1 /* Event loop machinery for GDB, the GNU debugger.
2 Copyright 1999 Free Software Foundation, Inc.
3 Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
23 #include "event-loop.h"
27 #include <sys/types.h>
33 - the first event in the queue is the head of the queue.
34 It will be the next to be serviced.
35 - the last event in the queue
37 Events can be inserted at the front of the queue or at the end of
38 the queue. Events will be extracted from the queue for processing
39 starting from the head. Therefore, events inserted at the head of
40 the queue will be processed in a last in first out fashoin, while
41 those inserted at the tail of the queue will be processed in a first
42 in first out manner. All the fields are NULL if the queue is
47 gdb_event
*first_event
; /* First pending event */
48 gdb_event
*last_event
; /* Last pending event */
52 /* Gdb_notifier is just a list of file descriptors gdb is interested in.
53 These are the input file descriptor, and the target file
54 descriptor. We have two flavors of the notifier, one for platforms
55 that have the POLL function, the other for those that don't, and
56 only support SELECT. Each of the elements in the gdb_notifier list is
57 basically a description of what kind of events gdb is interested
60 /* As of 1999-04-30 only the input file descriptor is registered with the
64 /* Poll based implementation of the notifier. */
68 /* Ptr to head of file handler list. */
69 file_handler
*first_file_handler
;
71 /* Ptr to array of pollfd structures. */
72 struct pollfd
*poll_fds
;
74 /* Number of file descriptors to monitor. */
80 #else /* ! HAVE_POLL */
82 /* Select based implementation of the notifier. */
86 /* Ptr to head of file handler list. */
87 file_handler
*first_file_handler
;
89 /* Masks to be used in the next call to select.
90 Bits are set in response to calls to create_file_handler. */
91 fd_mask check_masks
[3 * MASK_SIZE
];
93 /* What file descriptors were found ready by select. */
94 fd_mask ready_masks
[3 * MASK_SIZE
];
96 /* Number of valid bits (highest fd value + 1). */
102 #endif /* HAVE_POLL */
104 /* All the async_signal_handlers gdb is interested in are kept onto
108 /* Pointer to first in handler list. */
109 async_signal_handler
*first_handler
;
111 /* Pointer to last in handler list. */
112 async_signal_handler
*last_handler
;
116 /* Is any of the handlers ready? Check this variable using
117 check_async_ready. This is used by process_event, to determine
118 whether or not to invoke the invoke_async_signal_handler
120 static int async_handler_ready
= 0;
122 static void create_file_handler
PARAMS ((int, int, file_handler_func
*, gdb_client_data
));
123 static void invoke_async_signal_handler
PARAMS ((void));
124 static int gdb_wait_for_event
PARAMS ((void));
125 static int gdb_do_one_event
PARAMS ((void));
126 static int check_async_ready
PARAMS ((void));
129 /* Insert an event object into the gdb event queue at
130 the specified position.
131 POSITION can be head or tail, with values TAIL, HEAD.
132 EVENT_PTR points to the event to be inserted into the queue.
133 The caller must allocate memory for the event. It is freed
134 after the event has ben handled.
135 Events in the queue will be processed head to tail, therefore,
136 events inserted at the head of the queue will be processed
137 as last in first out. Event appended at the tail of the queue
138 will be processed first in first out. */
140 async_queue_event (event_ptr
, position
)
141 gdb_event
*event_ptr
;
142 queue_position position
;
144 if (position
== TAIL
)
146 /* The event will become the new last_event. */
148 event_ptr
->next_event
= NULL
;
149 if (event_queue
.first_event
== NULL
)
150 event_queue
.first_event
= event_ptr
;
152 event_queue
.last_event
->next_event
= event_ptr
;
153 event_queue
.last_event
= event_ptr
;
155 else if (position
== HEAD
)
157 /* The event becomes the new first_event. */
159 event_ptr
->next_event
= event_queue
.first_event
;
160 if (event_queue
.first_event
== NULL
)
161 event_queue
.last_event
= event_ptr
;
162 event_queue
.first_event
= event_ptr
;
166 /* Process one event.
167 The event can be the next one to be serviced in the event queue,
168 or an asynchronous event handler can be invoked in response to
169 the reception of a signal.
170 If an event was processed (either way), 1 is returned otherwise
172 Scan the queue from head to tail, processing therefore the high
173 priority events first, by invoking the associated event handler
178 gdb_event
*event_ptr
, *prev_ptr
;
179 event_handler_func
*proc
;
182 /* First let's see if there are any asynchronous event handlers that
183 are ready. These would be the result of invoking any of the
186 if (check_async_ready ())
188 invoke_async_signal_handler ();
192 /* Look in the event queue to find an event that is ready
195 for (event_ptr
= event_queue
.first_event
; event_ptr
!= NULL
;
196 event_ptr
= event_ptr
->next_event
)
198 /* Call the handler for the event. */
200 proc
= event_ptr
->proc
;
203 /* Let's get rid of the event from the event queue. We need to
204 do this now because while processing the event, the proc
205 function could end up calling 'error' and therefore jump out
206 to the caller of this function, gdb_do_one_event. In that
207 case, we would have on the event queue an event wich has been
208 processed, but not deleted. */
210 if (event_queue
.first_event
== event_ptr
)
212 event_queue
.first_event
= event_ptr
->next_event
;
213 if (event_ptr
->next_event
== NULL
)
214 event_queue
.last_event
= NULL
;
218 prev_ptr
= event_queue
.first_event
;
219 while (prev_ptr
->next_event
!= event_ptr
)
220 prev_ptr
= prev_ptr
->next_event
;
222 prev_ptr
->next_event
= event_ptr
->next_event
;
223 if (event_ptr
->next_event
== NULL
)
224 event_queue
.last_event
= prev_ptr
;
226 free ((char *) event_ptr
);
228 /* Now call the procedure associted with the event. */
233 /* this is the case if there are no event on the event queue. */
237 /* Process one high level event. If nothing is ready at this time,
238 wait for something to happen (via gdb_wait_for_event), then process
239 it. Returns 1 if something was done otherwise returns 0 (this can
240 happen if there are no event sources to wait for). */
248 if (!SET_TOP_LEVEL ())
250 /* Any events already waiting in the queue? */
251 if (process_event ())
257 /* Wait for a new event. If gdb_wait_for_event returns -1,
258 we should get out because this means that there are no
259 event sources left. This will make the event loop stop,
260 and the application exit. */
262 result
= gdb_wait_for_event ();
269 /* Handle any new events occurred while waiting. */
270 if (process_event ())
276 /* If gdb_wait_for_event has returned 1, it means that one
277 event has been handled. We break out of the loop. */
280 } /* end of if !set_top_level */
283 /* FIXME: this should really be a call to a hook that is
284 interface specific, because interfaces can display the
285 prompt in their own way. */
286 display_gdb_prompt (0);
287 /* Maybe better to set a flag to be checked somewhere as to
288 whether display the prompt or not. */
294 /* Start up the event loop. This is the entry point to the event loop
295 from the command loop. */
299 /* Loop until there is something to do. This is the entry point to
300 the event loop engine. gdb_do_one_event will process one event
301 for each invocation. It always returns 1, unless there are no
302 more event sources registered. In this case it returns 0. */
303 while (gdb_do_one_event () != 0)
306 /* We are done with the event loop. There are no more event sources
307 to listen to. So we exit GDB. */
313 /* Wrapper function for create_file_handler, so that the caller
314 doesn't have to know implementation details about the use of poll
317 add_file_handler (fd
, proc
, client_data
)
319 file_handler_func
*proc
;
320 gdb_client_data client_data
;
323 create_file_handler (fd
, POLLIN
, (file_handler_func
*) proc
, client_data
);
325 create_file_handler (fd
, GDB_READABLE
, (file_handler_func
*) proc
, client_data
);
329 /* Add a file handler/descriptor to the list of descriptors we are
331 FD is the file descriptor for the file/stream to be listened to.
332 For the poll case, MASK is a combination (OR) of
333 POLLIN, POLLRDNORM, POLLRDBAND, POLLPRI, POLLOUT, POLLWRNORM,
334 POLLWRBAND: these are the events we are interested in. If any of them
335 occurs, proc should be called.
336 For the select case, MASK is a combination of READABLE, WRITABLE, EXCEPTION.
337 PROC is the procedure that will be called when an event occurs for
338 FD. CLIENT_DATA is the argument to pass to PROC. */
340 create_file_handler (fd
, mask
, proc
, client_data
)
343 file_handler_func
*proc
;
344 gdb_client_data client_data
;
346 file_handler
*file_ptr
;
352 /* Do we already have a file handler for this file? (We may be
353 changing its associated procedure). */
354 for (file_ptr
= gdb_notifier
.first_file_handler
; file_ptr
!= NULL
;
355 file_ptr
= file_ptr
->next_file
)
357 if (file_ptr
->fd
== fd
)
361 /* It is a new file descriptor. */
362 if (file_ptr
== NULL
)
364 file_ptr
= (file_handler
*) xmalloc (sizeof (file_handler
));
366 file_ptr
->ready_mask
= 0;
367 file_ptr
->next_file
= gdb_notifier
.first_file_handler
;
368 gdb_notifier
.first_file_handler
= file_ptr
;
370 file_ptr
->proc
= proc
;
371 file_ptr
->client_data
= client_data
;
372 file_ptr
->mask
= mask
;
376 gdb_notifier
.num_fds
++;
377 if (gdb_notifier
.poll_fds
)
378 gdb_notifier
.poll_fds
=
379 (struct pollfd
*) realloc (gdb_notifier
.poll_fds
,
380 (gdb_notifier
.num_fds
) * sizeof (struct pollfd
));
382 gdb_notifier
.poll_fds
=
383 (struct pollfd
*) xmalloc (sizeof (struct pollfd
));
384 (gdb_notifier
.poll_fds
+ gdb_notifier
.num_fds
- 1)->fd
= fd
;
385 (gdb_notifier
.poll_fds
+ gdb_notifier
.num_fds
- 1)->events
= mask
;
386 (gdb_notifier
.poll_fds
+ gdb_notifier
.num_fds
- 1)->revents
= 0;
388 #else /* ! HAVE_POLL */
390 index
= fd
/ (NBBY
* sizeof (fd_mask
));
391 bit
= 1 << (fd
% (NBBY
* sizeof (fd_mask
)));
393 if (mask
& GDB_READABLE
)
394 gdb_notifier
.check_masks
[index
] |= bit
;
396 gdb_notifier
.check_masks
[index
] &= ~bit
;
398 if (mask
& GDB_WRITABLE
)
399 (gdb_notifier
.check_masks
+ MASK_SIZE
)[index
] |= bit
;
401 (gdb_notifier
.check_masks
+ MASK_SIZE
)[index
] &= ~bit
;
403 if (mask
& GDB_EXCEPTION
)
404 (gdb_notifier
.check_masks
+ 2 * (MASK_SIZE
))[index
] |= bit
;
406 (gdb_notifier
.check_masks
+ 2 * (MASK_SIZE
))[index
] &= ~bit
;
408 if (gdb_notifier
.num_fds
<= fd
)
409 gdb_notifier
.num_fds
= fd
+ 1;
411 #endif /* HAVE_POLL */
414 /* Remove the file descriptor FD from the list of monitored fd's:
415 i.e. we don't care anymore about events on the FD. */
417 delete_file_handler (fd
)
420 file_handler
*file_ptr
, *prev_ptr
= NULL
;
422 struct pollfd
*new_poll_fds
;
428 /* Find the entry for the given file. */
430 for (file_ptr
= gdb_notifier
.first_file_handler
; file_ptr
!= NULL
;
431 file_ptr
= file_ptr
->next_file
)
433 if (file_ptr
->fd
== fd
)
437 if (file_ptr
== NULL
)
440 /* Deactivate the file descriptor, by clearing its mask,
441 so that it will not fire again. */
446 /* Create a new poll_fds array by copying every fd's information but the
447 one we want to get rid of. */
450 (struct pollfd
*) xmalloc ((gdb_notifier
.num_fds
- 1) * sizeof (struct pollfd
));
452 for (i
= 0, j
= 0; i
< gdb_notifier
.num_fds
; i
++)
454 if ((gdb_notifier
.poll_fds
+ i
)->fd
!= fd
)
456 (new_poll_fds
+ j
)->fd
= (gdb_notifier
.poll_fds
+ i
)->fd
;
457 (new_poll_fds
+ j
)->events
= (gdb_notifier
.poll_fds
+ i
)->events
;
458 (new_poll_fds
+ j
)->revents
= (gdb_notifier
.poll_fds
+ i
)->revents
;
462 free (gdb_notifier
.poll_fds
);
463 gdb_notifier
.poll_fds
= new_poll_fds
;
464 gdb_notifier
.num_fds
--;
466 #else /* ! HAVE_POLL */
468 index
= fd
/ (NBBY
* sizeof (fd_mask
));
469 bit
= 1 << (fd
% (NBBY
* sizeof (fd_mask
)));
471 if (file_ptr
->mask
& GDB_READABLE
)
472 gdb_notifier
.check_masks
[index
] &= ~bit
;
473 if (file_ptr
->mask
& GDB_WRITABLE
)
474 (gdb_notifier
.check_masks
+ MASK_SIZE
)[index
] &= ~bit
;
475 if (file_ptr
->mask
& GDB_EXCEPTION
)
476 (gdb_notifier
.check_masks
+ 2 * (MASK_SIZE
))[index
] &= ~bit
;
478 /* Find current max fd. */
480 if ((fd
+ 1) == gdb_notifier
.num_fds
)
482 for (gdb_notifier
.num_fds
= 0; index
>= 0; index
--)
484 flags
= gdb_notifier
.check_masks
[index
]
485 | (gdb_notifier
.check_masks
+ MASK_SIZE
)[index
]
486 | (gdb_notifier
.check_masks
+ 2 * (MASK_SIZE
))[index
];
489 for (i
= (NBBY
* sizeof (fd_mask
)); i
> 0; i
--)
491 if (flags
& (((unsigned long) 1) << (i
- 1)))
494 gdb_notifier
.num_fds
= index
* (NBBY
* sizeof (fd_mask
)) + i
;
499 #endif /* HAVE_POLL */
501 /* Get rid of the file handler in the file handler list. */
502 if (file_ptr
== gdb_notifier
.first_file_handler
)
503 gdb_notifier
.first_file_handler
= file_ptr
->next_file
;
506 for (prev_ptr
= gdb_notifier
.first_file_handler
;
507 prev_ptr
->next_file
!= file_ptr
;
508 prev_ptr
= prev_ptr
->next_file
)
510 prev_ptr
->next_file
= file_ptr
->next_file
;
512 free ((char *) file_ptr
);
515 /* Handle the given event by calling the procedure associated to the
516 corresponding file handler. Called by process_event indirectly,
517 through event_ptr->proc. EVENT_FILE_DESC is file descriptor of the
518 event in the front of the event queue. */
520 handle_file_event (event_file_desc
)
523 file_handler
*file_ptr
;
524 int mask
, error_mask
;
526 /* Search the file handler list to find one that matches the fd in
528 for (file_ptr
= gdb_notifier
.first_file_handler
; file_ptr
!= NULL
;
529 file_ptr
= file_ptr
->next_file
)
531 if (file_ptr
->fd
== event_file_desc
)
533 /* With poll, the ready_mask could have any of three events
534 set to 1: POLLHUP, POLLERR, POLLNVAL. These events cannot
535 be used in the requested event mask (events), but they
536 can be returned in the return mask (revents). We need to
537 check for those event too, and add them to the mask which
538 will be passed to the handler. */
540 /* See if the desired events (mask) match the received
541 events (ready_mask). */
544 error_mask
= POLLHUP
| POLLERR
| POLLNVAL
;
545 mask
= (file_ptr
->ready_mask
& file_ptr
->mask
) |
546 (file_ptr
->ready_mask
& error_mask
);
548 #else /* ! HAVE_POLL */
549 mask
= file_ptr
->ready_mask
& file_ptr
->mask
;
550 #endif /* HAVE_POLL */
552 /* Clear the received events for next time around. */
553 file_ptr
->ready_mask
= 0;
555 /* If there was a match, then call the handler. */
557 (*file_ptr
->proc
) (file_ptr
->client_data
, mask
);
563 /* Called by gdb_do_one_event to wait for new events on the
564 monitored file descriptors. Queue file events as they are
565 detected by the poll.
566 If there are no events, this function will block in the
568 Return -1 if there are no files descriptors to monitor,
569 otherwise return 0. */
571 gdb_wait_for_event ()
573 file_handler
*file_ptr
;
574 gdb_event
*file_event_ptr
;
579 int mask
, bit
, index
;
582 if (gdb_notifier
.num_fds
== 0)
587 poll (gdb_notifier
.poll_fds
, (unsigned long) gdb_notifier
.num_fds
, -1);
589 #else /* ! HAVE_POLL */
590 memcpy (gdb_notifier
.ready_masks
,
591 gdb_notifier
.check_masks
,
592 3 * MASK_SIZE
* sizeof (fd_mask
));
593 num_found
= select (gdb_notifier
.num_fds
,
594 (SELECT_MASK
*) & gdb_notifier
.ready_masks
[0],
595 (SELECT_MASK
*) & gdb_notifier
.ready_masks
[MASK_SIZE
],
596 (SELECT_MASK
*) & gdb_notifier
.ready_masks
[2 * MASK_SIZE
],
599 /* Clear the masks after an error from select. */
601 memset (gdb_notifier
.ready_masks
,
602 0, 3 * MASK_SIZE
* sizeof (fd_mask
));
604 #endif /* HAVE_POLL */
606 /* Enqueue all detected file events. */
610 for (i
= 0; (i
< gdb_notifier
.num_fds
) && (num_found
> 0); i
++)
612 if ((gdb_notifier
.poll_fds
+ i
)->revents
)
617 for (file_ptr
= gdb_notifier
.first_file_handler
;
619 file_ptr
= file_ptr
->next_file
)
621 if (file_ptr
->fd
== (gdb_notifier
.poll_fds
+ i
)->fd
)
627 /* Enqueue an event only if this is still a new event for
629 if (file_ptr
->ready_mask
== 0)
632 (gdb_event
*) xmalloc (sizeof (gdb_event
));
633 file_event_ptr
->proc
= handle_file_event
;
634 file_event_ptr
->fd
= file_ptr
->fd
;
635 async_queue_event (file_event_ptr
, TAIL
);
639 file_ptr
->ready_mask
= (gdb_notifier
.poll_fds
+ i
)->revents
;
642 #else /* ! HAVE_POLL */
643 for (file_ptr
= gdb_notifier
.first_file_handler
;
644 (file_ptr
!= NULL
) && (num_found
> 0);
645 file_ptr
= file_ptr
->next_file
)
647 index
= file_ptr
->fd
/ (NBBY
* sizeof (fd_mask
));
648 bit
= 1 << (file_ptr
->fd
% (NBBY
* sizeof (fd_mask
)));
651 if (gdb_notifier
.ready_masks
[index
] & bit
)
652 mask
|= GDB_READABLE
;
653 if ((gdb_notifier
.ready_masks
+ MASK_SIZE
)[index
] & bit
)
654 mask
|= GDB_WRITABLE
;
655 if ((gdb_notifier
.ready_masks
+ 2 * (MASK_SIZE
))[index
] & bit
)
656 mask
|= GDB_EXCEPTION
;
663 /* Enqueue an event only if this is still a new event for
666 if (file_ptr
->ready_mask
== 0)
669 (gdb_event
*) xmalloc (sizeof (gdb_event
));
670 file_event_ptr
->proc
= handle_file_event
;
671 file_event_ptr
->fd
= file_ptr
->fd
;
672 async_queue_event (file_event_ptr
, TAIL
);
674 file_ptr
->ready_mask
= mask
;
676 #endif /* HAVE_POLL */
682 /* Create an asynchronous handler, allocating memory for it.
683 Return a pointer to the newly created handler.
684 This pointer will be used to invoke the handler by
685 invoke_async_signal_handler.
686 PROC is the function to call with CLIENT_DATA argument
687 whenever the handler is invoked. */
688 async_signal_handler
*
689 create_async_signal_handler (proc
, client_data
)
690 async_handler_func
*proc
;
691 gdb_client_data client_data
;
693 async_signal_handler
*async_handler_ptr
;
696 (async_signal_handler
*) xmalloc (sizeof (async_signal_handler
));
697 async_handler_ptr
->ready
= 0;
698 async_handler_ptr
->next_handler
= NULL
;
699 async_handler_ptr
->proc
= proc
;
700 async_handler_ptr
->client_data
= client_data
;
701 if (sighandler_list
.first_handler
== NULL
)
702 sighandler_list
.first_handler
= async_handler_ptr
;
704 sighandler_list
.last_handler
->next_handler
= async_handler_ptr
;
705 sighandler_list
.last_handler
= async_handler_ptr
;
706 return async_handler_ptr
;
709 /* Mark the handler (ASYNC_HANDLER_PTR) as ready. This information will
710 be used when the handlers are invoked, after we have waited for
711 some event. The caller of this function is the interrupt handler
712 associated with a signal. */
714 mark_async_signal_handler (async_handler_ptr
)
715 async_signal_handler
*async_handler_ptr
;
717 ((async_signal_handler
*) async_handler_ptr
)->ready
= 1;
718 async_handler_ready
= 1;
721 /* Call all the handlers that are ready. */
723 invoke_async_signal_handler ()
725 async_signal_handler
*async_handler_ptr
;
727 if (async_handler_ready
== 0)
729 async_handler_ready
= 0;
731 /* Invoke ready handlers. */
735 for (async_handler_ptr
= sighandler_list
.first_handler
;
736 async_handler_ptr
!= NULL
;
737 async_handler_ptr
= async_handler_ptr
->next_handler
)
739 if (async_handler_ptr
->ready
)
742 if (async_handler_ptr
== NULL
)
744 async_handler_ptr
->ready
= 0;
745 (*async_handler_ptr
->proc
) (async_handler_ptr
->client_data
);
751 /* Delete an asynchronous handler (ASYNC_HANDLER_PTR).
752 Free the space allocated for it. */
754 delete_async_signal_handler (async_handler_ptr
)
755 async_signal_handler
*async_handler_ptr
;
757 async_signal_handler
*prev_ptr
;
759 if (sighandler_list
.first_handler
== async_handler_ptr
)
761 sighandler_list
.first_handler
= async_handler_ptr
->next_handler
;
762 if (sighandler_list
.first_handler
== NULL
)
763 sighandler_list
.last_handler
= NULL
;
767 prev_ptr
= sighandler_list
.first_handler
;
768 while (prev_ptr
->next_handler
!= async_handler_ptr
)
769 prev_ptr
= prev_ptr
->next_handler
;
770 prev_ptr
->next_handler
= async_handler_ptr
->next_handler
;
771 if (sighandler_list
.last_handler
== async_handler_ptr
)
772 sighandler_list
.last_handler
= prev_ptr
;
774 free ((char *) async_handler_ptr
);
777 /* Is it necessary to call invoke_async_signal_handler? */
781 return async_handler_ready
;