1 /* Definitions used by the GDB event loop. 2 Copyright (C) 1999-2013 Free Software Foundation, Inc. 3 Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions. 4 5 This file is part of GDB. 6 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 3 of the License, or 10 (at your option) any later version. 11 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. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 /* An event loop listens for events from multiple event sources. When 21 an event arrives, it is queued and processed by calling the 22 appropriate event handler. The event loop then continues to listen 23 for more events. An event loop completes when there are no event 24 sources to listen on. External event sources can be plugged into 25 the loop. 26 27 There are 4 main components: 28 - a list of file descriptors to be monitored, GDB_NOTIFIER. 29 - a list of asynchronous event sources to be monitored, 30 ASYNC_EVENT_HANDLER_LIST. 31 - a list of events that have occurred, EVENT_QUEUE. 32 - a list of signal handling functions, SIGHANDLER_LIST. 33 34 GDB_NOTIFIER keeps track of the file descriptor based event 35 sources. ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous 36 event sources that are signalled by some component of gdb, usually 37 a target_ops instance. Event sources for gdb are currently the UI 38 and the target. Gdb communicates with the command line user 39 interface via the readline library and usually communicates with 40 remote targets via a serial port. Serial ports are represented in 41 GDB as file descriptors and select/poll calls. For native targets 42 instead, the communication varies across operating system debug 43 APIs, but usually consists of calls to ptrace and waits (via 44 signals) or calls to poll/select (via file descriptors). In the 45 current gdb, the code handling events related to the target resides 46 in wait_for_inferior for synchronous targets; or, for asynchronous 47 capable targets, by having the target register either a target 48 controlled file descriptor and/or an asynchronous event source in 49 the event loop, with the fetch_inferior_event function as the event 50 callback. In both the synchronous and asynchronous cases, usually 51 the target event is collected through the target_wait interface. 52 The target is free to install other event sources in the event loop 53 if it so requires. 54 55 EVENT_QUEUE keeps track of the events that have happened during the 56 last iteration of the event loop, and need to be processed. An 57 event is represented by a procedure to be invoked in order to 58 process the event. The queue is scanned head to tail. If the 59 event of interest is a change of state in a file descriptor, then a 60 call to poll or select will be made to detect it. 61 62 If the events generate signals, they are also queued by special 63 functions that are invoked through traditional signal handlers. 64 The actions to be taken is response to such events will be executed 65 when the SIGHANDLER_LIST is scanned, the next time through the 66 infinite loop. 67 68 Corollary tasks are the creation and deletion of event sources. */ 69 70 typedef void *gdb_client_data; 71 struct async_signal_handler; 72 struct async_event_handler; 73 typedef void (handler_func) (int, gdb_client_data); 74 typedef void (sig_handler_func) (gdb_client_data); 75 typedef void (async_event_handler_func) (gdb_client_data); 76 typedef void (timer_handler_func) (gdb_client_data); 77 78 /* Exported functions from event-loop.c */ 79 80 extern void initialize_event_loop (void); 81 extern void start_event_loop (void); 82 extern int gdb_do_one_event (void); 83 extern void delete_file_handler (int fd); 84 extern void add_file_handler (int fd, handler_func *proc, 85 gdb_client_data client_data); 86 extern struct async_signal_handler * 87 create_async_signal_handler (sig_handler_func *proc, 88 gdb_client_data client_data); 89 extern void delete_async_signal_handler (struct async_signal_handler **); 90 extern int create_timer (int milliseconds, 91 timer_handler_func *proc, 92 gdb_client_data client_data); 93 extern void delete_timer (int id); 94 95 /* Call the handler from HANDLER immediately. This function 96 runs signal handlers when returning to the event loop would be too 97 slow. Do not call this directly; use gdb_call_async_signal_handler, 98 below, with IMMEDIATE_P == 1. */ 99 void call_async_signal_handler (struct async_signal_handler *handler); 100 101 /* Call the handler from HANDLER the next time through the event loop. 102 Do not call this directly; use gdb_call_async_signal_handler, 103 below, with IMMEDIATE_P == 0. */ 104 void mark_async_signal_handler (struct async_signal_handler *handler); 105 106 /* Wrapper for the body of signal handlers. Call this function from 107 any SIGINT handler which needs to access GDB data structures or 108 escape via longjmp. If IMMEDIATE_P is set, this triggers either 109 immediately (for POSIX platforms), or from gdb_select (for 110 MinGW). If IMMEDIATE_P is clear, the handler will run the next 111 time we return to the event loop and any current select calls 112 will be interrupted. */ 113 114 void gdb_call_async_signal_handler (struct async_signal_handler *handler, 115 int immediate_p); 116 117 /* Create and register an asynchronous event source in the event loop, 118 and set PROC as its callback. CLIENT_DATA is passed as argument to 119 PROC upon its invocation. Returns a pointer to an opaque structure 120 used to mark as ready and to later delete this event source from 121 the event loop. */ 122 extern struct async_event_handler * 123 create_async_event_handler (async_event_handler_func *proc, 124 gdb_client_data client_data); 125 126 /* Remove the event source pointed by HANDLER_PTR created by 127 CREATE_ASYNC_EVENT_HANDLER from the event loop, and release it. */ 128 extern void 129 delete_async_event_handler (struct async_event_handler **handler_ptr); 130 131 /* Call the handler from HANDLER the next time through the event 132 loop. */ 133 extern void mark_async_event_handler (struct async_event_handler *handler); 134