1 /* Definitions used by the GDB event loop. 2 Copyright (C) 1999, 2000, 2007, 2008, 2009, 2010, 2011 3 Free Software Foundation, Inc. 4 Written by Elena Zannoni <ezannoni@cygnus.com> of Cygnus Solutions. 5 6 This file is part of GDB. 7 8 This program is free software; you can redistribute it and/or modify 9 it under the terms of the GNU General Public License as published by 10 the Free Software Foundation; either version 3 of the License, or 11 (at your option) any later version. 12 13 This program is distributed in the hope that it will be useful, 14 but WITHOUT ANY WARRANTY; without even the implied warranty of 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 GNU General Public License for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 20 21 /* An event loop listens for events from multiple event sources. When 22 an event arrives, it is queued and processed by calling the 23 appropriate event handler. The event loop then continues to listen 24 for more events. An event loop completes when there are no event 25 sources to listen on. External event sources can be plugged into 26 the loop. 27 28 There are 4 main components: 29 - a list of file descriptors to be monitored, GDB_NOTIFIER. 30 - a list of asynchronous event sources to be monitored, 31 ASYNC_EVENT_HANDLER_LIST. 32 - a list of events that have occurred, EVENT_QUEUE. 33 - a list of signal handling functions, SIGHANDLER_LIST. 34 35 GDB_NOTIFIER keeps track of the file descriptor based event 36 sources. ASYNC_EVENT_HANDLER_LIST keeps track of asynchronous 37 event sources that are signalled by some component of gdb, usually 38 a target_ops instance. Event sources for gdb are currently the UI 39 and the target. Gdb communicates with the command line user 40 interface via the readline library and usually communicates with 41 remote targets via a serial port. Serial ports are represented in 42 GDB as file descriptors and select/poll calls. For native targets 43 instead, the communication varies across operating system debug 44 APIs, but usually consists of calls to ptrace and waits (via 45 signals) or calls to poll/select (via file descriptors). In the 46 current gdb, the code handling events related to the target resides 47 in wait_for_inferior for synchronous targets; or, for asynchronous 48 capable targets, by having the target register either a target 49 controlled file descriptor and/or an asynchronous event source in 50 the event loop, with the fetch_inferior_event function as the event 51 callback. In both the synchronous and asynchronous cases, usually 52 the target event is collected through the target_wait interface. 53 The target is free to install other event sources in the event loop 54 if it so requires. 55 56 EVENT_QUEUE keeps track of the events that have happened during the 57 last iteration of the event loop, and need to be processed. An 58 event is represented by a procedure to be invoked in order to 59 process the event. The queue is scanned head to tail. If the 60 event of interest is a change of state in a file descriptor, then a 61 call to poll or select will be made to detect it. 62 63 If the events generate signals, they are also queued by special 64 functions that are invoked through traditional signal handlers. 65 The actions to be taken is response to such events will be executed 66 when the SIGHANDLER_LIST is scanned, the next time through the 67 infinite loop. 68 69 Corollary tasks are the creation and deletion of event sources. */ 70 71 typedef void *gdb_client_data; 72 struct async_signal_handler; 73 struct async_event_handler; 74 typedef void (handler_func) (int, gdb_client_data); 75 typedef void (sig_handler_func) (gdb_client_data); 76 typedef void (async_event_handler_func) (gdb_client_data); 77 typedef void (timer_handler_func) (gdb_client_data); 78 79 /* Where to add an event onto the event queue, by queue_event. */ 80 typedef enum 81 { 82 /* Add at tail of queue. It will be processed in first in first 83 out order. */ 84 TAIL, 85 /* Add at head of queue. It will be processed in last in first 86 out order. */ 87 HEAD 88 } 89 queue_position; 90 91 /* Exported functions from event-loop.c */ 92 93 extern void start_event_loop (void); 94 extern int gdb_do_one_event (void *data); 95 extern void delete_file_handler (int fd); 96 extern void add_file_handler (int fd, handler_func *proc, 97 gdb_client_data client_data); 98 extern struct async_signal_handler * 99 create_async_signal_handler (sig_handler_func *proc, 100 gdb_client_data client_data); 101 extern void delete_async_signal_handler (struct async_signal_handler **); 102 extern int create_timer (int milliseconds, 103 timer_handler_func *proc, 104 gdb_client_data client_data); 105 extern void delete_timer (int id); 106 107 /* Call the handler from HANDLER immediately. This function 108 runs signal handlers when returning to the event loop would be too 109 slow. Do not call this directly; use gdb_call_async_signal_handler, 110 below, with IMMEDIATE_P == 1. */ 111 void call_async_signal_handler (struct async_signal_handler *handler); 112 113 /* Call the handler from HANDLER the next time through the event loop. 114 Do not call this directly; use gdb_call_async_signal_handler, 115 below, with IMMEDIATE_P == 0. */ 116 void mark_async_signal_handler (struct async_signal_handler *handler); 117 118 /* Wrapper for the body of signal handlers. Call this function from 119 any SIGINT handler which needs to access GDB data structures or 120 escape via longjmp. If IMMEDIATE_P is set, this triggers either 121 immediately (for POSIX platforms), or from gdb_select (for 122 MinGW). If IMMEDIATE_P is clear, the handler will run the next 123 time we return to the event loop and any current select calls 124 will be interrupted. */ 125 126 void gdb_call_async_signal_handler (struct async_signal_handler *handler, 127 int immediate_p); 128 129 /* Create and register an asynchronous event source in the event loop, 130 and set PROC as its callback. CLIENT_DATA is passed as argument to 131 PROC upon its invocation. Returns a pointer to an opaque structure 132 used to mark as ready and to later delete this event source from 133 the event loop. */ 134 extern struct async_event_handler * 135 create_async_event_handler (async_event_handler_func *proc, 136 gdb_client_data client_data); 137 138 /* Remove the event source pointed by HANDLER_PTR created by 139 CREATE_ASYNC_EVENT_HANDLER from the event loop, and release it. */ 140 extern void 141 delete_async_event_handler (struct async_event_handler **handler_ptr); 142 143 /* Call the handler from HANDLER the next time through the event 144 loop. */ 145 extern void mark_async_event_handler (struct async_event_handler *handler); 146