masks[2]);

      /* Find current max fd. */

      if ((fd + 1) == gdb_notifier.num_fds)
	{
	  gdb_notifier.num_fds--;
	  for (i = gdb_notifier.num_fds; i; i--)
	    {
	      if (FD_ISSET (i - 1, &gdb_notifier.check_masks[0])
		  || FD_ISSET (i - 1, &gdb_notifier.check_masks[1])
		  || FD_ISSET (i - 1, &gdb_notifier.check_masks[2]))
		break;
	    }
	  gdb_notifier.num_fds = i;
	}
    }

  /* Deactivate the file descriptor, by clearing its mask, 
     so that it will not fire again. */

  file_ptr->mask = 0;

  /* Get rid of the file handler in the file handler list. */
  if (file_ptr == gdb_notifier.first_file_handler)
    gdb_notifier.first_file_handler = file_ptr->next_file;
  else
    {
      for (prev_ptr = gdb_notifier.first_file_handler;
	   prev_ptr->next_file != file_ptr;
	   prev_ptr = prev_ptr->next_file)
	;
      prev_ptr->next_file = file_ptr->next_file;
    }
  free ((char *) file_ptr);
}

/* Handle the given event by calling the procedure associated to the
   corresponding file handler.  Called by process_event indirectly,
   through event_ptr->proc.  EVENT_FILE_DESC is file descriptor of the
   event in the front of the event queue. */
static void
handle_file_event (int event_file_desc)
{
  file_handler *file_ptr;
  int mask;
#ifdef HAVE_POLL
  int error_mask;
  int error_mask_returned;
#endif

  /* Search the file handler list to find one that matches the fd in
     the event. */
  for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
       file_ptr = file_ptr->next_file)
    {
      if (file_ptr->fd == event_file_desc)
	{
	  /* With poll, the ready_mask could have any of three events
	     set to 1: POLLHUP, POLLERR, POLLNVAL. These events cannot
	     be used in the requested event mask (events), but they
	     can be returned in the return mask (revents). We need to
	     check for those event too, and add them to the mask which
	     will be passed to the handler. */

	  /* See if the desired events (mask) match the received
	     events (ready_mask). */

	  if (use_poll)
	    {
#ifdef HAVE_POLL
	      error_mask = POLLHUP | POLLERR | POLLNVAL;
	      mask = (file_ptr->ready_mask & file_ptr->mask) |
		(file_ptr->ready_mask & error_mask);
	      error_mask_returned = mask & error_mask;

	      if (error_mask_returned != 0)
		{
		  /* Work in progress. We may need to tell somebody what
		     kind of error we had. */
		  if (error_mask_returned & POLLHUP)
		    printf_unfiltered ("Hangup detected on fd %d\n", file_ptr->fd);
		  if (error_mask_returned & POLLERR)
		    printf_unfiltered ("Error detected on fd %d\n", file_ptr->fd);
		  if (error_mask_returned & POLLNVAL)
		    printf_unfiltered ("Invalid or non-`poll'able fd %d\n", file_ptr->fd);
		  file_ptr->error = 1;
		}
	      else
		file_ptr->error = 0;
#else
	      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
	    }
	  else
	    {
	      if (file_ptr->ready_mask & GDB_EXCEPTION)
		{
		  printf_unfiltered ("Exception condition detected on fd %d\n", file_ptr->fd);
		  file_ptr->error = 1;
		}
	      else
		file_ptr->error = 0;
	      mask = file_ptr->ready_mask & file_ptr->mask;
	    }

	  /* Clear the received events for next time around. */
	  file_ptr->ready_mask = 0;

	  /* If there was a match, then call the handler. */
	  if (mask != 0)
	    (*file_ptr->proc) (file_ptr->error, file_ptr->client_data);
	  break;
	}
    }
}

/* Called by gdb_do_one_event to wait for new events on the 
   monitored file descriptors. Queue file events as they are 
   detected by the poll. 
   If there are no events, this function will block in the 
   call to poll.
   Return -1 if there are no files descriptors to monitor, 
   otherwise return 0. */
static int
gdb_wait_for_event (void)
{
  file_handler *file_ptr;
  gdb_event *file_event_ptr;
  int num_found = 0;
  int i;

  /* Make sure all output is done before getting another event. */
  gdb_flush (gdb_stdout);
  gdb_flush (gdb_stderr);

  if (gdb_notifier.num_fds == 0)
    return -1;

  if (use_poll)
    {
#ifdef HAVE_POLL
      num_found =
	poll (gdb_notifier.poll_fds,
	      (unsigned long) gdb_notifier.num_fds,
	      gdb_notifier.timeout_valid ? gdb_notifier.poll_timeout : -1);

      /* Don't print anything if we get out of poll because of a
         signal. */
      if (num_found == -1 && errno != EINTR)
	perror_with_name ("Poll");
#else
      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
    }
  else
    {
      gdb_notifier.ready_masks[0] = gdb_notifier.check_masks[0];
      gdb_notifier.ready_masks[1] = gdb_notifier.check_masks[1];
      gdb_notifier.ready_masks[2] = gdb_notifier.check_masks[2];
      num_found = select (gdb_notifier.num_fds,
			  &gdb_notifier.ready_masks[0],
			  &gdb_notifier.ready_masks[1],
			  &gdb_notifier.ready_masks[2],
			  gdb_notifier.timeout_valid
			  ? &gdb_notifier.select_timeout : NULL);

      /* Clear the masks after an error from select. */
      if (num_found == -1)
	{
	  FD_ZERO (&gdb_notifier.ready_masks[0]);
	  FD_ZERO (&gdb_notifier.ready_masks[1]);
	  FD_ZERO (&gdb_notifier.ready_masks[2]);
	  /* Dont print anything is we got a signal, let gdb handle it. */
	  if (errno != EINTR)
	    perror_with_name ("Select");
	}
    }

  /* Enqueue all detected file events. */

  if (use_poll)
    {
#ifdef HAVE_POLL
      for (i = 0; (i < gdb_notifier.num_fds) && (num_found > 0); i++)
	{
	  if ((gdb_notifier.poll_fds + i)->revents)
	    num_found--;
	  else
	    continue;

	  for (file_ptr = gdb_notifier.first_file_handler;
	       file_ptr != NULL;
	       file_ptr = file_ptr->next_file)
	    {
	      if (file_ptr->fd == (gdb_notifier.poll_fds + i)->fd)
		break;
	    }

	  if (file_ptr)
	    {
	      /* Enqueue an event only if this is still a new event for
	         this fd. */
	      if (file_ptr->ready_mask == 0)
		{
		  file_event_ptr = create_file_event (file_ptr->fd);
		  async_queue_event (file_event_ptr, TAIL);
		}
	    }

	  file_ptr->ready_mask = (gdb_notifier.poll_fds + i)->revents;
	}
#else
      internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
    }
  else
    {
      for (file_ptr = gdb_notifier.first_file_handler;
	   (file_ptr != NULL) && (num_found > 0);
	   file_ptr = file_ptr->next_file)
	{
	  int mask = 0;

	  if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[0]))
	    mask |= GDB_READABLE;
	  if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[1]))
	    mask |= GDB_WRITABLE;
	  if (FD_ISSET (file_ptr->fd, &gdb_notifier.ready_masks[2]))
	    mask |= GDB_EXCEPTION;

	  if (!mask)
	    continue;
	  else
	    num_found--;

	  /* Enqueue an event only if this is still a new event for
	     this fd. */

	  if (file_ptr->ready_mask == 0)
	    {
	      file_event_ptr = create_file_event (file_ptr->fd);
	      async_queue_event (file_event_ptr, TAIL);
	    }
	  file_ptr->ready_mask = mask;
	}
    }
  return 0;
}


/* Create an asynchronous handler, allocating memory for it. 
   Return a pointer to the newly created handler.
   This pointer will be used to invoke the handler by 
   invoke_async_signal_handler.
   PROC is the function to call with CLIENT_DATA argument 
   whenever the handler is invoked. */
async_signal_handler *
create_async_signal_handler (sig_handler_func * proc, gdb_client_data client_data)
{
  async_signal_handler *async_handler_ptr;

  async_handler_ptr =
    (async_signal_handler *) xmalloc (sizeof (async_signal_handler));
  async_handler_ptr->ready = 0;
  async_handler_ptr->next_handler = NULL;
  async_handler_ptr->proc = proc;
  async_handler_ptr->client_data = client_data;
  if (sighandler_list.first_handler == NULL)
    sighandler_list.first_handler = async_handler_ptr;
  else
    sighandler_list.last_handler->next_handler = async_handler_ptr;
  sighandler_list.last_handler = async_handler_ptr;
  return async_handler_ptr;
}

/* Mark the handler (ASYNC_HANDLER_PTR) as ready. This information will
   be used when the handlers are invoked, after we have waited for
   some event.  The caller of this function is the interrupt handler
   associated with a signal. */
void
mark_async_signal_handler (async_signal_handler * async_handler_ptr)
{
  ((async_signal_handler *) async_handler_ptr)->ready = 1;
  async_handler_ready = 1;
}

/* Call all the handlers that are ready. */
static void
invoke_async_signal_handler (void)
{
  async_signal_handler *async_handler_ptr;

  if (async_handler_ready == 0)
    return;
  async_handler_ready = 0;

  /* Invoke ready handlers. */

  while (1)
    {
      for (async_handler_ptr = sighandler_list.first_handler;
	   async_handler_ptr != NULL;
	   async_handler_ptr = async_handler_ptr->next_handler)
	{
	  if (async_handler_ptr->ready)
	    break;
	}
      if (async_handler_ptr == NULL)
	break;
      async_handler_ptr->ready = 0;
      (*async_handler_ptr->proc) (async_handler_ptr->client_data);
    }

  return;
}

/* Delete an asynchronous handler (ASYNC_HANDLER_PTR). 
   Free the space allocated for it.  */
void
delete_async_signal_handler (async_signal_handler ** async_handler_ptr)
{
  async_signal_handler *prev_ptr;

  if (sighandler_list.first_handler == (*async_handler_ptr))
    {
      sighandler_list.first_handler = (*async_handler_ptr)->next_handler;
      if (sighandler_list.first_handler == NULL)
	sighandler_list.last_handler = NULL;
    }
  else
    {
      prev_ptr = sighandler_list.first_handler;
      while (prev_ptr->next_handler != (*async_handler_ptr) && prev_ptr)
	prev_ptr = prev_ptr->next_handler;
      prev_ptr->next_handler = (*async_handler_ptr)->next_handler;
      if (sighandler_list.last_handler == (*async_handler_ptr))
	sighandler_list.last_handler = prev_ptr;
    }
  free ((char *) (*async_handler_ptr));
  (*async_handler_ptr) = NULL;
}

/* Is it necessary to call invoke_async_signal_handler? */
static int
check_async_ready (void)
{
  return async_handler_ready;
}

/* Create a timer that will expire in MILLISECONDS from now. When the
   timer is ready, PROC will be executed. At creation, the timer is
   aded to the timers queue.  This queue is kept sorted in order of
   increasing timers. Return a handle to the timer struct. */
int
create_timer (int milliseconds, timer_handler_func * proc, gdb_client_data client_data)
{
  struct gdb_timer *timer_ptr, *timer_index, *prev_timer;
  struct timeval time_now, delta;

  /* compute seconds */
  delta.tv_sec = milliseconds / 1000;
  /* compute microseconds */
  delta.tv_usec = (milliseconds % 1000) * 1000;

  gettimeofday (&time_now, NULL);

  timer_ptr = (struct gdb_timer *) xmalloc (sizeof (gdb_timer));
  timer_ptr->when.tv_sec = time_now.tv_sec + delta.tv_sec;
  timer_ptr->when.tv_usec = time_now.tv_usec + delta.tv_usec;
  /* carry? */
  if (timer_ptr->when.tv_usec >= 1000000)
    {
      timer_ptr->when.tv_sec += 1;
      timer_ptr->when.tv_usec -= 1000000;
    }
  timer_ptr->proc = proc;
  timer_ptr->client_data = client_data;
  timer_list.num_timers++;
  timer_ptr->timer_id = timer_list.num_timers;

  /* Now add the timer to the timer queue, making sure it is sorted in
     increasing order of expiration. */

  for (timer_index = timer_list.first_timer;
       timer_index != NULL;
       timer_index = timer_index->next)
    {
      /* If the seconds field is greater or if it is the same, but the
         microsecond field is greater. */
      if ((timer_index->when.tv_sec > timer_ptr->when.tv_sec) ||
	  ((timer_index->when.tv_sec == timer_ptr->when.tv_sec)
	   && (timer_index->when.tv_usec > timer_ptr->when.tv_usec)))
	break;
    }

  if (timer_index == timer_list.first_timer)
    {
      timer_ptr->next = timer_list.first_timer;
      timer_list.first_timer = timer_ptr;

    }
  else
    {
      for (prev_timer = timer_list.first_timer;
	   prev_timer->next != timer_index;
	   prev_timer = prev_timer->next)
	;

      prev_timer->next = timer_ptr;
      timer_ptr->next = timer_index;
    }

  gdb_notifier.timeout_valid = 0;
  return timer_ptr->timer_id;
}

/* There is a chance that the creator of the timer wants to get rid of
   it before it expires. */
void
delete_timer (int id)
{
  struct gdb_timer *timer_ptr, *prev_timer = NULL;

  /* Find the entry for the given timer. */

  for (timer_ptr = timer_list.first_timer; timer_ptr != NULL;
       timer_ptr = timer_ptr->next)
    {
      if (timer_ptr->timer_id == id)
	break;
    }

  if (timer_ptr == NULL)
    return;
  /* Get rid of the timer in the timer list. */
  if (timer_ptr == timer_list.first_timer)
    timer_list.first_timer = timer_ptr->next;
  else
    {
      for (prev_timer = timer_list.first_timer;
	   prev_timer->next != timer_ptr;
	   prev_timer = prev_timer->next)
	;
      prev_timer->next = timer_ptr->next;
    }
  free ((char *) timer_ptr);

  gdb_notifier.timeout_valid = 0;
}

/* When a timer event is put on the event queue, it will be handled by
   this function.  Just call the assiciated procedure and delete the
   timer event from the event queue. Repeat this for each timer that
   has expired. */
static void
handle_timer_event (int dummy)
{
  struct timeval time_now;
  struct gdb_timer *timer_ptr, *saved_timer;

  gettimeofday (&time_now, NULL);
  timer_ptr = timer_list.first_timer;

  while (timer_ptr != NULL)
    {
      if ((timer_ptr->when.tv_sec > time_now.tv_sec) ||
	  ((timer_ptr->when.tv_sec == time_now.tv_sec) &&
	   (timer_ptr->when.tv_usec > time_now.tv_usec)))
	break;

      /* Get rid of the timer from the beginning of the list. */
      timer_list.first_timer = timer_ptr->next;
      saved_timer = timer_ptr;
      timer_ptr = timer_ptr->next;
      /* Call the procedure associated with that timer. */
      (*saved_timer->proc) (saved_timer->client_data);
      free (saved_timer);
    }

  gdb_notifier.timeout_valid = 0;
}

/* Check whether any timers in the timers queue are ready. If at least
   one timer is ready, stick an event onto the event queue.  Even in
   case more than one timer is ready, one event is enough, because the
   handle_timer_event() will go through the timers list and call the
   procedures associated with all that have expired. Update the
   timeout for the select() or poll() as well. */
static void
poll_timers (void)
{
  struct timeval time_now, delta;
  gdb_event *event_ptr;

  if (timer_list.first_timer != NULL)
    {
      gettimeofday (&time_now, NULL);
      delta.tv_sec = timer_list.first_timer->when.tv_sec - time_now.tv_sec;
      delta.tv_usec = timer_list.first_timer->when.tv_usec - time_now.tv_usec;
      /* borrow? */
      if (delta.tv_usec < 0)
	{
	  delta.tv_sec -= 1;
	  delta.tv_usec += 1000000;
	}

      /* Oops it expired already. Tell select / poll to return
         immediately. (Cannot simply test if delta.tv_sec is negative
         because time_t might be unsigned.)  */
      if (timer_list.first_timer->when.tv_sec < time_now.tv_sec
	  || (timer_list.first_timer->when.tv_sec == time_now.tv_sec
	      && timer_list.first_timer->when.tv_usec < time_now.tv_usec))
	{
	  delta.tv_sec = 0;
	  delta.tv_usec = 0;
	}

      if (delta.tv_sec == 0 && delta.tv_usec == 0)
	{
	  event_ptr = (gdb_event *) xmalloc (sizeof (gdb_event));
	  event_ptr->proc = handle_timer_event;
	  event_ptr->fd = timer_list.first_timer->timer_id;
	  async_queue_event (event_ptr, TAIL);
	}

      /* Now we need to update the timeout for select/ poll, because we
         don't want to sit there while this timer is expiring. */
      if (use_poll)
	{
#ifdef HAVE_POLL
	  gdb_notifier.poll_timeout = delta.tv_sec * 1000;
#else
	  internal_error ("event-loop.c : use_poll without HAVE_POLL");
#endif /* HAVE_POLL */
	}
      else
	{
	  gdb_notifier.select_timeout.tv_sec = delta.tv_sec;
	  gdb_notifier.select_timeout.tv_usec = delta.tv_usec;
	}
      gdb_notifier.timeout_valid = 1;
    }
  else
    gdb_notifier.timeout_valid = 0;
}