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,
20 Boston, MA 02111-1307, USA. */
24 #include "event-loop.h"
28 #include <sys/types.h>
34 - the first event in the queue is the head of the queue.
35 It will be the next to be serviced.
36 - the last event in the queue
38 Events can be inserted at the front of the queue or at the end of
39 the queue. Events will be extracted from the queue for processing
40 starting from the head. Therefore, events inserted at the head of
41 the queue will be processed in a last in first out fashion, while
42 those inserted at the tail of the queue will be processed in a first
43 in first out manner. All the fields are NULL if the queue is
48 gdb_event *first_event; /* First pending event */
49 gdb_event *last_event; /* Last pending event */
53 /* Gdb_notifier is just a list of file descriptors gdb is interested in.
54 These are the input file descriptor, and the target file
55 descriptor. We have two flavors of the notifier, one for platforms
56 that have the POLL function, the other for those that don't, and
57 only support SELECT. Each of the elements in the gdb_notifier list is
58 basically a description of what kind of events gdb is interested
61 /* As of 1999-04-30 only the input file descriptor is registered with the
65 /* Poll based implementation of the notifier. */
69 /* Ptr to head of file handler list. */
70 file_handler *first_file_handler;
72 /* Ptr to array of pollfd structures. */
73 struct pollfd *poll_fds;
75 /* Number of file descriptors to monitor. */
81 #else /* ! HAVE_POLL */
83 /* Select based implementation of the notifier. */
87 /* Ptr to head of file handler list. */
88 file_handler *first_file_handler;
90 /* Masks to be used in the next call to select.
91 Bits are set in response to calls to create_file_handler. */
92 fd_mask check_masks[3 * MASK_SIZE];
94 /* What file descriptors were found ready by select. */
95 fd_mask ready_masks[3 * MASK_SIZE];
97 /* Number of valid bits (highest fd value + 1). */
103 #endif /* HAVE_POLL */
105 /* All the async_signal_handlers gdb is interested in are kept onto
109 /* Pointer to first in handler list. */
110 async_signal_handler *first_handler;
112 /* Pointer to last in handler list. */
113 async_signal_handler *last_handler;
117 /* Is any of the handlers ready? Check this variable using
118 check_async_ready. This is used by process_event, to determine
119 whether or not to invoke the invoke_async_signal_handler
121 static int async_handler_ready = 0;
123 static void create_file_handler PARAMS ((int, int, file_handler_func *, gdb_client_data));
124 static void invoke_async_signal_handler PARAMS ((void));
125 static int gdb_wait_for_event PARAMS ((void));
126 static int gdb_do_one_event PARAMS ((void));
127 static int check_async_ready PARAMS ((void));
130 /* Insert an event object into the gdb event queue at
131 the specified position.
132 POSITION can be head or tail, with values TAIL, HEAD.
133 EVENT_PTR points to the event to be inserted into the queue.
134 The caller must allocate memory for the event. It is freed
135 after the event has ben handled.
136 Events in the queue will be processed head to tail, therefore,
137 events inserted at the head of the queue will be processed
138 as last in first out. Event appended at the tail of the queue
139 will be processed first in first out. */
141 async_queue_event (event_ptr, position)
142 gdb_event *event_ptr;
143 queue_position position;
145 if (position == TAIL)
147 /* The event will become the new last_event. */
149 event_ptr->next_event = NULL;
150 if (event_queue.first_event == NULL)
151 event_queue.first_event = event_ptr;
153 event_queue.last_event->next_event = event_ptr;
154 event_queue.last_event = event_ptr;
156 else if (position == HEAD)
158 /* The event becomes the new first_event. */
160 event_ptr->next_event = event_queue.first_event;
161 if (event_queue.first_event == NULL)
162 event_queue.last_event = event_ptr;
163 event_queue.first_event = event_ptr;
167 /* Process one event.
168 The event can be the next one to be serviced in the event queue,
169 or an asynchronous event handler can be invoked in response to
170 the reception of a signal.
171 If an event was processed (either way), 1 is returned otherwise
173 Scan the queue from head to tail, processing therefore the high
174 priority events first, by invoking the associated event handler
179 gdb_event *event_ptr, *prev_ptr;
180 event_handler_func *proc;
183 /* First let's see if there are any asynchronous event handlers that
184 are ready. These would be the result of invoking any of the
187 if (check_async_ready ())
189 invoke_async_signal_handler ();
193 /* Look in the event queue to find an event that is ready
196 for (event_ptr = event_queue.first_event; event_ptr != NULL;
197 event_ptr = event_ptr->next_event)
199 /* Call the handler for the event. */
201 proc = event_ptr->proc;
204 /* Let's get rid of the event from the event queue. We need to
205 do this now because while processing the event, the proc
206 function could end up calling 'error' and therefore jump out
207 to the caller of this function, gdb_do_one_event. In that
208 case, we would have on the event queue an event wich has been
209 processed, but not deleted. */
211 if (event_queue.first_event == event_ptr)
213 event_queue.first_event = event_ptr->next_event;
214 if (event_ptr->next_event == NULL)
215 event_queue.last_event = NULL;
219 prev_ptr = event_queue.first_event;
220 while (prev_ptr->next_event != event_ptr)
221 prev_ptr = prev_ptr->next_event;
223 prev_ptr->next_event = event_ptr->next_event;
224 if (event_ptr->next_event == NULL)
225 event_queue.last_event = prev_ptr;
227 free ((char *) event_ptr);
229 /* Now call the procedure associted with the event. */
234 /* this is the case if there are no event on the event queue. */
238 /* Process one high level event. If nothing is ready at this time,
239 wait for something to happen (via gdb_wait_for_event), then process
240 it. Returns 1 if something was done otherwise returns 0 (this can
241 happen if there are no event sources to wait for). */
249 if (!SET_TOP_LEVEL ())
251 /* Any events already waiting in the queue? */
252 if (process_event ())
258 /* Wait for a new event. If gdb_wait_for_event returns -1,
259 we should get out because this means that there are no
260 event sources left. This will make the event loop stop,
261 and the application exit. */
263 result = gdb_wait_for_event ();
270 /* Handle any new events occurred while waiting. */
271 if (process_event ())
277 /* If gdb_wait_for_event has returned 1, it means that one
278 event has been handled. We break out of the loop. */
281 } /* end of if !set_top_level */
284 /* FIXME: this should really be a call to a hook that is
285 interface specific, because interfaces can display the
286 prompt in their own way. */
287 display_gdb_prompt (0);
288 /* Maybe better to set a flag to be checked somewhere as to
289 whether display the prompt or not. */
296 /* Start up the event loop. This is the entry point to the event loop
297 from the command loop. */
301 /* Loop until there is something to do. This is the entry point to
302 the event loop engine. gdb_do_one_event will process one event
303 for each invocation. It always returns 1, unless there are no
304 more event sources registered. In this case it returns 0. */
305 while (gdb_do_one_event () != 0)
308 /* We are done with the event loop. There are no more event sources
309 to listen to. So we exit GDB. */
315 /* Wrapper function for create_file_handler, so that the caller
316 doesn't have to know implementation details about the use of poll
319 add_file_handler (fd, proc, client_data)
321 file_handler_func *proc;
322 gdb_client_data client_data;
325 create_file_handler (fd, POLLIN, (file_handler_func *) proc, client_data);
327 create_file_handler (fd, GDB_READABLE, (file_handler_func *) proc, client_data);
331 /* Add a file handler/descriptor to the list of descriptors we are
333 FD is the file descriptor for the file/stream to be listened to.
334 For the poll case, MASK is a combination (OR) of
335 POLLIN, POLLRDNORM, POLLRDBAND, POLLPRI, POLLOUT, POLLWRNORM,
336 POLLWRBAND: these are the events we are interested in. If any of them
337 occurs, proc should be called.
338 For the select case, MASK is a combination of READABLE, WRITABLE, EXCEPTION.
339 PROC is the procedure that will be called when an event occurs for
340 FD. CLIENT_DATA is the argument to pass to PROC. */
342 create_file_handler (fd, mask, proc, client_data)
345 file_handler_func *proc;
346 gdb_client_data client_data;
348 file_handler *file_ptr;
354 /* Do we already have a file handler for this file? (We may be
355 changing its associated procedure). */
356 for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
357 file_ptr = file_ptr->next_file)
359 if (file_ptr->fd == fd)
363 /* It is a new file descriptor. */
364 if (file_ptr == NULL)
366 file_ptr = (file_handler *) xmalloc (sizeof (file_handler));
368 file_ptr->ready_mask = 0;
369 file_ptr->next_file = gdb_notifier.first_file_handler;
370 gdb_notifier.first_file_handler = file_ptr;
372 file_ptr->proc = proc;
373 file_ptr->client_data = client_data;
374 file_ptr->mask = mask;
378 gdb_notifier.num_fds++;
379 if (gdb_notifier.poll_fds)
380 gdb_notifier.poll_fds =
381 (struct pollfd *) realloc (gdb_notifier.poll_fds,
382 (gdb_notifier.num_fds) * sizeof (struct pollfd));
384 gdb_notifier.poll_fds =
385 (struct pollfd *) xmalloc (sizeof (struct pollfd));
386 (gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->fd = fd;
387 (gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->events = mask;
388 (gdb_notifier.poll_fds + gdb_notifier.num_fds - 1)->revents = 0;
390 #else /* ! HAVE_POLL */
392 index = fd / (NBBY * sizeof (fd_mask));
393 bit = 1 << (fd % (NBBY * sizeof (fd_mask)));
395 if (mask & GDB_READABLE)
396 gdb_notifier.check_masks[index] |= bit;
398 gdb_notifier.check_masks[index] &= ~bit;
400 if (mask & GDB_WRITABLE)
401 (gdb_notifier.check_masks + MASK_SIZE)[index] |= bit;
403 (gdb_notifier.check_masks + MASK_SIZE)[index] &= ~bit;
405 if (mask & GDB_EXCEPTION)
406 (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index] |= bit;
408 (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index] &= ~bit;
410 if (gdb_notifier.num_fds <= fd)
411 gdb_notifier.num_fds = fd + 1;
413 #endif /* HAVE_POLL */
416 /* Remove the file descriptor FD from the list of monitored fd's:
417 i.e. we don't care anymore about events on the FD. */
419 delete_file_handler (fd)
422 file_handler *file_ptr, *prev_ptr = NULL;
424 struct pollfd *new_poll_fds;
430 /* Find the entry for the given file. */
432 for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
433 file_ptr = file_ptr->next_file)
435 if (file_ptr->fd == fd)
439 if (file_ptr == NULL)
442 /* Deactivate the file descriptor, by clearing its mask,
443 so that it will not fire again. */
448 /* Create a new poll_fds array by copying every fd's information but the
449 one we want to get rid of. */
452 (struct pollfd *) xmalloc ((gdb_notifier.num_fds - 1) * sizeof (struct pollfd));
454 for (i = 0, j = 0; i < gdb_notifier.num_fds; i++)
456 if ((gdb_notifier.poll_fds + i)->fd != fd)
458 (new_poll_fds + j)->fd = (gdb_notifier.poll_fds + i)->fd;
459 (new_poll_fds + j)->events = (gdb_notifier.poll_fds + i)->events;
460 (new_poll_fds + j)->revents = (gdb_notifier.poll_fds + i)->revents;
464 free (gdb_notifier.poll_fds);
465 gdb_notifier.poll_fds = new_poll_fds;
466 gdb_notifier.num_fds--;
468 #else /* ! HAVE_POLL */
470 index = fd / (NBBY * sizeof (fd_mask));
471 bit = 1 << (fd % (NBBY * sizeof (fd_mask)));
473 if (file_ptr->mask & GDB_READABLE)
474 gdb_notifier.check_masks[index] &= ~bit;
475 if (file_ptr->mask & GDB_WRITABLE)
476 (gdb_notifier.check_masks + MASK_SIZE)[index] &= ~bit;
477 if (file_ptr->mask & GDB_EXCEPTION)
478 (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index] &= ~bit;
480 /* Find current max fd. */
482 if ((fd + 1) == gdb_notifier.num_fds)
484 for (gdb_notifier.num_fds = 0; index >= 0; index--)
486 flags = gdb_notifier.check_masks[index]
487 | (gdb_notifier.check_masks + MASK_SIZE)[index]
488 | (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index];
491 for (i = (NBBY * sizeof (fd_mask)); i > 0; i--)
493 if (flags & (((unsigned long) 1) << (i - 1)))
496 gdb_notifier.num_fds = index * (NBBY * sizeof (fd_mask)) + i;
501 #endif /* HAVE_POLL */
503 /* Get rid of the file handler in the file handler list. */
504 if (file_ptr == gdb_notifier.first_file_handler)
505 gdb_notifier.first_file_handler = file_ptr->next_file;
508 for (prev_ptr = gdb_notifier.first_file_handler;
509 prev_ptr->next_file != file_ptr;
510 prev_ptr = prev_ptr->next_file)
512 prev_ptr->next_file = file_ptr->next_file;
514 free ((char *) file_ptr);
517 /* Handle the given event by calling the procedure associated to the
518 corresponding file handler. Called by process_event indirectly,
519 through event_ptr->proc. EVENT_FILE_DESC is file descriptor of the
520 event in the front of the event queue. */
522 handle_file_event (event_file_desc)
525 file_handler *file_ptr;
526 int mask, error_mask;
528 /* Search the file handler list to find one that matches the fd in
530 for (file_ptr = gdb_notifier.first_file_handler; file_ptr != NULL;
531 file_ptr = file_ptr->next_file)
533 if (file_ptr->fd == event_file_desc)
535 /* With poll, the ready_mask could have any of three events
536 set to 1: POLLHUP, POLLERR, POLLNVAL. These events cannot
537 be used in the requested event mask (events), but they
538 can be returned in the return mask (revents). We need to
539 check for those event too, and add them to the mask which
540 will be passed to the handler. */
542 /* See if the desired events (mask) match the received
543 events (ready_mask). */
546 error_mask = POLLHUP | POLLERR | POLLNVAL;
547 mask = (file_ptr->ready_mask & file_ptr->mask) |
548 (file_ptr->ready_mask & error_mask);
550 #else /* ! HAVE_POLL */
551 mask = file_ptr->ready_mask & file_ptr->mask;
552 #endif /* HAVE_POLL */
554 /* Clear the received events for next time around. */
555 file_ptr->ready_mask = 0;
557 /* If there was a match, then call the handler. */
559 (*file_ptr->proc) (file_ptr->client_data, mask);
565 /* Called by gdb_do_one_event to wait for new events on the
566 monitored file descriptors. Queue file events as they are
567 detected by the poll.
568 If there are no events, this function will block in the
570 Return -1 if there are no files descriptors to monitor,
571 otherwise return 0. */
573 gdb_wait_for_event ()
575 file_handler *file_ptr;
576 gdb_event *file_event_ptr;
581 int mask, bit, index;
584 if (gdb_notifier.num_fds == 0)
589 poll (gdb_notifier.poll_fds, (unsigned long) gdb_notifier.num_fds, -1);
591 #else /* ! HAVE_POLL */
592 memcpy (gdb_notifier.ready_masks,
593 gdb_notifier.check_masks,
594 3 * MASK_SIZE * sizeof (fd_mask));
595 num_found = select (gdb_notifier.num_fds,
596 (SELECT_MASK *) & gdb_notifier.ready_masks[0],
597 (SELECT_MASK *) & gdb_notifier.ready_masks[MASK_SIZE],
598 (SELECT_MASK *) & gdb_notifier.ready_masks[2 * MASK_SIZE],
601 /* Clear the masks after an error from select. */
603 memset (gdb_notifier.ready_masks,
604 0, 3 * MASK_SIZE * sizeof (fd_mask));
606 #endif /* HAVE_POLL */
608 /* Enqueue all detected file events. */
612 for (i = 0; (i < gdb_notifier.num_fds) && (num_found > 0); i++)
614 if ((gdb_notifier.poll_fds + i)->revents)
619 for (file_ptr = gdb_notifier.first_file_handler;
621 file_ptr = file_ptr->next_file)
623 if (file_ptr->fd == (gdb_notifier.poll_fds + i)->fd)
629 /* Enqueue an event only if this is still a new event for
631 if (file_ptr->ready_mask == 0)
634 (gdb_event *) xmalloc (sizeof (gdb_event));
635 file_event_ptr->proc = handle_file_event;
636 file_event_ptr->fd = file_ptr->fd;
637 async_queue_event (file_event_ptr, TAIL);
641 file_ptr->ready_mask = (gdb_notifier.poll_fds + i)->revents;
644 #else /* ! HAVE_POLL */
645 for (file_ptr = gdb_notifier.first_file_handler;
646 (file_ptr != NULL) && (num_found > 0);
647 file_ptr = file_ptr->next_file)
649 index = file_ptr->fd / (NBBY * sizeof (fd_mask));
650 bit = 1 << (file_ptr->fd % (NBBY * sizeof (fd_mask)));
653 if (gdb_notifier.ready_masks[index] & bit)
654 mask |= GDB_READABLE;
655 if ((gdb_notifier.ready_masks + MASK_SIZE)[index] & bit)
656 mask |= GDB_WRITABLE;
657 if ((gdb_notifier.ready_masks + 2 * (MASK_SIZE))[index] & bit)
658 mask |= GDB_EXCEPTION;
665 /* Enqueue an event only if this is still a new event for
668 if (file_ptr->ready_mask == 0)
671 (gdb_event *) xmalloc (sizeof (gdb_event));
672 file_event_ptr->proc = handle_file_event;
673 file_event_ptr->fd = file_ptr->fd;
674 async_queue_event (file_event_ptr, TAIL);
676 file_ptr->ready_mask = mask;
678 #endif /* HAVE_POLL */
684 /* Create an asynchronous handler, allocating memory for it.
685 Return a pointer to the newly created handler.
686 This pointer will be used to invoke the handler by
687 invoke_async_signal_handler.
688 PROC is the function to call with CLIENT_DATA argument
689 whenever the handler is invoked. */
690 async_signal_handler *
691 create_async_signal_handler (proc, client_data)
692 async_handler_func *proc;
693 gdb_client_data client_data;
695 async_signal_handler *async_handler_ptr;
698 (async_signal_handler *) xmalloc (sizeof (async_signal_handler));
699 async_handler_ptr->ready = 0;
700 async_handler_ptr->next_handler = NULL;
701 async_handler_ptr->proc = proc;
702 async_handler_ptr->client_data = client_data;
703 if (sighandler_list.first_handler == NULL)
704 sighandler_list.first_handler = async_handler_ptr;
706 sighandler_list.last_handler->next_handler = async_handler_ptr;
707 sighandler_list.last_handler = async_handler_ptr;
708 return async_handler_ptr;
711 /* Mark the handler (ASYNC_HANDLER_PTR) as ready. This information will
712 be used when the handlers are invoked, after we have waited for
713 some event. The caller of this function is the interrupt handler
714 associated with a signal. */
716 mark_async_signal_handler (async_handler_ptr)
717 async_signal_handler *async_handler_ptr;
719 ((async_signal_handler *) async_handler_ptr)->ready = 1;
720 async_handler_ready = 1;
723 /* Call all the handlers that are ready. */
725 invoke_async_signal_handler ()
727 async_signal_handler *async_handler_ptr;
729 if (async_handler_ready == 0)
731 async_handler_ready = 0;
733 /* Invoke ready handlers. */
737 for (async_handler_ptr = sighandler_list.first_handler;
738 async_handler_ptr != NULL;
739 async_handler_ptr = async_handler_ptr->next_handler)
741 if (async_handler_ptr->ready)
744 if (async_handler_ptr == NULL)
746 async_handler_ptr->ready = 0;
747 (*async_handler_ptr->proc) (async_handler_ptr->client_data);
753 /* Delete an asynchronous handler (ASYNC_HANDLER_PTR).
754 Free the space allocated for it. */
756 delete_async_signal_handler (async_handler_ptr)
757 async_signal_handler **async_handler_ptr;
759 async_signal_handler *prev_ptr;
761 if (sighandler_list.first_handler == (*async_handler_ptr))
763 sighandler_list.first_handler = (*async_handler_ptr)->next_handler;
764 if (sighandler_list.first_handler == NULL)
765 sighandler_list.last_handler = NULL;
769 prev_ptr = sighandler_list.first_handler;
770 while (prev_ptr->next_handler != (*async_handler_ptr) && prev_ptr)
771 prev_ptr = prev_ptr->next_handler;
772 prev_ptr->next_handler = (*async_handler_ptr)->next_handler;
773 if (sighandler_list.last_handler == (*async_handler_ptr))
774 sighandler_list.last_handler = prev_ptr;
776 free ((char *) (*async_handler_ptr));
777 (*async_handler_ptr) = NULL;
780 /* Is it necessary to call invoke_async_signal_handler? */
784 return async_handler_ready;