Commit | Line | Data |
---|---|---|
b97771fc | 1 | /* Lock files for editing. |
ab422c4d PE |
2 | Copyright (C) 1985-1987, 1993-1994, 1996, 1998-2013 Free Software |
3 | 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" |
343a2aef | 46 | #ifdef WINDOWSNT |
531e70ec | 47 | #include <share.h> |
343a2aef EZ |
48 | #include "w32.h" /* for dostounix_filename */ |
49 | #endif | |
8489eb67 | 50 | |
8489eb67 | 51 | #ifdef CLASH_DETECTION |
e788eecc | 52 | |
c6d09b8d | 53 | #ifdef HAVE_UTMP_H |
e788eecc | 54 | #include <utmp.h> |
c6d09b8d | 55 | #endif |
77e544a4 | 56 | |
a48de9b2 PE |
57 | /* A file whose last-modified time is just after the most recent boot. |
58 | Define this to be NULL to disable checking for this file. */ | |
59 | #ifndef BOOT_TIME_FILE | |
60 | #define BOOT_TIME_FILE "/var/run/random-seed" | |
61 | #endif | |
62 | ||
77e544a4 RS |
63 | #ifndef WTMP_FILE |
64 | #define WTMP_FILE "/var/log/wtmp" | |
65 | #endif | |
177c0ea7 | 66 | |
b5029e23 PE |
67 | /* On non-MS-Windows systems, use a symbolic link to represent a lock. |
68 | The strategy: to lock a file FN, create a symlink .#FN in FN's | |
8dbbc384 RS |
69 | directory, with link data `user@host.pid'. This avoids a single |
70 | mount (== failure) point for lock files. | |
71 | ||
72 | When the host in the lock data is the current host, we can check if | |
73 | the pid is valid with kill. | |
177c0ea7 | 74 | |
8dbbc384 RS |
75 | Otherwise, we could look at a separate file that maps hostnames to |
76 | reboot times to see if the remote pid can possibly be valid, since we | |
77 | don't want Emacs to have to communicate via pipes or sockets or | |
78 | whatever to other processes, either locally or remotely; rms says | |
79 | that's too unreliable. Hence the separate file, which could | |
80 | theoretically be updated by daemons running separately -- but this | |
81 | whole idea is unimplemented; in practice, at least in our | |
1c4f857c | 82 | environment, it seems such stale locks arise fairly infrequently, and |
8dbbc384 RS |
83 | Emacs' standard methods of dealing with clashes suffice. |
84 | ||
85 | We use symlinks instead of normal files because (1) they can be | |
86 | stored more efficiently on the filesystem, since the kernel knows | |
87 | they will be small, and (2) all the info about the lock can be read | |
88 | in a single system call (readlink). Although we could use regular | |
1c4f857c | 89 | files to be useful on old systems lacking symlinks, nowadays |
8dbbc384 RS |
90 | virtually all such systems are probably single-user anyway, so it |
91 | didn't seem worth the complication. | |
177c0ea7 | 92 | |
8dbbc384 RS |
93 | Similarly, we don't worry about a possible 14-character limit on |
94 | file names, because those are all the same systems that don't have | |
95 | symlinks. | |
177c0ea7 | 96 | |
8dbbc384 RS |
97 | This is compatible with the locking scheme used by Interleaf (which |
98 | has contributed this implementation for Emacs), and was designed by | |
99 | Ethan Jacobson, Kimbo Mundy, and others. | |
177c0ea7 | 100 | |
b5029e23 PE |
101 | --karl@cs.umb.edu/karl@hq.ileaf.com. |
102 | ||
103 | On MS-Windows, symbolic links do not work well, so instead of a | |
104 | symlink .#FN -> 'user@host.pid', the lock is a regular file .#-FN | |
105 | with contents 'user@host.pid'. MS-Windows and non-MS-Windows | |
106 | versions of Emacs ignore each other's locks. */ | |
8489eb67 | 107 | |
8dbbc384 | 108 | \f |
15e88d21 RS |
109 | /* Return the time of the last system boot. */ |
110 | ||
111 | static time_t boot_time; | |
f75d7a91 | 112 | static bool boot_time_initialized; |
15e88d21 | 113 | |
2f2500ef | 114 | #ifdef BOOT_TIME |
f75d7a91 | 115 | static void get_boot_time_1 (const char *, bool); |
2f2500ef DL |
116 | #endif |
117 | ||
15e88d21 | 118 | static time_t |
971de7fb | 119 | get_boot_time (void) |
15e88d21 | 120 | { |
9d2818d6 | 121 | #if defined (BOOT_TIME) |
9177d978 | 122 | int counter; |
2decc5a9 | 123 | #endif |
15e88d21 | 124 | |
b97771fc | 125 | if (boot_time_initialized) |
15e88d21 | 126 | return boot_time; |
b97771fc | 127 | boot_time_initialized = 1; |
15e88d21 | 128 | |
f805a125 KH |
129 | #if defined (CTL_KERN) && defined (KERN_BOOTTIME) |
130 | { | |
131 | int mib[2]; | |
132 | size_t size; | |
133 | struct timeval boottime_val; | |
134 | ||
135 | mib[0] = CTL_KERN; | |
136 | mib[1] = KERN_BOOTTIME; | |
137 | size = sizeof (boottime_val); | |
138 | ||
139 | if (sysctl (mib, 2, &boottime_val, &size, NULL, 0) >= 0) | |
140 | { | |
141 | boot_time = boottime_val.tv_sec; | |
142 | return boot_time; | |
143 | } | |
144 | } | |
145 | #endif /* defined (CTL_KERN) && defined (KERN_BOOTTIME) */ | |
9177d978 | 146 | |
a48de9b2 PE |
147 | if (BOOT_TIME_FILE) |
148 | { | |
149 | struct stat st; | |
150 | if (stat (BOOT_TIME_FILE, &st) == 0) | |
151 | { | |
152 | boot_time = st.st_mtime; | |
153 | return boot_time; | |
154 | } | |
155 | } | |
156 | ||
9d2818d6 | 157 | #if defined (BOOT_TIME) |
b97771fc RS |
158 | #ifndef CANNOT_DUMP |
159 | /* The utmp routines maintain static state. | |
160 | Don't touch that state unless we are initialized, | |
161 | since it might not survive dumping. */ | |
162 | if (! initialized) | |
163 | return boot_time; | |
164 | #endif /* not CANNOT_DUMP */ | |
165 | ||
166 | /* Try to get boot time from utmp before wtmp, | |
167 | since utmp is typically much smaller than wtmp. | |
168 | Passing a null pointer causes get_boot_time_1 | |
169 | to inspect the default file, namely utmp. */ | |
170 | get_boot_time_1 ((char *) 0, 0); | |
171 | if (boot_time) | |
172 | return boot_time; | |
173 | ||
9177d978 | 174 | /* Try to get boot time from the current wtmp file. */ |
b97771fc | 175 | get_boot_time_1 (WTMP_FILE, 1); |
9177d978 RS |
176 | |
177 | /* If we did not find a boot time in wtmp, look at wtmp, and so on. */ | |
b97771fc | 178 | for (counter = 0; counter < 20 && ! boot_time; counter++) |
9177d978 | 179 | { |
882f0d81 | 180 | char cmd_string[sizeof WTMP_FILE ".19.gz"]; |
9177d978 | 181 | Lisp_Object tempname, filename; |
f75d7a91 | 182 | bool delete_flag = 0; |
9177d978 RS |
183 | |
184 | filename = Qnil; | |
185 | ||
a8290ec3 DA |
186 | tempname = make_formatted_string |
187 | (cmd_string, "%s.%d", WTMP_FILE, counter); | |
29a2adb0 | 188 | if (! NILP (Ffile_exists_p (tempname))) |
9177d978 RS |
189 | filename = tempname; |
190 | else | |
191 | { | |
a8290ec3 DA |
192 | tempname = make_formatted_string (cmd_string, "%s.%d.gz", |
193 | WTMP_FILE, counter); | |
9177d978 RS |
194 | if (! NILP (Ffile_exists_p (tempname))) |
195 | { | |
196 | Lisp_Object args[6]; | |
f1d367aa GM |
197 | |
198 | /* The utmp functions on mescaline.gnu.org accept only | |
199 | file names up to 8 characters long. Choose a 2 | |
200 | character long prefix, and call make_temp_file with | |
201 | second arg non-zero, so that it will add not more | |
202 | than 6 characters to the prefix. */ | |
882f0d81 | 203 | filename = Fexpand_file_name (build_string ("wt"), |
5f8d6a10 | 204 | Vtemporary_file_directory); |
882f0d81 PE |
205 | filename = make_temp_name (filename, 1); |
206 | args[0] = build_string ("gzip"); | |
9177d978 | 207 | args[1] = Qnil; |
882f0d81 | 208 | args[2] = list2 (QCfile, filename); |
9177d978 | 209 | args[3] = Qnil; |
882f0d81 PE |
210 | args[4] = build_string ("-cd"); |
211 | args[5] = tempname; | |
9177d978 | 212 | Fcall_process (6, args); |
9177d978 RS |
213 | delete_flag = 1; |
214 | } | |
215 | } | |
216 | ||
217 | if (! NILP (filename)) | |
218 | { | |
42a5b22f | 219 | get_boot_time_1 (SSDATA (filename), 1); |
9177d978 | 220 | if (delete_flag) |
42a5b22f | 221 | unlink (SSDATA (filename)); |
9177d978 RS |
222 | } |
223 | } | |
224 | ||
225 | return boot_time; | |
226 | #else | |
227 | return 0; | |
228 | #endif | |
229 | } | |
230 | ||
e9f22ced | 231 | #ifdef BOOT_TIME |
9177d978 RS |
232 | /* Try to get the boot time from wtmp file FILENAME. |
233 | This succeeds if that file contains a reboot record. | |
9177d978 | 234 | |
b97771fc RS |
235 | If FILENAME is zero, use the same file as before; |
236 | if no FILENAME has ever been specified, this is the utmp file. | |
f75d7a91 | 237 | Use the newest reboot record if NEWEST, |
b97771fc RS |
238 | the first reboot record otherwise. |
239 | Ignore all reboot records on or before BOOT_TIME. | |
240 | Success is indicated by setting BOOT_TIME to a larger value. */ | |
241 | ||
2f2500ef | 242 | void |
f75d7a91 | 243 | get_boot_time_1 (const char *filename, bool newest) |
9177d978 RS |
244 | { |
245 | struct utmp ut, *utp; | |
77e544a4 RS |
246 | int desc; |
247 | ||
b97771fc RS |
248 | if (filename) |
249 | { | |
250 | /* On some versions of IRIX, opening a nonexistent file name | |
251 | is likely to crash in the utmp routines. */ | |
68c45bf0 | 252 | desc = emacs_open (filename, O_RDONLY, 0); |
b97771fc RS |
253 | if (desc < 0) |
254 | return; | |
255 | ||
68c45bf0 | 256 | emacs_close (desc); |
b97771fc RS |
257 | |
258 | utmpname (filename); | |
259 | } | |
9177d978 | 260 | |
c321b190 | 261 | setutent (); |
b97771fc | 262 | |
c321b190 RS |
263 | while (1) |
264 | { | |
265 | /* Find the next reboot record. */ | |
266 | ut.ut_type = BOOT_TIME; | |
267 | utp = getutid (&ut); | |
268 | if (! utp) | |
269 | break; | |
270 | /* Compare reboot times and use the newest one. */ | |
271 | if (utp->ut_time > boot_time) | |
b97771fc RS |
272 | { |
273 | boot_time = utp->ut_time; | |
274 | if (! newest) | |
275 | break; | |
276 | } | |
c321b190 RS |
277 | /* Advance on element in the file |
278 | so that getutid won't repeat the same one. */ | |
279 | utp = getutent (); | |
280 | if (! utp) | |
281 | break; | |
282 | } | |
15e88d21 | 283 | endutent (); |
15e88d21 | 284 | } |
e9f22ced | 285 | #endif /* BOOT_TIME */ |
15e88d21 | 286 | \f |
8dbbc384 | 287 | /* Here is the structure that stores information about a lock. */ |
32676c08 | 288 | |
8dbbc384 RS |
289 | typedef struct |
290 | { | |
291 | char *user; | |
292 | char *host; | |
882f0d81 | 293 | pid_t pid; |
15e88d21 | 294 | time_t boot_time; |
8dbbc384 | 295 | } lock_info_type; |
32676c08 | 296 | |
8dbbc384 RS |
297 | /* Free the two dynamically-allocated pieces in PTR. */ |
298 | #define FREE_LOCK_INFO(i) do { xfree ((i).user); xfree ((i).host); } while (0) | |
e31fbc7a | 299 | |
343a2aef | 300 | #ifdef WINDOWSNT |
b5029e23 | 301 | enum { defined_WINDOWSNT = 1 }; |
343a2aef | 302 | #else |
b5029e23 | 303 | enum { defined_WINDOWSNT = 0 }; |
343a2aef | 304 | #endif |
e31fbc7a | 305 | |
b5029e23 PE |
306 | /* Write the name of the lock file for FNAME into LOCKNAME. Length |
307 | will be that of FNAME plus two more for the leading ".#", | |
308 | plus one for "-" if MS-Windows, plus one for the null. */ | |
309 | #define MAKE_LOCK_NAME(lockname, fname) \ | |
310 | (lockname = SAFE_ALLOCA (SBYTES (fname) + 2 + defined_WINDOWSNT + 1), \ | |
311 | fill_in_lock_file_name (lockname, fname)) | |
312 | ||
8dbbc384 | 313 | static void |
b5029e23 | 314 | fill_in_lock_file_name (char *lockfile, Lisp_Object fn) |
e31fbc7a | 315 | { |
b5029e23 PE |
316 | char *last_slash = memrchr (SSDATA (fn), '/', SBYTES (fn)); |
317 | char *base = last_slash + 1; | |
318 | ptrdiff_t dirlen = base - SSDATA (fn); | |
319 | memcpy (lockfile, SSDATA (fn), dirlen); | |
320 | lockfile[dirlen] = '.'; | |
321 | lockfile[dirlen + 1] = '#'; | |
322 | if (defined_WINDOWSNT) | |
323 | lockfile[dirlen + 2] = '-'; | |
324 | strcpy (lockfile + dirlen + 2 + defined_WINDOWSNT, base); | |
8dbbc384 | 325 | } |
e31fbc7a | 326 | |
343a2aef EZ |
327 | static int |
328 | create_lock_file (char *lfname, char *lock_info_str, bool force) | |
329 | { | |
330 | int err; | |
331 | ||
332 | #ifdef WINDOWSNT | |
333 | /* Symlinks are supported only by latest versions of Windows, and | |
334 | creating them is a privileged operation that often triggers UAC | |
335 | elevation prompts. Therefore, instead of using symlinks, we | |
336 | create a regular file with the lock info written as its | |
337 | contents. */ | |
338 | { | |
531e70ec EZ |
339 | /* Deny everybody else any kind of access to the file until we are |
340 | done writing it and close the handle. This makes the entire | |
b5029e23 PE |
341 | open/write/close operation atomic, as far as other WINDOWSNT |
342 | processes are concerned. */ | |
531e70ec EZ |
343 | int fd = _sopen (lfname, |
344 | _O_WRONLY | _O_BINARY | _O_CREAT | _O_EXCL | _O_NOINHERIT, | |
345 | _SH_DENYRW, S_IREAD | S_IWRITE); | |
343a2aef EZ |
346 | |
347 | if (fd < 0 && errno == EEXIST && force) | |
531e70ec EZ |
348 | fd = _sopen (lfname, _O_WRONLY | _O_BINARY | _O_TRUNC |_O_NOINHERIT, |
349 | _SH_DENYRW, S_IREAD | S_IWRITE); | |
343a2aef EZ |
350 | if (fd >= 0) |
351 | { | |
352 | ssize_t lock_info_len = strlen (lock_info_str); | |
353 | ||
354 | err = 0; | |
355 | if (emacs_write (fd, lock_info_str, lock_info_len) != lock_info_len) | |
356 | err = -1; | |
357 | if (emacs_close (fd)) | |
358 | err = -1; | |
359 | } | |
360 | else | |
361 | err = -1; | |
362 | } | |
363 | #else | |
364 | err = symlink (lock_info_str, lfname); | |
b5029e23 | 365 | if (err != 0 && errno == EEXIST && force) |
343a2aef EZ |
366 | { |
367 | unlink (lfname); | |
368 | err = symlink (lock_info_str, lfname); | |
369 | } | |
370 | #endif | |
371 | ||
372 | return err; | |
373 | } | |
374 | ||
8dbbc384 | 375 | /* Lock the lock file named LFNAME. |
f75d7a91 PE |
376 | If FORCE, do so even if it is already locked. |
377 | Return true if successful. */ | |
e31fbc7a | 378 | |
f75d7a91 PE |
379 | static bool |
380 | lock_file_1 (char *lfname, bool force) | |
8dbbc384 | 381 | { |
98c6f1e3 | 382 | int err; |
b5cd1905 PE |
383 | int symlink_errno; |
384 | USE_SAFE_ALLOCA; | |
662c2ef2 | 385 | |
4ba93ac0 | 386 | /* Call this first because it can GC. */ |
98c6f1e3 PE |
387 | printmax_t boot = get_boot_time (); |
388 | ||
389 | Lisp_Object luser_name = Fuser_login_name (Qnil); | |
390 | char const *user_name = STRINGP (luser_name) ? SSDATA (luser_name) : ""; | |
391 | Lisp_Object lhost_name = Fsystem_name (); | |
392 | char const *host_name = STRINGP (lhost_name) ? SSDATA (lhost_name) : ""; | |
393 | ptrdiff_t lock_info_size = (strlen (user_name) + strlen (host_name) | |
394 | + 2 * INT_STRLEN_BOUND (printmax_t) | |
395 | + sizeof "@.:"); | |
396 | char *lock_info_str = SAFE_ALLOCA (lock_info_size); | |
397 | printmax_t pid = getpid (); | |
8dbbc384 | 398 | |
b5cd1905 PE |
399 | esprintf (lock_info_str, boot ? "%s@%s.%"pMd":%"pMd : "%s@%s.%"pMd, |
400 | user_name, host_name, pid, boot); | |
343a2aef | 401 | err = create_lock_file (lfname, lock_info_str, force); |
e31fbc7a | 402 | |
b5cd1905 PE |
403 | symlink_errno = errno; |
404 | SAFE_FREE (); | |
405 | errno = symlink_errno; | |
8dbbc384 RS |
406 | return err == 0; |
407 | } | |
e31fbc7a | 408 | |
f75d7a91 | 409 | /* Return true if times A and B are no more than one second apart. */ |
32676c08 | 410 | |
f75d7a91 | 411 | static bool |
971de7fb | 412 | within_one_second (time_t a, time_t b) |
9177d978 RS |
413 | { |
414 | return (a - b >= -1 && a - b <= 1); | |
415 | } | |
8dbbc384 | 416 | \f |
343a2aef EZ |
417 | static Lisp_Object |
418 | read_lock_data (char *lfname) | |
419 | { | |
420 | #ifndef WINDOWSNT | |
421 | return emacs_readlinkat (AT_FDCWD, lfname); | |
422 | #else | |
423 | int fd = emacs_open (lfname, O_RDONLY | O_BINARY, S_IREAD); | |
424 | ssize_t nbytes; | |
b5029e23 PE |
425 | /* 256 chars for user, 1024 chars for host, 10 digits for each of 2 int's. */ |
426 | enum { MAX_LFINFO = 256 + 1024 + 10 + 10 + 2 }; | |
343a2aef EZ |
427 | char lfinfo[MAX_LFINFO + 1]; |
428 | ||
429 | if (fd < 0) | |
430 | return Qnil; | |
431 | ||
432 | nbytes = emacs_read (fd, lfinfo, MAX_LFINFO); | |
433 | emacs_close (fd); | |
434 | ||
435 | if (nbytes > 0) | |
436 | { | |
437 | lfinfo[nbytes] = '\0'; | |
438 | return build_string (lfinfo); | |
439 | } | |
440 | else | |
441 | return Qnil; | |
442 | #endif | |
443 | } | |
444 | ||
8dbbc384 RS |
445 | /* Return 0 if nobody owns the lock file LFNAME or the lock is obsolete, |
446 | 1 if another process owns it (and set OWNER (if non-null) to info), | |
447 | 2 if the current process owns it, | |
448 | or -1 if something is wrong with the locking mechanism. */ | |
e31fbc7a | 449 | |
8dbbc384 | 450 | static int |
971de7fb | 451 | current_lock_owner (lock_info_type *owner, char *lfname) |
32676c08 | 452 | { |
d1fdcab7 | 453 | int ret; |
882f0d81 PE |
454 | ptrdiff_t len; |
455 | lock_info_type local_owner; | |
456 | intmax_t n; | |
15e88d21 | 457 | char *at, *dot, *colon; |
343a2aef | 458 | Lisp_Object lfinfo_object = read_lock_data (lfname); |
8654f9d7 PE |
459 | char *lfinfo; |
460 | struct gcpro gcpro1; | |
177c0ea7 | 461 | |
8dbbc384 | 462 | /* If nonexistent lock file, all is well; otherwise, got strange error. */ |
8654f9d7 | 463 | if (NILP (lfinfo_object)) |
d1fdcab7 | 464 | return errno == ENOENT ? 0 : -1; |
8654f9d7 | 465 | lfinfo = SSDATA (lfinfo_object); |
177c0ea7 | 466 | |
8dbbc384 | 467 | /* Even if the caller doesn't want the owner info, we still have to |
882f0d81 | 468 | read it to determine return value. */ |
8dbbc384 | 469 | if (!owner) |
882f0d81 | 470 | owner = &local_owner; |
177c0ea7 | 471 | |
15e88d21 | 472 | /* Parse USER@HOST.PID:BOOT_TIME. If can't parse, return -1. */ |
50624218 | 473 | /* The USER is everything before the last @. */ |
8966b757 AS |
474 | at = strrchr (lfinfo, '@'); |
475 | dot = strrchr (lfinfo, '.'); | |
15e88d21 | 476 | if (!at || !dot) |
8654f9d7 | 477 | return -1; |
8dbbc384 | 478 | len = at - lfinfo; |
8654f9d7 | 479 | GCPRO1 (lfinfo_object); |
23f86fce | 480 | owner->user = xmalloc (len + 1); |
882f0d81 | 481 | memcpy (owner->user, lfinfo, len); |
8dbbc384 | 482 | owner->user[len] = 0; |
177c0ea7 | 483 | |
15e88d21 | 484 | /* The PID is everything from the last `.' to the `:'. */ |
882f0d81 PE |
485 | errno = 0; |
486 | n = strtoimax (dot + 1, NULL, 10); | |
487 | owner->pid = | |
488 | ((0 <= n && n <= TYPE_MAXIMUM (pid_t) | |
489 | && (TYPE_MAXIMUM (pid_t) < INTMAX_MAX || errno != ERANGE)) | |
490 | ? n : 0); | |
491 | ||
492 | colon = strchr (dot + 1, ':'); | |
15e88d21 | 493 | /* After the `:', if there is one, comes the boot time. */ |
882f0d81 PE |
494 | n = 0; |
495 | if (colon) | |
496 | { | |
497 | errno = 0; | |
498 | n = strtoimax (colon + 1, NULL, 10); | |
499 | } | |
500 | owner->boot_time = | |
501 | ((0 <= n && n <= TYPE_MAXIMUM (time_t) | |
502 | && (TYPE_MAXIMUM (time_t) < INTMAX_MAX || errno != ERANGE)) | |
503 | ? n : 0); | |
32676c08 | 504 | |
8dbbc384 RS |
505 | /* The host is everything in between. */ |
506 | len = dot - at - 1; | |
23f86fce | 507 | owner->host = xmalloc (len + 1); |
882f0d81 | 508 | memcpy (owner->host, at + 1, len); |
8dbbc384 | 509 | owner->host[len] = 0; |
32676c08 | 510 | |
8dbbc384 | 511 | /* We're done looking at the link info. */ |
8654f9d7 | 512 | UNGCPRO; |
177c0ea7 | 513 | |
8dbbc384 | 514 | /* On current host? */ |
662c2ef2 | 515 | if (STRINGP (Fsystem_name ()) |
42a5b22f | 516 | && strcmp (owner->host, SSDATA (Fsystem_name ())) == 0) |
32676c08 | 517 | { |
8dbbc384 RS |
518 | if (owner->pid == getpid ()) |
519 | ret = 2; /* We own it. */ | |
72dcef0e | 520 | else if (owner->pid > 0 |
15e88d21 RS |
521 | && (kill (owner->pid, 0) >= 0 || errno == EPERM) |
522 | && (owner->boot_time == 0 | |
9177d978 | 523 | || within_one_second (owner->boot_time, get_boot_time ()))) |
8dbbc384 | 524 | ret = 1; /* An existing process on this machine owns it. */ |
8dbbc384 RS |
525 | /* The owner process is dead or has a strange pid (<=0), so try to |
526 | zap the lockfile. */ | |
72dcef0e | 527 | else if (unlink (lfname) < 0) |
8dbbc384 | 528 | ret = -1; |
72dcef0e RS |
529 | else |
530 | ret = 0; | |
32676c08 | 531 | } |
8dbbc384 RS |
532 | else |
533 | { /* If we wanted to support the check for stale locks on remote machines, | |
534 | here's where we'd do it. */ | |
535 | ret = 1; | |
536 | } | |
177c0ea7 | 537 | |
8dbbc384 | 538 | /* Avoid garbage. */ |
882f0d81 | 539 | if (owner == &local_owner || ret <= 0) |
8dbbc384 RS |
540 | { |
541 | FREE_LOCK_INFO (*owner); | |
542 | } | |
543 | return ret; | |
32676c08 JB |
544 | } |
545 | ||
8dbbc384 RS |
546 | \f |
547 | /* Lock the lock named LFNAME if possible. | |
548 | Return 0 in that case. | |
549 | Return positive if some other process owns the lock, and info about | |
550 | that process in CLASHER. | |
551 | Return -1 if cannot lock for any other reason. */ | |
8489eb67 | 552 | |
8dbbc384 | 553 | static int |
971de7fb | 554 | lock_if_free (lock_info_type *clasher, register char *lfname) |
8dbbc384 | 555 | { |
f75d7a91 | 556 | while (! lock_file_1 (lfname, 0)) |
8dbbc384 RS |
557 | { |
558 | int locker; | |
e0e0205b | 559 | |
8dbbc384 RS |
560 | if (errno != EEXIST) |
561 | return -1; | |
177c0ea7 | 562 | |
8dbbc384 RS |
563 | locker = current_lock_owner (clasher, lfname); |
564 | if (locker == 2) | |
565 | { | |
566 | FREE_LOCK_INFO (*clasher); | |
567 | return 0; /* We ourselves locked it. */ | |
568 | } | |
569 | else if (locker == 1) | |
570 | return 1; /* Someone else has it. */ | |
5df0b2fa | 571 | else if (locker == -1) |
ae1ef097 | 572 | return -1; /* current_lock_owner returned strange error. */ |
8dbbc384 | 573 | |
cfc01fa7 | 574 | /* We deleted a stale lock; try again to lock the file. */ |
8dbbc384 RS |
575 | } |
576 | return 0; | |
8489eb67 RS |
577 | } |
578 | ||
8dbbc384 | 579 | /* lock_file locks file FN, |
8489eb67 RS |
580 | meaning it serves notice on the world that you intend to edit that file. |
581 | This should be done only when about to modify a file-visiting | |
582 | buffer previously unmodified. | |
8dbbc384 | 583 | Do not (normally) call this for a buffer already modified, |
8489eb67 RS |
584 | as either the file is already locked, or the user has already |
585 | decided to go ahead without locking. | |
586 | ||
8dbbc384 | 587 | When this returns, either the lock is locked for us, |
b5029e23 | 588 | or lock creation failed, |
8489eb67 RS |
589 | or the user has said to go ahead without locking. |
590 | ||
8dbbc384 | 591 | If the file is locked by someone else, this calls |
8489eb67 | 592 | ask-user-about-lock (a Lisp function) with two arguments, |
8dbbc384 | 593 | the file name and info about the user who did the locking. |
8489eb67 RS |
594 | This function can signal an error, or return t meaning |
595 | take away the lock, or return nil meaning ignore the lock. */ | |
596 | ||
8489eb67 | 597 | void |
971de7fb | 598 | lock_file (Lisp_Object fn) |
8489eb67 | 599 | { |
2db41375 PE |
600 | Lisp_Object orig_fn, encoded_fn; |
601 | char *lfname; | |
8dbbc384 | 602 | lock_info_type lock_info; |
3edc33a4 | 603 | struct gcpro gcpro1; |
b5cd1905 | 604 | USE_SAFE_ALLOCA; |
8489eb67 | 605 | |
836d29b3 DA |
606 | /* Don't do locking if the user has opted out. */ |
607 | if (! create_lockfiles) | |
608 | return; | |
609 | ||
33bae690 RS |
610 | /* Don't do locking while dumping Emacs. |
611 | Uncompressing wtmp files uses call-process, which does not work | |
612 | in an uninitialized Emacs. */ | |
613 | if (! NILP (Vpurify_flag)) | |
614 | return; | |
615 | ||
5383bc6d | 616 | orig_fn = fn; |
8af8a9ca | 617 | GCPRO1 (fn); |
1e89de84 | 618 | fn = Fexpand_file_name (fn, Qnil); |
343a2aef EZ |
619 | #ifdef WINDOWSNT |
620 | /* Ensure we have only '/' separators, to avoid problems with | |
621 | looking (inside fill_in_lock_file_name) for backslashes in file | |
622 | names encoded by some DBCS codepage. */ | |
623 | dostounix_filename (SSDATA (fn), 1); | |
624 | #endif | |
f4a4528d | 625 | encoded_fn = ENCODE_FILE (fn); |
1e89de84 | 626 | |
8dbbc384 | 627 | /* Create the name of the lock-file for file fn */ |
f4a4528d | 628 | MAKE_LOCK_NAME (lfname, encoded_fn); |
8489eb67 | 629 | |
32676c08 JB |
630 | /* See if this file is visited and has changed on disk since it was |
631 | visited. */ | |
8489eb67 | 632 | { |
a57bc488 | 633 | register Lisp_Object subject_buf; |
3036594f | 634 | |
5383bc6d | 635 | subject_buf = get_truename_buffer (orig_fn); |
3036594f | 636 | |
265a9e55 JB |
637 | if (!NILP (subject_buf) |
638 | && NILP (Fverify_visited_file_modtime (subject_buf)) | |
639 | && !NILP (Ffile_exists_p (fn))) | |
8489eb67 | 640 | call1 (intern ("ask-user-about-supersession-threat"), fn); |
3036594f | 641 | |
8489eb67 | 642 | } |
8489eb67 | 643 | |
2db41375 PE |
644 | /* Try to lock the lock. */ |
645 | if (0 < lock_if_free (&lock_info, lfname)) | |
8489eb67 | 646 | { |
2db41375 PE |
647 | /* Someone else has the lock. Consider breaking it. */ |
648 | ptrdiff_t locker_size = (strlen (lock_info.user) + strlen (lock_info.host) | |
649 | + INT_STRLEN_BOUND (printmax_t) | |
650 | + sizeof "@ (pid )"); | |
651 | char *locker = SAFE_ALLOCA (locker_size); | |
652 | printmax_t pid = lock_info.pid; | |
653 | Lisp_Object attack; | |
654 | esprintf (locker, "%s@%s (pid %"pMd")", | |
655 | lock_info.user, lock_info.host, pid); | |
656 | FREE_LOCK_INFO (lock_info); | |
657 | ||
658 | attack = call2 (intern ("ask-user-about-lock"), fn, build_string (locker)); | |
659 | /* Take the lock if the user said so. */ | |
660 | if (!NILP (attack)) | |
661 | lock_file_1 (lfname, 1); | |
8489eb67 | 662 | } |
2db41375 PE |
663 | |
664 | UNGCPRO; | |
665 | SAFE_FREE (); | |
8489eb67 RS |
666 | } |
667 | ||
8489eb67 | 668 | void |
b5029e23 | 669 | unlock_file (Lisp_Object fn) |
8489eb67 | 670 | { |
b5029e23 PE |
671 | char *lfname; |
672 | USE_SAFE_ALLOCA; | |
8489eb67 | 673 | |
1e89de84 | 674 | fn = Fexpand_file_name (fn, Qnil); |
88eace34 | 675 | fn = ENCODE_FILE (fn); |
1e89de84 | 676 | |
7b92975f | 677 | MAKE_LOCK_NAME (lfname, fn); |
8489eb67 | 678 | |
8dbbc384 | 679 | if (current_lock_owner (0, lfname) == 2) |
8489eb67 | 680 | unlink (lfname); |
b5029e23 PE |
681 | |
682 | SAFE_FREE (); | |
8489eb67 RS |
683 | } |
684 | ||
685 | void | |
971de7fb | 686 | unlock_all_files (void) |
8489eb67 RS |
687 | { |
688 | register Lisp_Object tail; | |
689 | register struct buffer *b; | |
690 | ||
8e50cc2d | 691 | for (tail = Vbuffer_alist; CONSP (tail); tail = XCDR (tail)) |
8489eb67 | 692 | { |
03699b14 | 693 | b = XBUFFER (XCDR (XCAR (tail))); |
4b4deea2 | 694 | if (STRINGP (BVAR (b, file_truename)) && BUF_SAVE_MODIFF (b) < BUF_MODIFF (b)) |
1c343051 | 695 | { |
5e617bc2 | 696 | unlock_file (BVAR (b, file_truename)); |
1c343051 | 697 | } |
8489eb67 RS |
698 | } |
699 | } | |
8489eb67 RS |
700 | \f |
701 | DEFUN ("lock-buffer", Flock_buffer, Slock_buffer, | |
335c5470 PJ |
702 | 0, 1, 0, |
703 | doc: /* Lock FILE, if current buffer is modified. | |
704 | FILE defaults to current buffer's visited file, | |
705 | or else nothing is done if current buffer isn't visiting a file. */) | |
5842a27b | 706 | (Lisp_Object file) |
8489eb67 | 707 | { |
e9319ef2 | 708 | if (NILP (file)) |
4b4deea2 | 709 | file = BVAR (current_buffer, file_truename); |
8489eb67 | 710 | else |
b7826503 | 711 | CHECK_STRING (file); |
6a140159 | 712 | if (SAVE_MODIFF < MODIFF |
e9319ef2 EN |
713 | && !NILP (file)) |
714 | lock_file (file); | |
177c0ea7 | 715 | return Qnil; |
8489eb67 RS |
716 | } |
717 | ||
a7ca3326 | 718 | DEFUN ("unlock-buffer", Funlock_buffer, Sunlock_buffer, |
335c5470 | 719 | 0, 0, 0, |
3bfb8921 RS |
720 | doc: /* Unlock the file visited in the current buffer. |
721 | If the buffer is not modified, this does nothing because the file | |
722 | should not be locked in that case. */) | |
5842a27b | 723 | (void) |
8489eb67 | 724 | { |
6a140159 | 725 | if (SAVE_MODIFF < MODIFF |
4b4deea2 TT |
726 | && STRINGP (BVAR (current_buffer, file_truename))) |
727 | unlock_file (BVAR (current_buffer, file_truename)); | |
8489eb67 RS |
728 | return Qnil; |
729 | } | |
730 | ||
8489eb67 RS |
731 | /* Unlock the file visited in buffer BUFFER. */ |
732 | ||
d07e0802 | 733 | void |
971de7fb | 734 | unlock_buffer (struct buffer *buffer) |
8489eb67 | 735 | { |
6a140159 | 736 | if (BUF_SAVE_MODIFF (buffer) < BUF_MODIFF (buffer) |
4b4deea2 TT |
737 | && STRINGP (BVAR (buffer, file_truename))) |
738 | unlock_file (BVAR (buffer, file_truename)); | |
8489eb67 RS |
739 | } |
740 | ||
8105cbf7 | 741 | DEFUN ("file-locked-p", Ffile_locked_p, Sfile_locked_p, 1, 1, 0, |
3bfb8921 RS |
742 | doc: /* Return a value indicating whether FILENAME is locked. |
743 | The value is nil if the FILENAME is not locked, | |
744 | t if it is locked by you, else a string saying which user has locked it. */) | |
5842a27b | 745 | (Lisp_Object filename) |
8489eb67 | 746 | { |
8dbbc384 | 747 | Lisp_Object ret; |
b5029e23 | 748 | char *lfname; |
8489eb67 | 749 | int owner; |
8dbbc384 | 750 | lock_info_type locker; |
b5029e23 | 751 | USE_SAFE_ALLOCA; |
8489eb67 | 752 | |
e9319ef2 | 753 | filename = Fexpand_file_name (filename, Qnil); |
8489eb67 | 754 | |
e9319ef2 | 755 | MAKE_LOCK_NAME (lfname, filename); |
8489eb67 | 756 | |
8dbbc384 | 757 | owner = current_lock_owner (&locker, lfname); |
8489eb67 | 758 | if (owner <= 0) |
8dbbc384 RS |
759 | ret = Qnil; |
760 | else if (owner == 2) | |
761 | ret = Qt; | |
762 | else | |
763 | ret = build_string (locker.user); | |
764 | ||
765 | if (owner > 0) | |
766 | FREE_LOCK_INFO (locker); | |
767 | ||
b5029e23 | 768 | SAFE_FREE (); |
8dbbc384 | 769 | return ret; |
8489eb67 | 770 | } |
a3fd58aa | 771 | |
ffe75e6b EZ |
772 | #endif /* CLASH_DETECTION */ |
773 | ||
dfcf069d | 774 | void |
971de7fb | 775 | syms_of_filelock (void) |
8489eb67 | 776 | { |
29208e82 | 777 | DEFVAR_LISP ("temporary-file-directory", Vtemporary_file_directory, |
335c5470 | 778 | doc: /* The directory for writing temporary files. */); |
5f8d6a10 RS |
779 | Vtemporary_file_directory = Qnil; |
780 | ||
836d29b3 DA |
781 | DEFVAR_BOOL ("create-lockfiles", create_lockfiles, |
782 | doc: /* Non-nil means use lockfiles to avoid editing collisions. */); | |
783 | create_lockfiles = 1; | |
784 | ||
ffe75e6b | 785 | #ifdef CLASH_DETECTION |
8489eb67 RS |
786 | defsubr (&Sunlock_buffer); |
787 | defsubr (&Slock_buffer); | |
788 | defsubr (&Sfile_locked_p); | |
ffe75e6b | 789 | #endif |
8489eb67 | 790 | } |