428
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1 /* Copyright (C) 1985, 86, 87, 93, 94, 96 Free Software Foundation, Inc.
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771
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2 Copyright (C) 2001 Ben Wing.
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428
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3
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613
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4 This file is part of XEmacs.
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428
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5
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613
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6 XEmacs is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2, or (at your option)
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9 any later version.
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10
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613
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11 XEmacs is distributed in the hope that it will be useful,
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428
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
|
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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613
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17 along with XEmacs; see the file COPYING. If not, write to
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18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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19 Boston, MA 02111-1307, USA. */
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20
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21 /* Synced with FSF 20.2 */
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22
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23 #include <config.h>
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24 #include "lisp.h"
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25
|
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26 #include "buffer.h"
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27 #include <paths.h>
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28
|
859
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29 #include "sysdir.h"
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428
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30 #include "sysfile.h"
|
859
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31 #include "sysproc.h" /* for qxe_getpid() */
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428
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32 #include "syspwd.h"
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859
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33 #include "syssignal.h" /* for kill. */
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428
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34
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35 Lisp_Object Qask_user_about_supersession_threat;
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36 Lisp_Object Qask_user_about_lock;
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444
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37 int inhibit_clash_detection;
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428
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38
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39 #ifdef CLASH_DETECTION
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442
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40
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428
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41 /* The strategy: to lock a file FN, create a symlink .#FN in FN's
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42 directory, with link data `user@host.pid'. This avoids a single
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43 mount (== failure) point for lock files.
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44
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45 When the host in the lock data is the current host, we can check if
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46 the pid is valid with kill.
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442
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47
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428
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48 Otherwise, we could look at a separate file that maps hostnames to
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49 reboot times to see if the remote pid can possibly be valid, since we
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50 don't want Emacs to have to communicate via pipes or sockets or
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51 whatever to other processes, either locally or remotely; rms says
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52 that's too unreliable. Hence the separate file, which could
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53 theoretically be updated by daemons running separately -- but this
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54 whole idea is unimplemented; in practice, at least in our
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55 environment, it seems such stale locks arise fairly infrequently, and
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56 Emacs' standard methods of dealing with clashes suffice.
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57
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58 We use symlinks instead of normal files because (1) they can be
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59 stored more efficiently on the filesystem, since the kernel knows
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60 they will be small, and (2) all the info about the lock can be read
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61 in a single system call (readlink). Although we could use regular
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62 files to be useful on old systems lacking symlinks, nowadays
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63 virtually all such systems are probably single-user anyway, so it
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64 didn't seem worth the complication.
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65
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66 Similarly, we don't worry about a possible 14-character limit on
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67 file names, because those are all the same systems that don't have
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68 symlinks.
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442
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69
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428
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70 This is compatible with the locking scheme used by Interleaf (which
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71 has contributed this implementation for Emacs), and was designed by
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72 Ethan Jacobson, Kimbo Mundy, and others.
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442
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73
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428
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74 --karl@cs.umb.edu/karl@hq.ileaf.com. */
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75
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76
|
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77 /* Here is the structure that stores information about a lock. */
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78
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79 typedef struct
|
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80 {
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867
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81 Ibyte *user;
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82 Ibyte *host;
|
647
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83 pid_t pid;
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428
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84 } lock_info_type;
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85
|
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86 /* When we read the info back, we might need this much more,
|
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87 enough for decimal representation plus null. */
|
647
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88 #define LOCK_PID_MAX (4 * sizeof (pid_t))
|
428
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89
|
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90 /* Free the two dynamically-allocated pieces in PTR. */
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91 #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
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92
|
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93 /* Write the name of the lock file for FN into LFNAME. Length will be
|
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94 that of FN plus two more for the leading `.#' plus one for the null. */
|
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95 #define MAKE_LOCK_NAME(lock, file) \
|
867
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96 (lock = (Ibyte *) ALLOCA (XSTRING_LENGTH (file) + 2 + 1), \
|
771
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97 fill_in_lock_file_name (lock, file))
|
428
|
98
|
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99 static void
|
867
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100 fill_in_lock_file_name (Ibyte *lockfile, Lisp_Object fn)
|
428
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101 {
|
867
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102 Ibyte *file_name = XSTRING_DATA (fn);
|
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103 Ibyte *p;
|
647
|
104 Bytecount dirlen;
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428
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105
|
442
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106 for (p = file_name + XSTRING_LENGTH (fn) - 1;
|
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107 p > file_name && !IS_ANY_SEP (p[-1]);
|
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108 p--)
|
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109 ;
|
|
110 dirlen = p - file_name;
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428
|
111
|
442
|
112 memcpy (lockfile, file_name, dirlen);
|
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113 p = lockfile + dirlen;
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114 *(p++) = '.';
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115 *(p++) = '#';
|
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116 memcpy (p, file_name + dirlen, XSTRING_LENGTH (fn) - dirlen + 1);
|
428
|
117 }
|
|
118
|
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119 /* Lock the lock file named LFNAME.
|
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120 If FORCE is nonzero, we do so even if it is already locked.
|
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121 Return 1 if successful, 0 if not. */
|
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122
|
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123 static int
|
867
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124 lock_file_1 (Ibyte *lfname, int force)
|
428
|
125 {
|
442
|
126 /* Does not GC. */
|
|
127 int err;
|
867
|
128 Ibyte *lock_info_str;
|
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129 Ibyte *host_name;
|
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130 Ibyte *user_name = user_login_name (NULL);
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428
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131
|
442
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132 if (user_name == NULL)
|
867
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133 user_name = (Ibyte *) "";
|
442
|
134
|
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135 if (STRINGP (Vsystem_name))
|
771
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136 host_name = XSTRING_DATA (Vsystem_name);
|
428
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137 else
|
867
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138 host_name = (Ibyte *) "";
|
442
|
139
|
771
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140 lock_info_str =
|
867
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141 (Ibyte *) ALLOCA (qxestrlen (user_name) + qxestrlen (host_name)
|
771
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142 + LOCK_PID_MAX + 5);
|
428
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143
|
771
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144 qxesprintf (lock_info_str, "%s@%s.%d", user_name, host_name, qxe_getpid ());
|
428
|
145
|
771
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146 err = qxe_symlink (lock_info_str, lfname);
|
442
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147 if (err != 0 && errno == EEXIST && force)
|
428
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148 {
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771
|
149 qxe_unlink (lfname);
|
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150 err = qxe_symlink (lock_info_str, lfname);
|
428
|
151 }
|
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152
|
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153 return err == 0;
|
|
154 }
|
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155
|
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156 /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete,
|
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157 1 if another process owns it (and set OWNER (if non-null) to info),
|
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158 2 if the current process owns it,
|
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159 or -1 if something is wrong with the locking mechanism. */
|
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160
|
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161 static int
|
867
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162 current_lock_owner (lock_info_type *owner, Ibyte *lfname)
|
428
|
163 {
|
442
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164 /* Does not GC. */
|
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165 int len, ret;
|
428
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166 int local_owner = 0;
|
867
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167 Ibyte *at, *dot;
|
|
168 Ibyte *lfinfo = 0;
|
428
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169 int bufsize = 50;
|
|
170 /* Read arbitrarily-long contents of symlink. Similar code in
|
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171 file-symlink-p in fileio.c. */
|
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172 do
|
|
173 {
|
|
174 bufsize *= 2;
|
867
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175 lfinfo = (Ibyte *) xrealloc (lfinfo, bufsize);
|
771
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176 len = qxe_readlink (lfname, lfinfo, bufsize);
|
428
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177 }
|
|
178 while (len >= bufsize);
|
442
|
179
|
428
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180 /* If nonexistent lock file, all is well; otherwise, got strange error. */
|
|
181 if (len == -1)
|
|
182 {
|
|
183 xfree (lfinfo);
|
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184 return errno == ENOENT ? 0 : -1;
|
|
185 }
|
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186
|
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187 /* Link info exists, so `len' is its length. Null terminate. */
|
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188 lfinfo[len] = 0;
|
442
|
189
|
428
|
190 /* Even if the caller doesn't want the owner info, we still have to
|
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191 read it to determine return value, so allocate it. */
|
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192 if (!owner)
|
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193 {
|
851
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194 owner = (lock_info_type *) ALLOCA (sizeof (lock_info_type));
|
428
|
195 local_owner = 1;
|
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196 }
|
442
|
197
|
428
|
198 /* Parse USER@HOST.PID. If can't parse, return -1. */
|
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199 /* The USER is everything before the first @. */
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771
|
200 at = qxestrchr (lfinfo, '@');
|
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201 dot = qxestrrchr (lfinfo, '.');
|
428
|
202 if (!at || !dot) {
|
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203 xfree (lfinfo);
|
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204 return -1;
|
|
205 }
|
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206 len = at - lfinfo;
|
867
|
207 owner->user = (Ibyte *) xmalloc (len + 1);
|
771
|
208 qxestrncpy (owner->user, lfinfo, len);
|
428
|
209 owner->user[len] = 0;
|
442
|
210
|
428
|
211 /* The PID is everything after the last `.'. */
|
867
|
212 owner->pid = atoi ((CIbyte *) dot + 1);
|
428
|
213
|
|
214 /* The host is everything in between. */
|
|
215 len = dot - at - 1;
|
867
|
216 owner->host = (Ibyte *) xmalloc (len + 1);
|
771
|
217 qxestrncpy (owner->host, at + 1, len);
|
428
|
218 owner->host[len] = 0;
|
|
219
|
|
220 /* We're done looking at the link info. */
|
|
221 xfree (lfinfo);
|
442
|
222
|
428
|
223 /* On current host? */
|
442
|
224 if (STRINGP (Fsystem_name ())
|
771
|
225 && qxestrcmp (owner->host, XSTRING_DATA (Fsystem_name ())) == 0)
|
428
|
226 {
|
771
|
227 if (owner->pid == qxe_getpid ())
|
428
|
228 ret = 2; /* We own it. */
|
|
229 else if (owner->pid > 0
|
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230 && (kill (owner->pid, 0) >= 0 || errno == EPERM))
|
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231 ret = 1; /* An existing process on this machine owns it. */
|
|
232 /* The owner process is dead or has a strange pid (<=0), so try to
|
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233 zap the lockfile. */
|
771
|
234 else if (qxe_unlink (lfname) < 0)
|
428
|
235 ret = -1;
|
|
236 else
|
|
237 ret = 0;
|
|
238 }
|
|
239 else
|
|
240 { /* If we wanted to support the check for stale locks on remote machines,
|
|
241 here's where we'd do it. */
|
|
242 ret = 1;
|
|
243 }
|
442
|
244
|
428
|
245 /* Avoid garbage. */
|
|
246 if (local_owner || ret <= 0)
|
|
247 {
|
|
248 FREE_LOCK_INFO (*owner);
|
|
249 }
|
|
250 return ret;
|
|
251 }
|
|
252
|
|
253 /* Lock the lock named LFNAME if possible.
|
|
254 Return 0 in that case.
|
|
255 Return positive if some other process owns the lock, and info about
|
|
256 that process in CLASHER.
|
|
257 Return -1 if cannot lock for any other reason. */
|
|
258
|
|
259 static int
|
867
|
260 lock_if_free (lock_info_type *clasher, Ibyte *lfname)
|
428
|
261 {
|
442
|
262 /* Does not GC. */
|
867
|
263 if (lock_file_1 ((Ibyte *) lfname, 0) == 0)
|
428
|
264 {
|
|
265 int locker;
|
|
266
|
|
267 if (errno != EEXIST)
|
|
268 return -1;
|
442
|
269
|
428
|
270 locker = current_lock_owner (clasher, lfname);
|
|
271 if (locker == 2)
|
|
272 {
|
|
273 FREE_LOCK_INFO (*clasher);
|
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274 return 0; /* We ourselves locked it. */
|
|
275 }
|
|
276 else if (locker == 1)
|
|
277 return 1; /* Someone else has it. */
|
|
278
|
|
279 return -1; /* Something's wrong. */
|
|
280 }
|
|
281 return 0;
|
|
282 }
|
|
283
|
|
284 /* lock_file locks file FN,
|
|
285 meaning it serves notice on the world that you intend to edit that file.
|
|
286 This should be done only when about to modify a file-visiting
|
|
287 buffer previously unmodified.
|
|
288 Do not (normally) call this for a buffer already modified,
|
|
289 as either the file is already locked, or the user has already
|
|
290 decided to go ahead without locking.
|
|
291
|
|
292 When this returns, either the lock is locked for us,
|
|
293 or the user has said to go ahead without locking.
|
|
294
|
|
295 If the file is locked by someone else, this calls
|
|
296 ask-user-about-lock (a Lisp function) with two arguments,
|
|
297 the file name and info about the user who did the locking.
|
|
298 This function can signal an error, or return t meaning
|
|
299 take away the lock, or return nil meaning ignore the lock. */
|
|
300
|
|
301 void
|
|
302 lock_file (Lisp_Object fn)
|
|
303 {
|
442
|
304 /* This function can GC. GC checked 7-11-00 ben */
|
428
|
305 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
306 mean nasty things with pointy teeth. If you call this make sure
|
|
307 you protect things right. */
|
442
|
308 /* Somebody updated the code in this function and removed the previous
|
428
|
309 comment. -slb */
|
|
310
|
|
311 register Lisp_Object attack, orig_fn;
|
867
|
312 register Ibyte *lfname, *locker;
|
428
|
313 lock_info_type lock_info;
|
444
|
314 struct gcpro gcpro1, gcpro2, gcpro3;
|
|
315 Lisp_Object old_current_buffer;
|
428
|
316 Lisp_Object subject_buf;
|
|
317
|
444
|
318 if (inhibit_clash_detection)
|
|
319 return;
|
|
320
|
793
|
321 old_current_buffer = wrap_buffer (current_buffer);
|
446
|
322 subject_buf = Qnil;
|
444
|
323 GCPRO3 (fn, subject_buf, old_current_buffer);
|
428
|
324 orig_fn = fn;
|
|
325 fn = Fexpand_file_name (fn, Qnil);
|
|
326
|
|
327 /* Create the name of the lock-file for file fn */
|
|
328 MAKE_LOCK_NAME (lfname, fn);
|
|
329
|
|
330 /* See if this file is visited and has changed on disk since it was
|
|
331 visited. */
|
|
332 {
|
|
333 subject_buf = get_truename_buffer (orig_fn);
|
|
334 if (!NILP (subject_buf)
|
|
335 && NILP (Fverify_visited_file_modtime (subject_buf))
|
|
336 && !NILP (Ffile_exists_p (fn)))
|
442
|
337 call1_in_buffer (XBUFFER (subject_buf),
|
|
338 Qask_user_about_supersession_threat, fn);
|
428
|
339 }
|
|
340
|
|
341 /* Try to lock the lock. */
|
444
|
342 if (current_buffer != XBUFFER (old_current_buffer)
|
|
343 || lock_if_free (&lock_info, lfname) <= 0)
|
|
344 /* Return now if we have locked it, or if lock creation failed
|
|
345 or current buffer is killed. */
|
428
|
346 goto done;
|
|
347
|
|
348 /* Else consider breaking the lock */
|
867
|
349 locker = (Ibyte *) ALLOCA (qxestrlen (lock_info.user)
|
771
|
350 + qxestrlen (lock_info.host)
|
|
351 + LOCK_PID_MAX + 9);
|
|
352 qxesprintf (locker, "%s@%s (pid %d)", lock_info.user, lock_info.host,
|
|
353 lock_info.pid);
|
428
|
354 FREE_LOCK_INFO (lock_info);
|
442
|
355
|
428
|
356 attack = call2_in_buffer (BUFFERP (subject_buf) ? XBUFFER (subject_buf) :
|
|
357 current_buffer, Qask_user_about_lock , fn,
|
771
|
358 build_intstring (locker));
|
444
|
359 if (!NILP (attack) && current_buffer == XBUFFER (old_current_buffer))
|
428
|
360 /* User says take the lock */
|
|
361 {
|
|
362 lock_file_1 (lfname, 1);
|
|
363 goto done;
|
|
364 }
|
|
365 /* User says ignore the lock */
|
|
366 done:
|
|
367 UNGCPRO;
|
|
368 }
|
|
369
|
|
370 void
|
|
371 unlock_file (Lisp_Object fn)
|
|
372 {
|
442
|
373 /* This can GC */
|
867
|
374 register Ibyte *lfname;
|
442
|
375 struct gcpro gcpro1;
|
|
376
|
|
377 GCPRO1 (fn);
|
428
|
378
|
|
379 fn = Fexpand_file_name (fn, Qnil);
|
|
380
|
|
381 MAKE_LOCK_NAME (lfname, fn);
|
|
382
|
|
383 if (current_lock_owner (0, lfname) == 2)
|
771
|
384 qxe_unlink (lfname);
|
442
|
385
|
|
386 UNGCPRO;
|
428
|
387 }
|
|
388
|
|
389 void
|
442
|
390 unlock_all_files (void)
|
428
|
391 {
|
|
392 register Lisp_Object tail;
|
|
393
|
434
|
394 for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail))
|
428
|
395 {
|
442
|
396 struct buffer *b = XBUFFER (XCDR (XCAR (tail)));
|
428
|
397 if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
|
|
398 unlock_file (b->file_truename);
|
|
399 }
|
|
400 }
|
|
401
|
|
402 DEFUN ("lock-buffer", Flock_buffer, 0, 1, 0, /*
|
442
|
403 Lock FILE, if current buffer is modified.
|
|
404 FILE defaults to current buffer's visited file,
|
428
|
405 or else nothing is done if current buffer isn't visiting a file.
|
|
406 */
|
442
|
407 (file))
|
428
|
408 {
|
|
409 if (NILP (file))
|
|
410 file = current_buffer->file_truename;
|
|
411 CHECK_STRING (file);
|
|
412 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
|
|
413 && !NILP (file))
|
|
414 lock_file (file);
|
|
415 return Qnil;
|
|
416 }
|
|
417
|
|
418 DEFUN ("unlock-buffer", Funlock_buffer, 0, 0, 0, /*
|
|
419 Unlock the file visited in the current buffer,
|
|
420 if it should normally be locked.
|
|
421 */
|
|
422 ())
|
|
423 {
|
|
424 /* This function can GC */
|
|
425 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
426 mean nasty things with pointy teeth. If you call this make sure
|
|
427 you protect things right. */
|
|
428
|
|
429 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
|
|
430 && STRINGP (current_buffer->file_truename))
|
|
431 unlock_file (current_buffer->file_truename);
|
|
432 return Qnil;
|
|
433 }
|
|
434
|
|
435 /* Unlock the file visited in buffer BUFFER. */
|
|
436
|
|
437
|
|
438 void
|
|
439 unlock_buffer (struct buffer *buffer)
|
|
440 {
|
|
441 /* This function can GC */
|
|
442 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
443 mean nasty things with pointy teeth. If you call this make sure
|
|
444 you protect things right. */
|
|
445 if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer)
|
|
446 && STRINGP (buffer->file_truename))
|
|
447 unlock_file (buffer->file_truename);
|
|
448 }
|
|
449
|
|
450 DEFUN ("file-locked-p", Ffile_locked_p, 0, 1, 0, /*
|
442
|
451 Return nil if the FILENAME is not locked,
|
428
|
452 t if it is locked by you, else a string of the name of the locker.
|
|
453 */
|
442
|
454 (filename))
|
428
|
455 {
|
|
456 Lisp_Object ret;
|
867
|
457 register Ibyte *lfname;
|
428
|
458 int owner;
|
|
459 lock_info_type locker;
|
442
|
460 struct gcpro gcpro1;
|
|
461
|
|
462 GCPRO1 (filename);
|
428
|
463
|
|
464 filename = Fexpand_file_name (filename, Qnil);
|
|
465
|
|
466 MAKE_LOCK_NAME (lfname, filename);
|
|
467
|
|
468 owner = current_lock_owner (&locker, lfname);
|
|
469 if (owner <= 0)
|
|
470 ret = Qnil;
|
|
471 else if (owner == 2)
|
|
472 ret = Qt;
|
|
473 else
|
771
|
474 ret = build_intstring (locker.user);
|
428
|
475
|
|
476 if (owner > 0)
|
|
477 FREE_LOCK_INFO (locker);
|
|
478
|
442
|
479 UNGCPRO;
|
|
480
|
428
|
481 return ret;
|
|
482 }
|
|
483
|
|
484
|
|
485 /* Initialization functions. */
|
|
486
|
|
487 void
|
|
488 syms_of_filelock (void)
|
|
489 {
|
|
490 /* This function can GC */
|
|
491 DEFSUBR (Funlock_buffer);
|
|
492 DEFSUBR (Flock_buffer);
|
|
493 DEFSUBR (Ffile_locked_p);
|
|
494
|
563
|
495 DEFSYMBOL (Qask_user_about_supersession_threat);
|
|
496 DEFSYMBOL (Qask_user_about_lock);
|
428
|
497 }
|
|
498
|
444
|
499 void
|
|
500 vars_of_filelock (void)
|
|
501 {
|
|
502 DEFVAR_BOOL ("inhibit-clash-detection", &inhibit_clash_detection /*
|
|
503 Non-nil inhibits creation of lock file to detect clash.
|
|
504 */);
|
|
505 inhibit_clash_detection = 0;
|
|
506 }
|
428
|
507
|
|
508 #endif /* CLASH_DETECTION */
|