/* Event loop machinery for GDB, the GNU debugger. Copyright 1999 Free Software Foundation, Inc. Written by Elena Zannoni 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" #ifdef HAVE_POLL #include #else #include #endif #include #include /* 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. */ #ifdef HAVE_POLL /* Poll based implementation of the notifier. */ static struct { /* Ptr to head of file handler list. */ file_handler *first_file_handler; /* Ptr to array of pollfd structures. */ struct pollfd *poll_fds; /* Number of file descriptors to monitor. */ int num_fds; } gdb_notifier; #else /* ! HAVE_POLL */ /* Select based implementation of the notifier. */ static struct { /* Ptr to head of file handler list. */ file_handler *first_file_handler; /* Masks to be used in the next call to select. Bits are set in response to calls to create_file_handler. */ fd_mask check_masks[3 * MASK_SIZE]; /* What file descriptors were found ready by select. */ fd_mask ready_masks[3 * MASK_SIZE]; /* Number of valid bits (highest fd value + 1). */ int num_fds; } gdb_notifier; #endif /* HAVE_POLL */ /* 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; /* Is 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 PARAMS ((int, int, handler_func *, gdb_client_data)); static void invoke_async_signal_handler PARAMS ((void)); static int gdb_wait_for_event PARAMS ((void)); static int gdb_do_one_event PARAMS ((void)); static int check_async_ready PARAMS ((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 (event_ptr, position) 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; } } /* 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 () { 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 associted 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 1 if something was done otherwise returns 0 (this can happen if there are no event sources to wait for). */ static int gdb_do_one_event () { int result = 0; while (1) { if (!SET_TOP_LEVEL ()) { /* Any events already waiting in the queue? */ if (process_event ()) { result = 1; break; } /* 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. */ result = gdb_wait_for_event (); if (result < 0) { result = 0; break; } /* Handle any new events occurred while waiting. */ if (process_event ()) { result = 1; break; } /* If gdb_wait_for_event has returned 1, it means that one event has been handled. We break out of the loop. */ if (result) break; } /* end of if !set_top_level */ else { /* 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. */ } } return result; } /* Start up the event loop. This is the entry point to the event loop from the command loop. */ void start_event_loop () { /* Loop until there is something to do. This is the entry point to the event loop engine. gdb_do_one_event will process one event for each invocation. It always returns 1, unless there are no more event sources registered. In this case it returns 0. */ while (gdb_do_one_event () != 0) ; /* 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 (fd, proc, client_data) int fd; void (*proc) (void); gdb_client_data client_data; { #ifdef HAVE_POLL create_file_handler (fd, POLLIN, (handler_func *) proc, client_data); #else create_file_handler (fd, GDB_READABLE, (handler_func *) proc, client_data); #endif } /* 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 (fd, mask, proc, client_data) int fd; int mask; handler_func *proc; gdb_client_data client_data; { file_handler *file_ptr; #ifndef HAVE_POLL int index, bit; #endif /* 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. */ 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; #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 /* ! HAVE_POLL */ index = fd / (NBBY * sizeof (fd_mask)); bit = 1 << (fd % (NBBY * sizeof (fd_mask))); if (mask & GDB_READABLE) gdb_notifier.check_masks[index] |= bit; else gdb_notifier.check_masks[index] &= ~bit; if (mask & GDB_WRITABLE) (gdb_notifier.check_masks + MASK_SIZE)[index] |= bit; else (gdb_notifier.check_masks + MASK_SIZE)[index] &= ~bit; if (mask & GDB_EXCEPTION) (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index] |= bit; else (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index] &= ~bit; if (gdb_notifier.num_fds <= fd) gdb_notifier.num_fds = fd + 1; #endif /* HAVE_POLL */ } /* 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 (fd) int fd; { file_handler *file_ptr, *prev_ptr = NULL; int i, j; struct pollfd *new_poll_fds; #ifndef HAVE_POLL int index, bit; unsigned long flags; #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; /* Deactivate the file descriptor, by clearing its mask, so that it will not fire again. */ file_ptr->mask = 0; #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 /* ! HAVE_POLL */ index = fd / (NBBY * sizeof (fd_mask)); bit = 1 << (fd % (NBBY * sizeof (fd_mask))); if (file_ptr->mask & GDB_READABLE) gdb_notifier.check_masks[index] &= ~bit; if (file_ptr->mask & GDB_WRITABLE) (gdb_notifier.check_masks + MASK_SIZE)[index] &= ~bit; if (file_ptr->mask & GDB_EXCEPTION) (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index] &= ~bit; /* Find current max fd. */ if ((fd + 1) == gdb_notifier.num_fds) { for (gdb_notifier.num_fds = 0; index >= 0; index--) { flags = gdb_notifier.check_masks[index] | (gdb_notifier.check_masks + MASK_SIZE)[index] | (gdb_notifier.check_masks + 2 * (MASK_SIZE))[index]; if (flags) { for (i = (NBBY * sizeof (fd_mask)); i > 0; i--) { if (flags & (((unsigned long) 1) << (i - 1))) break; } gdb_notifier.num_fds = index * (NBBY * sizeof (fd_mask)) + i; break; } } } #endif /* HAVE_POLL */ /* 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 (event_file_desc) int event_file_desc; { file_handler *file_ptr; int mask, error_mask; /* 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). */ #ifdef HAVE_POLL error_mask = POLLHUP | POLLERR | POLLNVAL; mask = (file_ptr->ready_mask & file_ptr->mask) | (file_ptr->ready_mask & error_mask); #else /* ! HAVE_POLL */ mask = file_ptr->ready_mask & file_ptr->mask; #endif /* HAVE_POLL */ /* 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->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 () { file_handler *file_ptr; gdb_event *file_event_ptr; int num_found = 0; int i; #ifndef HAVE_POLL int mask, bit, index; #endif /* 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; #ifdef HAVE_POLL num_found = poll (gdb_notifier.poll_fds, (unsigned long) gdb_notifier.num_fds, -1); #else /* ! HAVE_POLL */ memcpy (gdb_notifier.ready_masks, gdb_notifier.check_masks, 3 * MASK_SIZE * sizeof (fd_mask)); num_found = select (gdb_notifier.num_fds, (SELECT_MASK *) & gdb_notifier.ready_masks[0], (SELECT_MASK *) & gdb_notifier.ready_masks[MASK_SIZE], (SELECT_MASK *) & gdb_notifier.ready_masks[2 * MASK_SIZE], NULL); /* Clear the masks after an error from select. */ if (num_found == -1) memset (gdb_notifier.ready_masks, 0, 3 * MASK_SIZE * sizeof (fd_mask)); #endif /* HAVE_POLL */ /* Enqueue all detected file events. */ #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 = (gdb_event *) xmalloc (sizeof (gdb_event)); file_event_ptr->proc = handle_file_event; file_event_ptr->fd = file_ptr->fd; async_queue_event (file_event_ptr, TAIL); } } file_ptr->ready_mask = (gdb_notifier.poll_fds + i)->revents; } #else /* ! HAVE_POLL */ for (file_ptr = gdb_notifier.first_file_handler; (file_ptr != NULL) && (num_found > 0); file_ptr = file_ptr->next_file) { index = file_ptr->fd / (NBBY * sizeof (fd_mask)); bit = 1 << (file_ptr->fd % (NBBY * sizeof (fd_mask))); mask = 0; if (gdb_notifier.ready_masks[index] & bit) mask |= GDB_READABLE; if ((gdb_notifier.ready_masks + MASK_SIZE)[index] & bit) mask |= GDB_WRITABLE; if ((gdb_notifier.ready_masks + 2 * (MASK_SIZE))[index] & bit) 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 = (gdb_event *) xmalloc (sizeof (gdb_event)); file_event_ptr->proc = handle_file_event; file_event_ptr->fd = file_ptr->fd; async_queue_event (file_event_ptr, TAIL); } file_ptr->ready_mask = mask; } #endif /* HAVE_POLL */ 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 (proc, client_data) 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_handler_ptr) 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 () { 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_handler_ptr) 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 () { return async_handler_ready; }