Commit | Line | Data |
---|---|---|
b97771fc | 1 | /* Lock files for editing. |
acaf905b | 2 | Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2012 |
8cabe764 | 3 | Free Software Foundation, Inc. |
8489eb67 RS |
4 | |
5 | This file is part of GNU Emacs. | |
6 | ||
9ec0b715 | 7 | GNU Emacs is free software: you can redistribute it and/or modify |
8489eb67 | 8 | it under the terms of the GNU General Public License as published by |
9ec0b715 GM |
9 | the Free Software Foundation, either version 3 of the License, or |
10 | (at your option) any later version. | |
8489eb67 RS |
11 | |
12 | GNU Emacs 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 | |
9ec0b715 | 18 | along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */ |
8489eb67 RS |
19 | |
20 | ||
68c45bf0 | 21 | #include <config.h> |
8489eb67 RS |
22 | #include <sys/types.h> |
23 | #include <sys/stat.h> | |
dfcf069d | 24 | #include <signal.h> |
2decc5a9 | 25 | #include <stdio.h> |
bfb61299 | 26 | |
5b9c0a1d | 27 | #ifdef HAVE_PWD_H |
8489eb67 | 28 | #include <pwd.h> |
5b9c0a1d | 29 | #endif |
bfb61299 | 30 | |
8489eb67 | 31 | #include <sys/file.h> |
8489eb67 | 32 | #include <fcntl.h> |
dfcf069d | 33 | #include <unistd.h> |
dfcf069d | 34 | |
f805a125 | 35 | #ifdef __FreeBSD__ |
f805a125 KH |
36 | #include <sys/sysctl.h> |
37 | #endif /* __FreeBSD__ */ | |
38 | ||
e5ef3cdf | 39 | #include <errno.h> |
e5ef3cdf | 40 | |
8489eb67 | 41 | #include "lisp.h" |
d2f6dae8 | 42 | #include "character.h" |
e5560ff7 | 43 | #include "buffer.h" |
f4a4528d | 44 | #include "coding.h" |
9177d978 | 45 | #include "systime.h" |
8489eb67 | 46 | |
8489eb67 | 47 | #ifdef CLASH_DETECTION |
e788eecc | 48 | |
c6d09b8d | 49 | #ifdef HAVE_UTMP_H |
e788eecc | 50 | #include <utmp.h> |
c6d09b8d | 51 | #endif |
77e544a4 | 52 | |
a48de9b2 PE |
53 | /* A file whose last-modified time is just after the most recent boot. |
54 | Define this to be NULL to disable checking for this file. */ | |
55 | #ifndef BOOT_TIME_FILE | |
56 | #define BOOT_TIME_FILE "/var/run/random-seed" | |
57 | #endif | |
58 | ||
77e544a4 RS |
59 | #ifndef WTMP_FILE |
60 | #define WTMP_FILE "/var/log/wtmp" | |
61 | #endif | |
177c0ea7 | 62 | |
8dbbc384 RS |
63 | /* The strategy: to lock a file FN, create a symlink .#FN in FN's |
64 | directory, with link data `user@host.pid'. This avoids a single | |
65 | mount (== failure) point for lock files. | |
66 | ||
67 | When the host in the lock data is the current host, we can check if | |
68 | the pid is valid with kill. | |
177c0ea7 | 69 | |
8dbbc384 RS |
70 | Otherwise, we could look at a separate file that maps hostnames to |
71 | reboot times to see if the remote pid can possibly be valid, since we | |
72 | don't want Emacs to have to communicate via pipes or sockets or | |
73 | whatever to other processes, either locally or remotely; rms says | |
74 | that's too unreliable. Hence the separate file, which could | |
75 | theoretically be updated by daemons running separately -- but this | |
76 | whole idea is unimplemented; in practice, at least in our | |
1c4f857c | 77 | environment, it seems such stale locks arise fairly infrequently, and |
8dbbc384 RS |
78 | Emacs' standard methods of dealing with clashes suffice. |
79 | ||
80 | We use symlinks instead of normal files because (1) they can be | |
81 | stored more efficiently on the filesystem, since the kernel knows | |
82 | they will be small, and (2) all the info about the lock can be read | |
83 | in a single system call (readlink). Although we could use regular | |
1c4f857c | 84 | files to be useful on old systems lacking symlinks, nowadays |
8dbbc384 RS |
85 | virtually all such systems are probably single-user anyway, so it |
86 | didn't seem worth the complication. | |
177c0ea7 | 87 | |
8dbbc384 RS |
88 | Similarly, we don't worry about a possible 14-character limit on |
89 | file names, because those are all the same systems that don't have | |
90 | symlinks. | |
177c0ea7 | 91 | |
8dbbc384 RS |
92 | This is compatible with the locking scheme used by Interleaf (which |
93 | has contributed this implementation for Emacs), and was designed by | |
94 | Ethan Jacobson, Kimbo Mundy, and others. | |
177c0ea7 | 95 | |
8dbbc384 | 96 | --karl@cs.umb.edu/karl@hq.ileaf.com. */ |
8489eb67 | 97 | |
8dbbc384 | 98 | \f |
15e88d21 RS |
99 | /* Return the time of the last system boot. */ |
100 | ||
101 | static time_t boot_time; | |
f75d7a91 | 102 | static bool boot_time_initialized; |
15e88d21 | 103 | |
2f2500ef | 104 | #ifdef BOOT_TIME |
f75d7a91 | 105 | static void get_boot_time_1 (const char *, bool); |
2f2500ef DL |
106 | #endif |
107 | ||
15e88d21 | 108 | static time_t |
971de7fb | 109 | get_boot_time (void) |
15e88d21 | 110 | { |
9d2818d6 | 111 | #if defined (BOOT_TIME) |
9177d978 | 112 | int counter; |
2decc5a9 | 113 | #endif |
15e88d21 | 114 | |
b97771fc | 115 | if (boot_time_initialized) |
15e88d21 | 116 | return boot_time; |
b97771fc | 117 | boot_time_initialized = 1; |
15e88d21 | 118 | |
f805a125 KH |
119 | #if defined (CTL_KERN) && defined (KERN_BOOTTIME) |
120 | { | |
121 | int mib[2]; | |
122 | size_t size; | |
123 | struct timeval boottime_val; | |
124 | ||
125 | mib[0] = CTL_KERN; | |
126 | mib[1] = KERN_BOOTTIME; | |
127 | size = sizeof (boottime_val); | |
128 | ||
129 | if (sysctl (mib, 2, &boottime_val, &size, NULL, 0) >= 0) | |
130 | { | |
131 | boot_time = boottime_val.tv_sec; | |
132 | return boot_time; | |
133 | } | |
134 | } | |
135 | #endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */ | |
9177d978 | 136 | |
a48de9b2 PE |
137 | if (BOOT_TIME_FILE) |
138 | { | |
139 | struct stat st; | |
140 | if (stat (BOOT_TIME_FILE, &st) == 0) | |
141 | { | |
142 | boot_time = st.st_mtime; | |
143 | return boot_time; | |
144 | } | |
145 | } | |
146 | ||
9d2818d6 | 147 | #if defined (BOOT_TIME) |
b97771fc RS |
148 | #ifndef CANNOT_DUMP |
149 | /* The utmp routines maintain static state. | |
150 | Don't touch that state unless we are initialized, | |
151 | since it might not survive dumping. */ | |
152 | if (! initialized) | |
153 | return boot_time; | |
154 | #endif /* not CANNOT_DUMP */ | |
155 | ||
156 | /* Try to get boot time from utmp before wtmp, | |
157 | since utmp is typically much smaller than wtmp. | |
158 | Passing a null pointer causes get_boot_time_1 | |
159 | to inspect the default file, namely utmp. */ | |
160 | get_boot_time_1 ((char *) 0, 0); | |
161 | if (boot_time) | |
162 | return boot_time; | |
163 | ||
9177d978 | 164 | /* Try to get boot time from the current wtmp file. */ |
b97771fc | 165 | get_boot_time_1 (WTMP_FILE, 1); |
9177d978 RS |
166 | |
167 | /* If we did not find a boot time in wtmp, look at wtmp, and so on. */ | |
b97771fc | 168 | for (counter = 0; counter < 20 && ! boot_time; counter++) |
9177d978 | 169 | { |
882f0d81 | 170 | char cmd_string[sizeof WTMP_FILE ".19.gz"]; |
9177d978 | 171 | Lisp_Object tempname, filename; |
f75d7a91 | 172 | bool delete_flag = 0; |
9177d978 RS |
173 | |
174 | filename = Qnil; | |
175 | ||
a8290ec3 DA |
176 | tempname = make_formatted_string |
177 | (cmd_string, "%s.%d", WTMP_FILE, counter); | |
29a2adb0 | 178 | if (! NILP (Ffile_exists_p (tempname))) |
9177d978 RS |
179 | filename = tempname; |
180 | else | |
181 | { | |
a8290ec3 DA |
182 | tempname = make_formatted_string (cmd_string, "%s.%d.gz", |
183 | WTMP_FILE, counter); | |
9177d978 RS |
184 | if (! NILP (Ffile_exists_p (tempname))) |
185 | { | |
186 | Lisp_Object args[6]; | |
f1d367aa GM |
187 | |
188 | /* The utmp functions on mescaline.gnu.org accept only | |
189 | file names up to 8 characters long. Choose a 2 | |
190 | character long prefix, and call make_temp_file with | |
191 | second arg non-zero, so that it will add not more | |
192 | than 6 characters to the prefix. */ | |
882f0d81 | 193 | filename = Fexpand_file_name (build_string ("wt"), |
5f8d6a10 | 194 | Vtemporary_file_directory); |
882f0d81 PE |
195 | filename = make_temp_name (filename, 1); |
196 | args[0] = build_string ("gzip"); | |
9177d978 | 197 | args[1] = Qnil; |
882f0d81 | 198 | args[2] = list2 (QCfile, filename); |
9177d978 | 199 | args[3] = Qnil; |
882f0d81 PE |
200 | args[4] = build_string ("-cd"); |
201 | args[5] = tempname; | |
9177d978 | 202 | Fcall_process (6, args); |
9177d978 RS |
203 | delete_flag = 1; |
204 | } | |
205 | } | |
206 | ||
207 | if (! NILP (filename)) | |
208 | { | |
42a5b22f | 209 | get_boot_time_1 (SSDATA (filename), 1); |
9177d978 | 210 | if (delete_flag) |
42a5b22f | 211 | unlink (SSDATA (filename)); |
9177d978 RS |
212 | } |
213 | } | |
214 | ||
215 | return boot_time; | |
216 | #else | |
217 | return 0; | |
218 | #endif | |
219 | } | |
220 | ||
e9f22ced | 221 | #ifdef BOOT_TIME |
9177d978 RS |
222 | /* Try to get the boot time from wtmp file FILENAME. |
223 | This succeeds if that file contains a reboot record. | |
9177d978 | 224 | |
b97771fc RS |
225 | If FILENAME is zero, use the same file as before; |
226 | if no FILENAME has ever been specified, this is the utmp file. | |
f75d7a91 | 227 | Use the newest reboot record if NEWEST, |
b97771fc RS |
228 | the first reboot record otherwise. |
229 | Ignore all reboot records on or before BOOT_TIME. | |
230 | Success is indicated by setting BOOT_TIME to a larger value. */ | |
231 | ||
2f2500ef | 232 | void |
f75d7a91 | 233 | get_boot_time_1 (const char *filename, bool newest) |
9177d978 RS |
234 | { |
235 | struct utmp ut, *utp; | |
77e544a4 RS |
236 | int desc; |
237 | ||
b97771fc RS |
238 | if (filename) |
239 | { | |
240 | /* On some versions of IRIX, opening a nonexistent file name | |
241 | is likely to crash in the utmp routines. */ | |
68c45bf0 | 242 | desc = emacs_open (filename, O_RDONLY, 0); |
b97771fc RS |
243 | if (desc < 0) |
244 | return; | |
245 | ||
68c45bf0 | 246 | emacs_close (desc); |
b97771fc RS |
247 | |
248 | utmpname (filename); | |
249 | } | |
9177d978 | 250 | |
c321b190 | 251 | setutent (); |
b97771fc | 252 | |
c321b190 RS |
253 | while (1) |
254 | { | |
255 | /* Find the next reboot record. */ | |
256 | ut.ut_type = BOOT_TIME; | |
257 | utp = getutid (&ut); | |
258 | if (! utp) | |
259 | break; | |
260 | /* Compare reboot times and use the newest one. */ | |
261 | if (utp->ut_time > boot_time) | |
b97771fc RS |
262 | { |
263 | boot_time = utp->ut_time; | |
264 | if (! newest) | |
265 | break; | |
266 | } | |
c321b190 RS |
267 | /* Advance on element in the file |
268 | so that getutid won't repeat the same one. */ | |
269 | utp = getutent (); | |
270 | if (! utp) | |
271 | break; | |
272 | } | |
15e88d21 | 273 | endutent (); |
15e88d21 | 274 | } |
e9f22ced | 275 | #endif /* BOOT_TIME */ |
15e88d21 | 276 | \f |
8dbbc384 | 277 | /* Here is the structure that stores information about a lock. */ |
32676c08 | 278 | |
8dbbc384 RS |
279 | typedef struct |
280 | { | |
281 | char *user; | |
282 | char *host; | |
882f0d81 | 283 | pid_t pid; |
15e88d21 | 284 | time_t boot_time; |
8dbbc384 | 285 | } lock_info_type; |
32676c08 | 286 | |
8dbbc384 RS |
287 | /* Free the two dynamically-allocated pieces in PTR. */ |
288 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 289 | |
e31fbc7a | 290 | |
8dbbc384 | 291 | /* Write the name of the lock file for FN into LFNAME. Length will be |
c1355e1f GM |
292 | that of FN plus two more for the leading `.#' plus 1 for the |
293 | trailing period plus one for the digit after it plus one for the | |
294 | null. */ | |
7b92975f | 295 | #define MAKE_LOCK_NAME(lock, file) \ |
38182d90 | 296 | (lock = alloca (SBYTES (file) + 2 + 1 + 1 + 1), \ |
8dbbc384 | 297 | fill_in_lock_file_name (lock, (file))) |
e31fbc7a | 298 | |
8dbbc384 | 299 | static void |
971de7fb | 300 | fill_in_lock_file_name (register char *lockfile, register Lisp_Object fn) |
e31fbc7a | 301 | { |
c293e30c | 302 | ptrdiff_t length = SBYTES (fn); |
8dbbc384 | 303 | register char *p; |
c1355e1f GM |
304 | struct stat st; |
305 | int count = 0; | |
8dbbc384 | 306 | |
42a5b22f | 307 | strcpy (lockfile, SSDATA (fn)); |
8dbbc384 RS |
308 | |
309 | /* Shift the nondirectory part of the file name (including the null) | |
310 | right two characters. Here is one of the places where we'd have to | |
311 | do something to support 14-character-max file names. */ | |
c293e30c | 312 | for (p = lockfile + length; p != lockfile && *p != '/'; p--) |
8dbbc384 | 313 | p[2] = *p; |
177c0ea7 | 314 | |
8dbbc384 RS |
315 | /* Insert the `.#'. */ |
316 | p[1] = '.'; | |
317 | p[2] = '#'; | |
c1355e1f | 318 | |
c293e30c | 319 | p = p + length + 2; |
c1355e1f GM |
320 | |
321 | while (lstat (lockfile, &st) == 0 && !S_ISLNK (st.st_mode)) | |
322 | { | |
323 | if (count > 9) | |
324 | { | |
325 | *p = '\0'; | |
326 | return; | |
327 | } | |
328 | sprintf (p, ".%d", count++); | |
329 | } | |
8dbbc384 | 330 | } |
e31fbc7a | 331 | |
8dbbc384 | 332 | /* Lock the lock file named LFNAME. |
f75d7a91 PE |
333 | If FORCE, do so even if it is already locked. |
334 | Return true if successful. */ | |
e31fbc7a | 335 | |
f75d7a91 PE |
336 | static bool |
337 | lock_file_1 (char *lfname, bool force) | |
8dbbc384 | 338 | { |
98c6f1e3 | 339 | int err; |
b5cd1905 PE |
340 | int symlink_errno; |
341 | USE_SAFE_ALLOCA; | |
662c2ef2 | 342 | |
4ba93ac0 | 343 | /* Call this first because it can GC. */ |
98c6f1e3 PE |
344 | printmax_t boot = get_boot_time (); |
345 | ||
346 | Lisp_Object luser_name = Fuser_login_name (Qnil); | |
347 | char const *user_name = STRINGP (luser_name) ? SSDATA (luser_name) : ""; | |
348 | Lisp_Object lhost_name = Fsystem_name (); | |
349 | char const *host_name = STRINGP (lhost_name) ? SSDATA (lhost_name) : ""; | |
350 | ptrdiff_t lock_info_size = (strlen (user_name) + strlen (host_name) | |
351 | + 2 * INT_STRLEN_BOUND (printmax_t) | |
352 | + sizeof "@.:"); | |
353 | char *lock_info_str = SAFE_ALLOCA (lock_info_size); | |
354 | printmax_t pid = getpid (); | |
8dbbc384 | 355 | |
b5cd1905 PE |
356 | esprintf (lock_info_str, boot ? "%s@%s.%"pMd":%"pMd : "%s@%s.%"pMd, |
357 | user_name, host_name, pid, boot); | |
8dbbc384 RS |
358 | |
359 | err = symlink (lock_info_str, lfname); | |
360 | if (errno == EEXIST && force) | |
e31fbc7a | 361 | { |
8dbbc384 RS |
362 | unlink (lfname); |
363 | err = symlink (lock_info_str, lfname); | |
e31fbc7a | 364 | } |
e31fbc7a | 365 | |
b5cd1905 PE |
366 | symlink_errno = errno; |
367 | SAFE_FREE (); | |
368 | errno = symlink_errno; | |
8dbbc384 RS |
369 | return err == 0; |
370 | } | |
e31fbc7a | 371 | |
f75d7a91 | 372 | /* Return true if times A and B are no more than one second apart. */ |
32676c08 | 373 | |
f75d7a91 | 374 | static bool |
971de7fb | 375 | within_one_second (time_t a, time_t b) |
9177d978 RS |
376 | { |
377 | return (a - b >= -1 && a - b <= 1); | |
378 | } | |
8dbbc384 RS |
379 | \f |
380 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, | |
381 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
382 | 2 if the current process owns it, | |
383 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 384 | |
8dbbc384 | 385 | static int |
971de7fb | 386 | current_lock_owner (lock_info_type *owner, char *lfname) |
32676c08 | 387 | { |
d1fdcab7 | 388 | int ret; |
882f0d81 PE |
389 | ptrdiff_t len; |
390 | lock_info_type local_owner; | |
391 | intmax_t n; | |
15e88d21 | 392 | char *at, *dot, *colon; |
d1fdcab7 PE |
393 | char readlink_buf[READLINK_BUFSIZE]; |
394 | char *lfinfo = emacs_readlink (lfname, readlink_buf); | |
177c0ea7 | 395 | |
8dbbc384 | 396 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ |
d1fdcab7 PE |
397 | if (!lfinfo) |
398 | return errno == ENOENT ? 0 : -1; | |
177c0ea7 | 399 | |
8dbbc384 | 400 | /* Even if the caller doesn't want the owner info, we still have to |
882f0d81 | 401 | read it to determine return value. */ |
8dbbc384 | 402 | if (!owner) |
882f0d81 | 403 | owner = &local_owner; |
177c0ea7 | 404 | |
15e88d21 | 405 | /* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */ |
50624218 | 406 | /* The USER is everything before the last @. */ |
8966b757 AS |
407 | at = strrchr (lfinfo, '@'); |
408 | dot = strrchr (lfinfo, '.'); | |
15e88d21 RS |
409 | if (!at || !dot) |
410 | { | |
d1fdcab7 PE |
411 | if (lfinfo != readlink_buf) |
412 | xfree (lfinfo); | |
15e88d21 RS |
413 | return -1; |
414 | } | |
8dbbc384 | 415 | len = at - lfinfo; |
23f86fce | 416 | owner->user = xmalloc (len + 1); |
882f0d81 | 417 | memcpy (owner->user, lfinfo, len); |
8dbbc384 | 418 | owner->user[len] = 0; |
177c0ea7 | 419 | |
15e88d21 | 420 | /* The PID is everything from the last `.' to the `:'. */ |
882f0d81 PE |
421 | errno = 0; |
422 | n = strtoimax (dot + 1, NULL, 10); | |
423 | owner->pid = | |
424 | ((0 <= n && n <= TYPE_MAXIMUM (pid_t) | |
425 | && (TYPE_MAXIMUM (pid_t) < INTMAX_MAX || errno != ERANGE)) | |
426 | ? n : 0); | |
427 | ||
428 | colon = strchr (dot + 1, ':'); | |
15e88d21 | 429 | /* After the `:', if there is one, comes the boot time. */ |
882f0d81 PE |
430 | n = 0; |
431 | if (colon) | |
432 | { | |
433 | errno = 0; | |
434 | n = strtoimax (colon + 1, NULL, 10); | |
435 | } | |
436 | owner->boot_time = | |
437 | ((0 <= n && n <= TYPE_MAXIMUM (time_t) | |
438 | && (TYPE_MAXIMUM (time_t) < INTMAX_MAX || errno != ERANGE)) | |
439 | ? n : 0); | |
32676c08 | 440 | |
8dbbc384 RS |
441 | /* The host is everything in between. */ |
442 | len = dot - at - 1; | |
23f86fce | 443 | owner->host = xmalloc (len + 1); |
882f0d81 | 444 | memcpy (owner->host, at + 1, len); |
8dbbc384 | 445 | owner->host[len] = 0; |
32676c08 | 446 | |
8dbbc384 | 447 | /* We're done looking at the link info. */ |
d1fdcab7 PE |
448 | if (lfinfo != readlink_buf) |
449 | xfree (lfinfo); | |
177c0ea7 | 450 | |
8dbbc384 | 451 | /* On current host? */ |
662c2ef2 | 452 | if (STRINGP (Fsystem_name ()) |
42a5b22f | 453 | && strcmp (owner->host, SSDATA (Fsystem_name ())) == 0) |
32676c08 | 454 | { |
8dbbc384 RS |
455 | if (owner->pid == getpid ()) |
456 | ret = 2; /* We own it. */ | |
72dcef0e | 457 | else if (owner->pid > 0 |
15e88d21 RS |
458 | && (kill (owner->pid, 0) >= 0 || errno == EPERM) |
459 | && (owner->boot_time == 0 | |
9177d978 | 460 | || within_one_second (owner->boot_time, get_boot_time ()))) |
8dbbc384 | 461 | ret = 1; /* An existing process on this machine owns it. */ |
8dbbc384 RS |
462 | /* The owner process is dead or has a strange pid (<=0), so try to |
463 | zap the lockfile. */ | |
72dcef0e | 464 | else if (unlink (lfname) < 0) |
8dbbc384 | 465 | ret = -1; |
72dcef0e RS |
466 | else |
467 | ret = 0; | |
32676c08 | 468 | } |
8dbbc384 RS |
469 | else |
470 | { /* If we wanted to support the check for stale locks on remote machines, | |
471 | here's where we'd do it. */ | |
472 | ret = 1; | |
473 | } | |
177c0ea7 | 474 | |
8dbbc384 | 475 | /* Avoid garbage. */ |
882f0d81 | 476 | if (owner == &local_owner || ret <= 0) |
8dbbc384 RS |
477 | { |
478 | FREE_LOCK_INFO (*owner); | |
479 | } | |
480 | return ret; | |
32676c08 JB |
481 | } |
482 | ||
8dbbc384 RS |
483 | \f |
484 | /* Lock the lock named LFNAME if possible. | |
485 | Return 0 in that case. | |
486 | Return positive if some other process owns the lock, and info about | |
487 | that process in CLASHER. | |
488 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 489 | |
8dbbc384 | 490 | static int |
971de7fb | 491 | lock_if_free (lock_info_type *clasher, register char *lfname) |
8dbbc384 | 492 | { |
f75d7a91 | 493 | while (! lock_file_1 (lfname, 0)) |
8dbbc384 RS |
494 | { |
495 | int locker; | |
e0e0205b | 496 | |
8dbbc384 RS |
497 | if (errno != EEXIST) |
498 | return -1; | |
177c0ea7 | 499 | |
8dbbc384 RS |
500 | locker = current_lock_owner (clasher, lfname); |
501 | if (locker == 2) | |
502 | { | |
503 | FREE_LOCK_INFO (*clasher); | |
504 | return 0; /* We ourselves locked it. */ | |
505 | } | |
506 | else if (locker == 1) | |
507 | return 1; /* Someone else has it. */ | |
5df0b2fa | 508 | else if (locker == -1) |
ae1ef097 | 509 | return -1; /* current_lock_owner returned strange error. */ |
8dbbc384 | 510 | |
cfc01fa7 | 511 | /* We deleted a stale lock; try again to lock the file. */ |
8dbbc384 RS |
512 | } |
513 | return 0; | |
8489eb67 RS |
514 | } |
515 | ||
8dbbc384 | 516 | /* lock_file locks file FN, |
8489eb67 RS |
517 | meaning it serves notice on the world that you intend to edit that file. |
518 | This should be done only when about to modify a file-visiting | |
519 | buffer previously unmodified. | |
8dbbc384 | 520 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
521 | as either the file is already locked, or the user has already |
522 | decided to go ahead without locking. | |
523 | ||
8dbbc384 | 524 | When this returns, either the lock is locked for us, |
8489eb67 RS |
525 | or the user has said to go ahead without locking. |
526 | ||
8dbbc384 | 527 | If the file is locked by someone else, this calls |
8489eb67 | 528 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 529 | the file name and info about the user who did the locking. |
8489eb67 RS |
530 | This function can signal an error, or return t meaning |
531 | take away the lock, or return nil meaning ignore the lock. */ | |
532 | ||
8489eb67 | 533 | void |
971de7fb | 534 | lock_file (Lisp_Object fn) |
8489eb67 | 535 | { |
f4a4528d | 536 | register Lisp_Object attack, orig_fn, encoded_fn; |
8dbbc384 | 537 | register char *lfname, *locker; |
b5cd1905 | 538 | ptrdiff_t locker_size; |
8dbbc384 | 539 | lock_info_type lock_info; |
a81d11a3 | 540 | printmax_t pid; |
3edc33a4 | 541 | struct gcpro gcpro1; |
b5cd1905 | 542 | USE_SAFE_ALLOCA; |
8489eb67 | 543 | |
836d29b3 DA |
544 | /* Don't do locking if the user has opted out. */ |
545 | if (! create_lockfiles) | |
546 | return; | |
547 | ||
33bae690 RS |
548 | /* Don't do locking while dumping Emacs. |
549 | Uncompressing wtmp files uses call-process, which does not work | |
550 | in an uninitialized Emacs. */ | |
551 | if (! NILP (Vpurify_flag)) | |
552 | return; | |
553 | ||
5383bc6d | 554 | orig_fn = fn; |
8af8a9ca | 555 | GCPRO1 (fn); |
1e89de84 | 556 | fn = Fexpand_file_name (fn, Qnil); |
f4a4528d | 557 | encoded_fn = ENCODE_FILE (fn); |
1e89de84 | 558 | |
8dbbc384 | 559 | /* Create the name of the lock-file for file fn */ |
f4a4528d | 560 | MAKE_LOCK_NAME (lfname, encoded_fn); |
8489eb67 | 561 | |
32676c08 JB |
562 | /* See if this file is visited and has changed on disk since it was |
563 | visited. */ | |
8489eb67 | 564 | { |
a57bc488 | 565 | register Lisp_Object subject_buf; |
3036594f | 566 | |
5383bc6d | 567 | subject_buf = get_truename_buffer (orig_fn); |
3036594f | 568 | |
265a9e55 JB |
569 | if (!NILP (subject_buf) |
570 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
571 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 | 572 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
3036594f | 573 | |
8489eb67 | 574 | } |
8af8a9ca | 575 | UNGCPRO; |
8489eb67 RS |
576 | |
577 | /* Try to lock the lock. */ | |
8dbbc384 RS |
578 | if (lock_if_free (&lock_info, lfname) <= 0) |
579 | /* Return now if we have locked it, or if lock creation failed */ | |
8489eb67 RS |
580 | return; |
581 | ||
582 | /* Else consider breaking the lock */ | |
b5cd1905 PE |
583 | locker_size = (strlen (lock_info.user) + strlen (lock_info.host) |
584 | + INT_STRLEN_BOUND (printmax_t) | |
585 | + sizeof "@ (pid )"); | |
98c6f1e3 | 586 | locker = SAFE_ALLOCA (locker_size); |
882f0d81 | 587 | pid = lock_info.pid; |
b5cd1905 PE |
588 | esprintf (locker, "%s@%s (pid %"pMd")", |
589 | lock_info.user, lock_info.host, pid); | |
8dbbc384 | 590 | FREE_LOCK_INFO (lock_info); |
177c0ea7 | 591 | |
8dbbc384 | 592 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); |
b5cd1905 | 593 | SAFE_FREE (); |
265a9e55 | 594 | if (!NILP (attack)) |
8489eb67 RS |
595 | /* User says take the lock */ |
596 | { | |
8dbbc384 | 597 | lock_file_1 (lfname, 1); |
8489eb67 RS |
598 | return; |
599 | } | |
600 | /* User says ignore the lock */ | |
601 | } | |
602 | ||
8489eb67 | 603 | void |
971de7fb | 604 | unlock_file (register Lisp_Object fn) |
8489eb67 RS |
605 | { |
606 | register char *lfname; | |
607 | ||
1e89de84 | 608 | fn = Fexpand_file_name (fn, Qnil); |
88eace34 | 609 | fn = ENCODE_FILE (fn); |
1e89de84 | 610 | |
7b92975f | 611 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 612 | |
8dbbc384 | 613 | if (current_lock_owner (0, lfname) == 2) |
8489eb67 | 614 | unlink (lfname); |
8489eb67 RS |
615 | } |
616 | ||
617 | void | |
971de7fb | 618 | unlock_all_files (void) |
8489eb67 RS |
619 | { |
620 | register Lisp_Object tail; | |
621 | register struct buffer *b; | |
622 | ||
8e50cc2d | 623 | for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail)) |
8489eb67 | 624 | { |
03699b14 | 625 | b = XBUFFER (XCDR (XCAR (tail))); |
4b4deea2 | 626 | if (STRINGP (BVAR (b, file_truename)) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) |
1c343051 | 627 | { |
5e617bc2 | 628 | unlock_file (BVAR (b, file_truename)); |
1c343051 | 629 | } |
8489eb67 RS |
630 | } |
631 | } | |
8489eb67 RS |
632 | \f |
633 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
335c5470 PJ |
634 | 0, 1, 0, |
635 | doc: /* Lock FILE, if current buffer is modified. | |
636 | FILE defaults to current buffer's visited file, | |
637 | or else nothing is done if current buffer isn't visiting a file. */) | |
5842a27b | 638 | (Lisp_Object file) |
8489eb67 | 639 | { |
e9319ef2 | 640 | if (NILP (file)) |
4b4deea2 | 641 | file = BVAR (current_buffer, file_truename); |
8489eb67 | 642 | else |
b7826503 | 643 | CHECK_STRING (file); |
6a140159 | 644 | if (SAVE_MODIFF < MODIFF |
e9319ef2 EN |
645 | && !NILP (file)) |
646 | lock_file (file); | |
177c0ea7 | 647 | return Qnil; |
8489eb67 RS |
648 | } |
649 | ||
a7ca3326 | 650 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, |
335c5470 | 651 | 0, 0, 0, |
3bfb8921 RS |
652 | doc: /* Unlock the file visited in the current buffer. |
653 | If the buffer is not modified, this does nothing because the file | |
654 | should not be locked in that case. */) | |
5842a27b | 655 | (void) |
8489eb67 | 656 | { |
6a140159 | 657 | if (SAVE_MODIFF < MODIFF |
4b4deea2 TT |
658 | && STRINGP (BVAR (current_buffer, file_truename))) |
659 | unlock_file (BVAR (current_buffer, file_truename)); | |
8489eb67 RS |
660 | return Qnil; |
661 | } | |
662 | ||
8489eb67 RS |
663 | /* Unlock the file visited in buffer BUFFER. */ |
664 | ||
d07e0802 | 665 | void |
971de7fb | 666 | unlock_buffer (struct buffer *buffer) |
8489eb67 | 667 | { |
6a140159 | 668 | if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer) |
4b4deea2 TT |
669 | && STRINGP (BVAR (buffer, file_truename))) |
670 | unlock_file (BVAR (buffer, file_truename)); | |
8489eb67 RS |
671 | } |
672 | ||
8105cbf7 | 673 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 1, 1, 0, |
3bfb8921 RS |
674 | doc: /* Return a value indicating whether FILENAME is locked. |
675 | The value is nil if the FILENAME is not locked, | |
676 | t if it is locked by you, else a string saying which user has locked it. */) | |
5842a27b | 677 | (Lisp_Object filename) |
8489eb67 | 678 | { |
8dbbc384 | 679 | Lisp_Object ret; |
8489eb67 RS |
680 | register char *lfname; |
681 | int owner; | |
8dbbc384 | 682 | lock_info_type locker; |
8489eb67 | 683 | |
e9319ef2 | 684 | filename = Fexpand_file_name (filename, Qnil); |
8489eb67 | 685 | |
e9319ef2 | 686 | MAKE_LOCK_NAME (lfname, filename); |
8489eb67 | 687 | |
8dbbc384 | 688 | owner = current_lock_owner (&locker, lfname); |
8489eb67 | 689 | if (owner <= 0) |
8dbbc384 RS |
690 | ret = Qnil; |
691 | else if (owner == 2) | |
692 | ret = Qt; | |
693 | else | |
694 | ret = build_string (locker.user); | |
695 | ||
696 | if (owner > 0) | |
697 | FREE_LOCK_INFO (locker); | |
698 | ||
699 | return ret; | |
8489eb67 | 700 | } |
a3fd58aa | 701 | |
ffe75e6b EZ |
702 | #endif /* CLASH_DETECTION */ |
703 | ||
dfcf069d | 704 | void |
971de7fb | 705 | syms_of_filelock (void) |
8489eb67 | 706 | { |
29208e82 | 707 | DEFVAR_LISP ("temporary-file-directory", Vtemporary_file_directory, |
335c5470 | 708 | doc: /* The directory for writing temporary files. */); |
5f8d6a10 RS |
709 | Vtemporary_file_directory = Qnil; |
710 | ||
836d29b3 DA |
711 | DEFVAR_BOOL ("create-lockfiles", create_lockfiles, |
712 | doc: /* Non-nil means use lockfiles to avoid editing collisions. */); | |
713 | create_lockfiles = 1; | |
714 | ||
ffe75e6b | 715 | #ifdef CLASH_DETECTION |
8489eb67 RS |
716 | defsubr (&Sunlock_buffer); |
717 | defsubr (&Slock_buffer); | |
718 | defsubr (&Sfile_locked_p); | |
ffe75e6b | 719 | #endif |
8489eb67 | 720 | } |