| 1 | /* blockinput.h - interface to blocking complicated interrupt-driven input. |
| 2 | Copyright (C) 1989, 1993, 2001-2012 Free Software Foundation, Inc. |
| 3 | |
| 4 | This file is part of GNU Emacs. |
| 5 | |
| 6 | GNU Emacs is free software: you can redistribute it and/or modify |
| 7 | it under the terms of the GNU General Public License as published by |
| 8 | the Free Software Foundation, either version 3 of the License, or |
| 9 | (at your option) any later version. |
| 10 | |
| 11 | GNU Emacs is distributed in the hope that it will be useful, |
| 12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 14 | GNU General Public License for more details. |
| 15 | |
| 16 | You should have received a copy of the GNU General Public License |
| 17 | along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */ |
| 18 | |
| 19 | #ifndef EMACS_BLOCKINPUT_H |
| 20 | #define EMACS_BLOCKINPUT_H |
| 21 | |
| 22 | #include "atimer.h" |
| 23 | |
| 24 | /* When Emacs is using signal-driven input, the processing of those |
| 25 | input signals can get pretty hairy. For example, when Emacs is |
| 26 | running under X windows, handling an input signal can entail |
| 27 | retrieving events from the X event queue, or making other X calls. |
| 28 | |
| 29 | If an input signal occurs while Emacs is in the midst of some |
| 30 | non-reentrant code, and the signal processing invokes that same |
| 31 | code, we lose. For example, malloc and the Xlib functions aren't |
| 32 | usually re-entrant, and both are used by the X input signal handler |
| 33 | - if we try to process an input signal in the midst of executing |
| 34 | any of these functions, we'll lose. |
| 35 | |
| 36 | To avoid this, we make the following requirements: |
| 37 | |
| 38 | * Everyone must evaluate BLOCK_INPUT before entering these functions, |
| 39 | and then call UNBLOCK_INPUT after performing them. Calls |
| 40 | BLOCK_INPUT and UNBLOCK_INPUT may be nested. |
| 41 | |
| 42 | * Any complicated interrupt handling code should test |
| 43 | interrupt_input_blocked, and put off its work until later. |
| 44 | |
| 45 | * If the interrupt handling code wishes, it may set |
| 46 | interrupt_input_pending to a non-zero value. If that flag is set |
| 47 | when input becomes unblocked, UNBLOCK_INPUT will send a new SIGIO. */ |
| 48 | |
| 49 | extern volatile int interrupt_input_blocked; |
| 50 | |
| 51 | /* Nonzero means an input interrupt has arrived |
| 52 | during the current critical section. */ |
| 53 | extern int interrupt_input_pending; |
| 54 | |
| 55 | |
| 56 | /* Non-zero means asynchronous timers should be run when input is |
| 57 | unblocked. */ |
| 58 | |
| 59 | extern int pending_atimers; |
| 60 | |
| 61 | |
| 62 | /* Begin critical section. */ |
| 63 | #define BLOCK_INPUT (interrupt_input_blocked++) |
| 64 | |
| 65 | /* End critical section. |
| 66 | |
| 67 | If doing signal-driven input, and a signal came in when input was |
| 68 | blocked, reinvoke the signal handler now to deal with it. |
| 69 | |
| 70 | We used to have two possible definitions of this macro - one for |
| 71 | when SIGIO was #defined, and one for when it wasn't; when SIGIO |
| 72 | wasn't #defined, we wouldn't bother to check if we should re-invoke |
| 73 | the signal handler. But that doesn't work very well; some of the |
| 74 | files which use this macro don't #include the right files to get |
| 75 | SIGIO. |
| 76 | |
| 77 | So, we always test interrupt_input_pending now; that's not too |
| 78 | expensive, and it'll never get set if we don't need to resignal. */ |
| 79 | |
| 80 | #define UNBLOCK_INPUT \ |
| 81 | do \ |
| 82 | { \ |
| 83 | --interrupt_input_blocked; \ |
| 84 | if (interrupt_input_blocked == 0) \ |
| 85 | { \ |
| 86 | if (interrupt_input_pending) \ |
| 87 | reinvoke_input_signal (); \ |
| 88 | if (pending_atimers) \ |
| 89 | do_pending_atimers (); \ |
| 90 | } \ |
| 91 | else if (interrupt_input_blocked < 0) \ |
| 92 | abort (); \ |
| 93 | } \ |
| 94 | while (0) |
| 95 | |
| 96 | /* Undo any number of BLOCK_INPUT calls, |
| 97 | and also reinvoke any pending signal. */ |
| 98 | |
| 99 | #define TOTALLY_UNBLOCK_INPUT \ |
| 100 | do if (interrupt_input_blocked != 0) \ |
| 101 | { \ |
| 102 | interrupt_input_blocked = 1; \ |
| 103 | UNBLOCK_INPUT; \ |
| 104 | } \ |
| 105 | while (0) |
| 106 | |
| 107 | /* Undo any number of BLOCK_INPUT calls down to level LEVEL, |
| 108 | and also (if the level is now 0) reinvoke any pending signal. */ |
| 109 | |
| 110 | #define UNBLOCK_INPUT_TO(LEVEL) \ |
| 111 | do \ |
| 112 | { \ |
| 113 | interrupt_input_blocked = (LEVEL) + 1; \ |
| 114 | UNBLOCK_INPUT; \ |
| 115 | } \ |
| 116 | while (0) |
| 117 | |
| 118 | #define UNBLOCK_INPUT_RESIGNAL UNBLOCK_INPUT |
| 119 | |
| 120 | /* In critical section ? */ |
| 121 | #define INPUT_BLOCKED_P (interrupt_input_blocked > 0) |
| 122 | |
| 123 | /* Defined in keyboard.c */ |
| 124 | extern void reinvoke_input_signal (void); |
| 125 | |
| 126 | #endif /* EMACS_BLOCKINPUT_H */ |
| 127 | |