|
428
|
1 /* Copyright (C) 1985, 86, 87, 93, 94, 96 Free Software Foundation, Inc.
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771
|
2 Copyright (C) 2001 Ben Wing.
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428
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3
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613
|
4 This file is part of XEmacs.
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428
|
5
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613
|
6 XEmacs is free software; you can redistribute it and/or modify
|
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428
|
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
|
11 XEmacs is distributed in the hope that it will be useful,
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428
|
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
|
|
613
|
17 along with XEmacs; see the file COPYING. If not, write to
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428
|
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
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29 #include "sysfile.h"
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30 #include "sysdir.h"
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31 #include "syspwd.h"
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854
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32 #include "syssignal.h" /* for kill. Always include before sysproc.h
|
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|
33 -- didier */
|
|
771
|
34 #include "sysproc.h" /* for qxe_getpid() */
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428
|
35
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36 Lisp_Object Qask_user_about_supersession_threat;
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37 Lisp_Object Qask_user_about_lock;
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444
|
38 int inhibit_clash_detection;
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|
428
|
39
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|
|
40 #ifdef CLASH_DETECTION
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442
|
41
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428
|
42 /* The strategy: to lock a file FN, create a symlink .#FN in FN's
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43 directory, with link data `user@host.pid'. This avoids a single
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44 mount (== failure) point for lock files.
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45
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46 When the host in the lock data is the current host, we can check if
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47 the pid is valid with kill.
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|
442
|
48
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428
|
49 Otherwise, we could look at a separate file that maps hostnames to
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|
50 reboot times to see if the remote pid can possibly be valid, since we
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51 don't want Emacs to have to communicate via pipes or sockets or
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52 whatever to other processes, either locally or remotely; rms says
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53 that's too unreliable. Hence the separate file, which could
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54 theoretically be updated by daemons running separately -- but this
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55 whole idea is unimplemented; in practice, at least in our
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56 environment, it seems such stale locks arise fairly infrequently, and
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57 Emacs' standard methods of dealing with clashes suffice.
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58
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59 We use symlinks instead of normal files because (1) they can be
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60 stored more efficiently on the filesystem, since the kernel knows
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61 they will be small, and (2) all the info about the lock can be read
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62 in a single system call (readlink). Although we could use regular
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63 files to be useful on old systems lacking symlinks, nowadays
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64 virtually all such systems are probably single-user anyway, so it
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65 didn't seem worth the complication.
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66
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67 Similarly, we don't worry about a possible 14-character limit on
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68 file names, because those are all the same systems that don't have
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69 symlinks.
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|
442
|
70
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428
|
71 This is compatible with the locking scheme used by Interleaf (which
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72 has contributed this implementation for Emacs), and was designed by
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73 Ethan Jacobson, Kimbo Mundy, and others.
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442
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74
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428
|
75 --karl@cs.umb.edu/karl@hq.ileaf.com. */
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76
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77
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78 /* Here is the structure that stores information about a lock. */
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79
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80 typedef struct
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81 {
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771
|
82 Intbyte *user;
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83 Intbyte *host;
|
|
647
|
84 pid_t pid;
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|
428
|
85 } lock_info_type;
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86
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87 /* When we read the info back, we might need this much more,
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|
88 enough for decimal representation plus null. */
|
|
647
|
89 #define LOCK_PID_MAX (4 * sizeof (pid_t))
|
|
428
|
90
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|
|
91 /* Free the two dynamically-allocated pieces in PTR. */
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92 #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0)
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93
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94 /* Write the name of the lock file for FN into LFNAME. Length will be
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95 that of FN plus two more for the leading `.#' plus one for the null. */
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96 #define MAKE_LOCK_NAME(lock, file) \
|
|
851
|
97 (lock = (Intbyte *) ALLOCA (XSTRING_LENGTH (file) + 2 + 1), \
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|
771
|
98 fill_in_lock_file_name (lock, file))
|
|
428
|
99
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100 static void
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665
|
101 fill_in_lock_file_name (Intbyte *lockfile, Lisp_Object fn)
|
|
428
|
102 {
|
|
665
|
103 Intbyte *file_name = XSTRING_DATA (fn);
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|
104 Intbyte *p;
|
|
647
|
105 Bytecount dirlen;
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|
428
|
106
|
|
442
|
107 for (p = file_name + XSTRING_LENGTH (fn) - 1;
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108 p > file_name && !IS_ANY_SEP (p[-1]);
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109 p--)
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110 ;
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111 dirlen = p - file_name;
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|
428
|
112
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442
|
113 memcpy (lockfile, file_name, dirlen);
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114 p = lockfile + dirlen;
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115 *(p++) = '.';
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|
116 *(p++) = '#';
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117 memcpy (p, file_name + dirlen, XSTRING_LENGTH (fn) - dirlen + 1);
|
|
428
|
118 }
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119
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120 /* Lock the lock file named LFNAME.
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121 If FORCE is nonzero, we do so even if it is already locked.
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122 Return 1 if successful, 0 if not. */
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123
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|
124 static int
|
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771
|
125 lock_file_1 (Intbyte *lfname, int force)
|
|
428
|
126 {
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|
442
|
127 /* Does not GC. */
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|
128 int err;
|
|
771
|
129 Intbyte *lock_info_str;
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|
|
130 Intbyte *host_name;
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|
131 Intbyte *user_name = user_login_name (NULL);
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|
428
|
132
|
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442
|
133 if (user_name == NULL)
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771
|
134 user_name = (Intbyte *) "";
|
|
442
|
135
|
|
|
136 if (STRINGP (Vsystem_name))
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|
771
|
137 host_name = XSTRING_DATA (Vsystem_name);
|
|
428
|
138 else
|
|
771
|
139 host_name = (Intbyte *) "";
|
|
442
|
140
|
|
771
|
141 lock_info_str =
|
|
851
|
142 (Intbyte *) ALLOCA (qxestrlen (user_name) + qxestrlen (host_name)
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|
771
|
143 + LOCK_PID_MAX + 5);
|
|
428
|
144
|
|
771
|
145 qxesprintf (lock_info_str, "%s@%s.%d", user_name, host_name, qxe_getpid ());
|
|
428
|
146
|
|
771
|
147 err = qxe_symlink (lock_info_str, lfname);
|
|
442
|
148 if (err != 0 && errno == EEXIST && force)
|
|
428
|
149 {
|
|
771
|
150 qxe_unlink (lfname);
|
|
|
151 err = qxe_symlink (lock_info_str, lfname);
|
|
428
|
152 }
|
|
|
153
|
|
|
154 return err == 0;
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|
|
155 }
|
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156
|
|
|
157 /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete,
|
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158 1 if another process owns it (and set OWNER (if non-null) to info),
|
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159 2 if the current process owns it,
|
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|
160 or -1 if something is wrong with the locking mechanism. */
|
|
|
161
|
|
|
162 static int
|
|
771
|
163 current_lock_owner (lock_info_type *owner, Intbyte *lfname)
|
|
428
|
164 {
|
|
442
|
165 /* Does not GC. */
|
|
|
166 int len, ret;
|
|
428
|
167 int local_owner = 0;
|
|
771
|
168 Intbyte *at, *dot;
|
|
|
169 Intbyte *lfinfo = 0;
|
|
428
|
170 int bufsize = 50;
|
|
|
171 /* Read arbitrarily-long contents of symlink. Similar code in
|
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|
172 file-symlink-p in fileio.c. */
|
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|
173 do
|
|
|
174 {
|
|
|
175 bufsize *= 2;
|
|
771
|
176 lfinfo = (Intbyte *) xrealloc (lfinfo, bufsize);
|
|
|
177 len = qxe_readlink (lfname, lfinfo, bufsize);
|
|
428
|
178 }
|
|
|
179 while (len >= bufsize);
|
|
442
|
180
|
|
428
|
181 /* If nonexistent lock file, all is well; otherwise, got strange error. */
|
|
|
182 if (len == -1)
|
|
|
183 {
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|
|
184 xfree (lfinfo);
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|
|
185 return errno == ENOENT ? 0 : -1;
|
|
|
186 }
|
|
|
187
|
|
|
188 /* Link info exists, so `len' is its length. Null terminate. */
|
|
|
189 lfinfo[len] = 0;
|
|
442
|
190
|
|
428
|
191 /* Even if the caller doesn't want the owner info, we still have to
|
|
|
192 read it to determine return value, so allocate it. */
|
|
|
193 if (!owner)
|
|
|
194 {
|
|
851
|
195 owner = (lock_info_type *) ALLOCA (sizeof (lock_info_type));
|
|
428
|
196 local_owner = 1;
|
|
|
197 }
|
|
442
|
198
|
|
428
|
199 /* Parse USER@HOST.PID. If can't parse, return -1. */
|
|
|
200 /* The USER is everything before the first @. */
|
|
771
|
201 at = qxestrchr (lfinfo, '@');
|
|
|
202 dot = qxestrrchr (lfinfo, '.');
|
|
428
|
203 if (!at || !dot) {
|
|
|
204 xfree (lfinfo);
|
|
|
205 return -1;
|
|
|
206 }
|
|
|
207 len = at - lfinfo;
|
|
771
|
208 owner->user = (Intbyte *) xmalloc (len + 1);
|
|
|
209 qxestrncpy (owner->user, lfinfo, len);
|
|
428
|
210 owner->user[len] = 0;
|
|
442
|
211
|
|
428
|
212 /* The PID is everything after the last `.'. */
|
|
771
|
213 owner->pid = atoi ((CIntbyte *) dot + 1);
|
|
428
|
214
|
|
|
215 /* The host is everything in between. */
|
|
|
216 len = dot - at - 1;
|
|
771
|
217 owner->host = (Intbyte *) xmalloc (len + 1);
|
|
|
218 qxestrncpy (owner->host, at + 1, len);
|
|
428
|
219 owner->host[len] = 0;
|
|
|
220
|
|
|
221 /* We're done looking at the link info. */
|
|
|
222 xfree (lfinfo);
|
|
442
|
223
|
|
428
|
224 /* On current host? */
|
|
442
|
225 if (STRINGP (Fsystem_name ())
|
|
771
|
226 && qxestrcmp (owner->host, XSTRING_DATA (Fsystem_name ())) == 0)
|
|
428
|
227 {
|
|
771
|
228 if (owner->pid == qxe_getpid ())
|
|
428
|
229 ret = 2; /* We own it. */
|
|
|
230 else if (owner->pid > 0
|
|
|
231 && (kill (owner->pid, 0) >= 0 || errno == EPERM))
|
|
|
232 ret = 1; /* An existing process on this machine owns it. */
|
|
|
233 /* The owner process is dead or has a strange pid (<=0), so try to
|
|
|
234 zap the lockfile. */
|
|
771
|
235 else if (qxe_unlink (lfname) < 0)
|
|
428
|
236 ret = -1;
|
|
|
237 else
|
|
|
238 ret = 0;
|
|
|
239 }
|
|
|
240 else
|
|
|
241 { /* If we wanted to support the check for stale locks on remote machines,
|
|
|
242 here's where we'd do it. */
|
|
|
243 ret = 1;
|
|
|
244 }
|
|
442
|
245
|
|
428
|
246 /* Avoid garbage. */
|
|
|
247 if (local_owner || ret <= 0)
|
|
|
248 {
|
|
|
249 FREE_LOCK_INFO (*owner);
|
|
|
250 }
|
|
|
251 return ret;
|
|
|
252 }
|
|
|
253
|
|
|
254 /* Lock the lock named LFNAME if possible.
|
|
|
255 Return 0 in that case.
|
|
|
256 Return positive if some other process owns the lock, and info about
|
|
|
257 that process in CLASHER.
|
|
|
258 Return -1 if cannot lock for any other reason. */
|
|
|
259
|
|
|
260 static int
|
|
771
|
261 lock_if_free (lock_info_type *clasher, Intbyte *lfname)
|
|
428
|
262 {
|
|
442
|
263 /* Does not GC. */
|
|
771
|
264 if (lock_file_1 ((Intbyte *) lfname, 0) == 0)
|
|
428
|
265 {
|
|
|
266 int locker;
|
|
|
267
|
|
|
268 if (errno != EEXIST)
|
|
|
269 return -1;
|
|
442
|
270
|
|
428
|
271 locker = current_lock_owner (clasher, lfname);
|
|
|
272 if (locker == 2)
|
|
|
273 {
|
|
|
274 FREE_LOCK_INFO (*clasher);
|
|
|
275 return 0; /* We ourselves locked it. */
|
|
|
276 }
|
|
|
277 else if (locker == 1)
|
|
|
278 return 1; /* Someone else has it. */
|
|
|
279
|
|
|
280 return -1; /* Something's wrong. */
|
|
|
281 }
|
|
|
282 return 0;
|
|
|
283 }
|
|
|
284
|
|
|
285 /* lock_file locks file FN,
|
|
|
286 meaning it serves notice on the world that you intend to edit that file.
|
|
|
287 This should be done only when about to modify a file-visiting
|
|
|
288 buffer previously unmodified.
|
|
|
289 Do not (normally) call this for a buffer already modified,
|
|
|
290 as either the file is already locked, or the user has already
|
|
|
291 decided to go ahead without locking.
|
|
|
292
|
|
|
293 When this returns, either the lock is locked for us,
|
|
|
294 or the user has said to go ahead without locking.
|
|
|
295
|
|
|
296 If the file is locked by someone else, this calls
|
|
|
297 ask-user-about-lock (a Lisp function) with two arguments,
|
|
|
298 the file name and info about the user who did the locking.
|
|
|
299 This function can signal an error, or return t meaning
|
|
|
300 take away the lock, or return nil meaning ignore the lock. */
|
|
|
301
|
|
|
302 void
|
|
|
303 lock_file (Lisp_Object fn)
|
|
|
304 {
|
|
442
|
305 /* This function can GC. GC checked 7-11-00 ben */
|
|
428
|
306 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
|
307 mean nasty things with pointy teeth. If you call this make sure
|
|
|
308 you protect things right. */
|
|
442
|
309 /* Somebody updated the code in this function and removed the previous
|
|
428
|
310 comment. -slb */
|
|
|
311
|
|
|
312 register Lisp_Object attack, orig_fn;
|
|
771
|
313 register Intbyte *lfname, *locker;
|
|
428
|
314 lock_info_type lock_info;
|
|
444
|
315 struct gcpro gcpro1, gcpro2, gcpro3;
|
|
|
316 Lisp_Object old_current_buffer;
|
|
428
|
317 Lisp_Object subject_buf;
|
|
|
318
|
|
444
|
319 if (inhibit_clash_detection)
|
|
|
320 return;
|
|
|
321
|
|
793
|
322 old_current_buffer = wrap_buffer (current_buffer);
|
|
446
|
323 subject_buf = Qnil;
|
|
444
|
324 GCPRO3 (fn, subject_buf, old_current_buffer);
|
|
428
|
325 orig_fn = fn;
|
|
|
326 fn = Fexpand_file_name (fn, Qnil);
|
|
|
327
|
|
|
328 /* Create the name of the lock-file for file fn */
|
|
|
329 MAKE_LOCK_NAME (lfname, fn);
|
|
|
330
|
|
|
331 /* See if this file is visited and has changed on disk since it was
|
|
|
332 visited. */
|
|
|
333 {
|
|
|
334 subject_buf = get_truename_buffer (orig_fn);
|
|
|
335 if (!NILP (subject_buf)
|
|
|
336 && NILP (Fverify_visited_file_modtime (subject_buf))
|
|
|
337 && !NILP (Ffile_exists_p (fn)))
|
|
442
|
338 call1_in_buffer (XBUFFER (subject_buf),
|
|
|
339 Qask_user_about_supersession_threat, fn);
|
|
428
|
340 }
|
|
|
341
|
|
|
342 /* Try to lock the lock. */
|
|
444
|
343 if (current_buffer != XBUFFER (old_current_buffer)
|
|
|
344 || lock_if_free (&lock_info, lfname) <= 0)
|
|
|
345 /* Return now if we have locked it, or if lock creation failed
|
|
|
346 or current buffer is killed. */
|
|
428
|
347 goto done;
|
|
|
348
|
|
|
349 /* Else consider breaking the lock */
|
|
851
|
350 locker = (Intbyte *) ALLOCA (qxestrlen (lock_info.user)
|
|
771
|
351 + qxestrlen (lock_info.host)
|
|
|
352 + LOCK_PID_MAX + 9);
|
|
|
353 qxesprintf (locker, "%s@%s (pid %d)", lock_info.user, lock_info.host,
|
|
|
354 lock_info.pid);
|
|
428
|
355 FREE_LOCK_INFO (lock_info);
|
|
442
|
356
|
|
428
|
357 attack = call2_in_buffer (BUFFERP (subject_buf) ? XBUFFER (subject_buf) :
|
|
|
358 current_buffer, Qask_user_about_lock , fn,
|
|
771
|
359 build_intstring (locker));
|
|
444
|
360 if (!NILP (attack) && current_buffer == XBUFFER (old_current_buffer))
|
|
428
|
361 /* User says take the lock */
|
|
|
362 {
|
|
|
363 lock_file_1 (lfname, 1);
|
|
|
364 goto done;
|
|
|
365 }
|
|
|
366 /* User says ignore the lock */
|
|
|
367 done:
|
|
|
368 UNGCPRO;
|
|
|
369 }
|
|
|
370
|
|
|
371 void
|
|
|
372 unlock_file (Lisp_Object fn)
|
|
|
373 {
|
|
442
|
374 /* This can GC */
|
|
771
|
375 register Intbyte *lfname;
|
|
442
|
376 struct gcpro gcpro1;
|
|
|
377
|
|
|
378 GCPRO1 (fn);
|
|
428
|
379
|
|
|
380 fn = Fexpand_file_name (fn, Qnil);
|
|
|
381
|
|
|
382 MAKE_LOCK_NAME (lfname, fn);
|
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383
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384 if (current_lock_owner (0, lfname) == 2)
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771
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385 qxe_unlink (lfname);
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442
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386
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|
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387 UNGCPRO;
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428
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388 }
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|
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389
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390 void
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|
442
|
391 unlock_all_files (void)
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428
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392 {
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393 register Lisp_Object tail;
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394
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434
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395 for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail))
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428
|
396 {
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|
442
|
397 struct buffer *b = XBUFFER (XCDR (XCAR (tail)));
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428
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398 if (STRINGP (b->file_truename) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b))
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399 unlock_file (b->file_truename);
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400 }
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|
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401 }
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|
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402
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|
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403 DEFUN ("lock-buffer", Flock_buffer, 0, 1, 0, /*
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442
|
404 Lock FILE, if current buffer is modified.
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|
|
405 FILE defaults to current buffer's visited file,
|
|
428
|
406 or else nothing is done if current buffer isn't visiting a file.
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|
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407 */
|
|
442
|
408 (file))
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|
428
|
409 {
|
|
|
410 if (NILP (file))
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411 file = current_buffer->file_truename;
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|
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412 CHECK_STRING (file);
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|
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413 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
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|
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414 && !NILP (file))
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|
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415 lock_file (file);
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|
|
416 return Qnil;
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|
|
417 }
|
|
|
418
|
|
|
419 DEFUN ("unlock-buffer", Funlock_buffer, 0, 0, 0, /*
|
|
|
420 Unlock the file visited in the current buffer,
|
|
|
421 if it should normally be locked.
|
|
|
422 */
|
|
|
423 ())
|
|
|
424 {
|
|
|
425 /* This function can GC */
|
|
|
426 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
|
427 mean nasty things with pointy teeth. If you call this make sure
|
|
|
428 you protect things right. */
|
|
|
429
|
|
|
430 if (BUF_SAVE_MODIFF (current_buffer) < BUF_MODIFF (current_buffer)
|
|
|
431 && STRINGP (current_buffer->file_truename))
|
|
|
432 unlock_file (current_buffer->file_truename);
|
|
|
433 return Qnil;
|
|
|
434 }
|
|
|
435
|
|
|
436 /* Unlock the file visited in buffer BUFFER. */
|
|
|
437
|
|
|
438
|
|
|
439 void
|
|
|
440 unlock_buffer (struct buffer *buffer)
|
|
|
441 {
|
|
|
442 /* This function can GC */
|
|
|
443 /* dmoore - and can destroy current_buffer and all sorts of other
|
|
|
444 mean nasty things with pointy teeth. If you call this make sure
|
|
|
445 you protect things right. */
|
|
|
446 if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer)
|
|
|
447 && STRINGP (buffer->file_truename))
|
|
|
448 unlock_file (buffer->file_truename);
|
|
|
449 }
|
|
|
450
|
|
|
451 DEFUN ("file-locked-p", Ffile_locked_p, 0, 1, 0, /*
|
|
442
|
452 Return nil if the FILENAME is not locked,
|
|
428
|
453 t if it is locked by you, else a string of the name of the locker.
|
|
|
454 */
|
|
442
|
455 (filename))
|
|
428
|
456 {
|
|
|
457 Lisp_Object ret;
|
|
771
|
458 register Intbyte *lfname;
|
|
428
|
459 int owner;
|
|
|
460 lock_info_type locker;
|
|
442
|
461 struct gcpro gcpro1;
|
|
|
462
|
|
|
463 GCPRO1 (filename);
|
|
428
|
464
|
|
|
465 filename = Fexpand_file_name (filename, Qnil);
|
|
|
466
|
|
|
467 MAKE_LOCK_NAME (lfname, filename);
|
|
|
468
|
|
|
469 owner = current_lock_owner (&locker, lfname);
|
|
|
470 if (owner <= 0)
|
|
|
471 ret = Qnil;
|
|
|
472 else if (owner == 2)
|
|
|
473 ret = Qt;
|
|
|
474 else
|
|
771
|
475 ret = build_intstring (locker.user);
|
|
428
|
476
|
|
|
477 if (owner > 0)
|
|
|
478 FREE_LOCK_INFO (locker);
|
|
|
479
|
|
442
|
480 UNGCPRO;
|
|
|
481
|
|
428
|
482 return ret;
|
|
|
483 }
|
|
|
484
|
|
|
485
|
|
|
486 /* Initialization functions. */
|
|
|
487
|
|
|
488 void
|
|
|
489 syms_of_filelock (void)
|
|
|
490 {
|
|
|
491 /* This function can GC */
|
|
|
492 DEFSUBR (Funlock_buffer);
|
|
|
493 DEFSUBR (Flock_buffer);
|
|
|
494 DEFSUBR (Ffile_locked_p);
|
|
|
495
|
|
563
|
496 DEFSYMBOL (Qask_user_about_supersession_threat);
|
|
|
497 DEFSYMBOL (Qask_user_about_lock);
|
|
428
|
498 }
|
|
|
499
|
|
444
|
500 void
|
|
|
501 vars_of_filelock (void)
|
|
|
502 {
|
|
|
503 DEFVAR_BOOL ("inhibit-clash-detection", &inhibit_clash_detection /*
|
|
|
504 Non-nil inhibits creation of lock file to detect clash.
|
|
|
505 */);
|
|
|
506 inhibit_clash_detection = 0;
|
|
|
507 }
|
|
428
|
508
|
|
|
509 #endif /* CLASH_DETECTION */
|
