summaryrefslogtreecommitdiffstats
path: root/src/shared/watchdog.c
blob: 8871476bdcea252df71bf58b63b6d4527a04578e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <syslog.h>
#include <unistd.h>
#include <linux/watchdog.h>

#include "devnum-util.h"
#include "errno-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "log.h"
#include "path-util.h"
#include "string-util.h"
#include "time-util.h"
#include "watchdog.h"

static int watchdog_fd = -1;
static char *watchdog_device = NULL;
static usec_t watchdog_timeout = 0; /* 0 → close device and USEC_INFINITY → don't change timeout */
static usec_t watchdog_pretimeout = 0; /* 0 → disable pretimeout and USEC_INFINITY → don't change pretimeout */
static usec_t watchdog_last_ping = USEC_INFINITY;
static bool watchdog_supports_pretimeout = false; /* Depends on kernel state that might change at runtime */
static char *watchdog_pretimeout_governor = NULL;

/* Starting from kernel version 4.5, the maximum allowable watchdog timeout is
 * UINT_MAX/1000U seconds (since internal calculations are done in milliseconds
 * using unsigned integers. However, the kernel's userspace API for the watchdog
 * uses signed integers for its ioctl parameters (even for timeout values and
 * bit flags) so this is why we must consider the maximum signed integer value
 * as well.
 */
#define WATCHDOG_TIMEOUT_MAX_SEC (CONST_MIN(UINT_MAX/1000U, (unsigned)INT_MAX))

#define WATCHDOG_GOV_NAME_MAXLEN 20 /* From the kernel watchdog driver */

static int saturated_usec_to_sec(usec_t val) {
        usec_t t = DIV_ROUND_UP(val, USEC_PER_SEC);
        return MIN(t, (usec_t) WATCHDOG_TIMEOUT_MAX_SEC); /* Saturate to watchdog max */
}

static int get_watchdog_sysfs_path(const char *filename, char **ret_path) {
        struct stat st;

        if (watchdog_fd < 0)
                return -EBADF;

        if (fstat(watchdog_fd, &st))
                return -errno;

        if (!S_ISCHR(st.st_mode))
                return -EBADF;

        if (asprintf(ret_path, "/sys/dev/char/"DEVNUM_FORMAT_STR"/%s", DEVNUM_FORMAT_VAL(st.st_rdev), filename) < 0)
                return -ENOMEM;

        return 0;
}

static int get_pretimeout_governor(char **ret_gov) {
        _cleanup_free_ char *sys_fn = NULL;
        int r;

        r = get_watchdog_sysfs_path("pretimeout_governor", &sys_fn);
        if (r < 0)
                return r;

        log_info("Watchdog: reading from %s", sys_fn);

        r = read_virtual_file(sys_fn, WATCHDOG_GOV_NAME_MAXLEN - 1, ret_gov, NULL);
        if (r < 0)
                return r;

        delete_trailing_chars(*ret_gov, WHITESPACE);

        return 0;
}

static int set_pretimeout_governor(const char *governor) {
        _cleanup_free_ char *sys_fn = NULL;
        int r;

        if (isempty(governor))
                return 0; /* Nothing to do */

        r = get_watchdog_sysfs_path("pretimeout_governor", &sys_fn);
        if (r < 0)
                return r;

        log_info("Watchdog: setting pretimeout_governor to '%s' via '%s'", governor, sys_fn);

        r = write_string_file(sys_fn,
                              governor,
                              WRITE_STRING_FILE_DISABLE_BUFFER | WRITE_STRING_FILE_VERIFY_ON_FAILURE | WRITE_STRING_FILE_VERIFY_IGNORE_NEWLINE);
        if (r < 0)
                return log_error_errno(r, "Failed to set pretimeout_governor to '%s': %m", governor);

        return r;
}

static int watchdog_set_enable(bool enable) {
        int flags = enable ? WDIOS_ENABLECARD : WDIOS_DISABLECARD;

        assert(watchdog_fd >= 0);

        if (ioctl(watchdog_fd, WDIOC_SETOPTIONS, &flags) < 0) {
                if (!enable)
                        return log_warning_errno(errno, "Failed to disable hardware watchdog, ignoring: %m");

                /* ENOTTY means the watchdog is always enabled so we're fine */
                log_full_errno(ERRNO_IS_NOT_SUPPORTED(errno) ? LOG_DEBUG : LOG_WARNING, errno,
                               "Failed to enable hardware watchdog, ignoring: %m");
                if (!ERRNO_IS_NOT_SUPPORTED(errno))
                        return -errno;
        }

        return 0;
}

static int watchdog_read_timeout(void) {
        int sec = 0;

        assert(watchdog_fd >= 0);

        if (ioctl(watchdog_fd, WDIOC_GETTIMEOUT, &sec) < 0)
                return -errno;

        assert(sec > 0);
        watchdog_timeout = sec * USEC_PER_SEC;

        return 0;
}

static int watchdog_set_timeout(void) {
        int sec;

        assert(watchdog_fd >= 0);
        assert(timestamp_is_set(watchdog_timeout));

        sec = saturated_usec_to_sec(watchdog_timeout);

        if (ioctl(watchdog_fd, WDIOC_SETTIMEOUT, &sec) < 0)
                return -errno;

        assert(sec > 0); /* buggy driver ? */
        watchdog_timeout = sec * USEC_PER_SEC;

        return 0;
}

static int watchdog_read_pretimeout(void) {
        int sec = 0;

        assert(watchdog_fd >= 0);

        if (ioctl(watchdog_fd, WDIOC_GETPRETIMEOUT, &sec) < 0) {
                watchdog_pretimeout = 0;
                return log_full_errno(ERRNO_IS_NOT_SUPPORTED(errno) ? LOG_DEBUG : LOG_WARNING, errno, "Failed to get pretimeout value, ignoring: %m");
        }

        watchdog_pretimeout = sec * USEC_PER_SEC;

        return 0;
}

static int watchdog_set_pretimeout(void) {
        int sec;

        assert(watchdog_fd >= 0);
        assert(watchdog_pretimeout != USEC_INFINITY);

        sec = saturated_usec_to_sec(watchdog_pretimeout);

        if (ioctl(watchdog_fd, WDIOC_SETPRETIMEOUT, &sec) < 0) {
                watchdog_pretimeout = 0;

                if (ERRNO_IS_NOT_SUPPORTED(errno)) {
                        log_info("Watchdog does not support pretimeouts.");
                        return 0;
                }

                return log_error_errno(errno, "Failed to set pretimeout to %s: %m", FORMAT_TIMESPAN(sec, USEC_PER_SEC));
        }

        /* The set ioctl does not return the actual value set so get it now. */
        (void) watchdog_read_pretimeout();

        return 0;
}

usec_t watchdog_get_last_ping(clockid_t clock) {
        return map_clock_usec(watchdog_last_ping, CLOCK_BOOTTIME, clock);
}

static int watchdog_ping_now(void) {
        assert(watchdog_fd >= 0);

        if (ioctl(watchdog_fd, WDIOC_KEEPALIVE, 0) < 0)
                return log_warning_errno(errno, "Failed to ping hardware watchdog, ignoring: %m");

        watchdog_last_ping = now(CLOCK_BOOTTIME);

        return 0;
}

static int update_pretimeout(void) {
        _cleanup_free_ char *governor = NULL;
        int r, t_sec, pt_sec;

        if (watchdog_fd < 0)
                return 0;

        if (watchdog_timeout == USEC_INFINITY || watchdog_pretimeout == USEC_INFINITY)
                return 0;

        if (!watchdog_supports_pretimeout && watchdog_pretimeout == 0)
                return 0; /* Nothing to do */

        /* The configuration changed, do not assume it can still work, as the module(s)
         * might have been unloaded. */
        watchdog_supports_pretimeout = false;

        /* Update the pretimeout governor as well */
        (void) set_pretimeout_governor(watchdog_pretimeout_governor);

        r = get_pretimeout_governor(&governor);
        if (r < 0)
                return log_warning_errno(r, "Watchdog: failed to read pretimeout governor: %m");
        if (isempty(governor))
                return log_warning_errno(SYNTHETIC_ERRNO(EINVAL),
                                         "Watchdog: no pretimeout governor detected - is the required kernel module loaded?");

        /* If we have a pretimeout governor, then pretimeout is supported. Without a governor
         * pretimeout does not work at all.
         * Note that this might require a kernel module that is not autoloaded, so we don't
         * cache this, but we check every time the configuration changes. */
        watchdog_supports_pretimeout = true;

        /* Determine if the pretimeout is valid for the current watchdog timeout. */
        t_sec = saturated_usec_to_sec(watchdog_timeout);
        pt_sec = saturated_usec_to_sec(watchdog_pretimeout);
        if (pt_sec >= t_sec) {
                r = log_error_errno(SYNTHETIC_ERRNO(EINVAL),
                                    "Cannot set watchdog pretimeout to %is (%s watchdog timeout of %is)",
                                    pt_sec, pt_sec == t_sec ? "same as" : "longer than", t_sec);
                (void) watchdog_read_pretimeout();
        } else
                r = watchdog_set_pretimeout();

        if (watchdog_pretimeout == 0)
                log_info("Watchdog pretimeout is disabled.");
        else
                log_info("Watchdog running with a pretimeout of %s with governor '%s'.",
                         FORMAT_TIMESPAN(watchdog_pretimeout, 0),
                         governor);

        return r;
}

static int update_timeout(void) {
        int r;
        usec_t previous_timeout;

        assert(watchdog_timeout > 0);

        if (watchdog_fd < 0)
                return 0;

        previous_timeout = watchdog_timeout;

        if (watchdog_timeout != USEC_INFINITY) {
                r = watchdog_set_timeout();
                if (r < 0) {
                        if (!ERRNO_IS_NOT_SUPPORTED(r))
                                return log_error_errno(r, "Failed to set timeout to %s: %m",
                                                       FORMAT_TIMESPAN(watchdog_timeout, 0));

                        log_info("Modifying watchdog timeout is not supported, reusing the programmed timeout.");
                        watchdog_timeout = USEC_INFINITY;
                }
        }

        if (watchdog_timeout == USEC_INFINITY) {
                r = watchdog_read_timeout();
                if (r < 0) {
                        if (!ERRNO_IS_NOT_SUPPORTED(r))
                                return log_error_errno(r, "Failed to query watchdog HW timeout: %m");
                        log_info("Reading watchdog timeout is not supported, reusing the configured timeout.");
                        watchdog_timeout = previous_timeout;
                }
        }

        /* If the watchdog timeout was changed, the pretimeout could have been
         * changed as well by the driver or the kernel so we need to update the
         * pretimeout now. Or if the watchdog is being configured for the first
         * time, we want to configure the pretimeout before it is enabled. */
        (void) update_pretimeout();

        r = watchdog_set_enable(true);
        if (r < 0)
                return r;

        log_info("Watchdog running with a timeout of %s.", FORMAT_TIMESPAN(watchdog_timeout, 0));

        return watchdog_ping_now();
}

static int open_watchdog(void) {
        struct watchdog_info ident;
        char **try_order;
        int r;

        if (watchdog_fd >= 0)
                return 0;

        /* Let's prefer new-style /dev/watchdog0 (i.e. kernel 3.5+) over classic /dev/watchdog. The former
         * has the benefit that we can easily find the matching directory in sysfs from it, as the relevant
         * sysfs attributes can only be found via /sys/dev/char/<major>:<minor> if the new-style device
         * major/minor is used, not the old-style. */
        try_order = !watchdog_device || PATH_IN_SET(watchdog_device, "/dev/watchdog", "/dev/watchdog0") ?
                STRV_MAKE("/dev/watchdog0", "/dev/watchdog") : STRV_MAKE(watchdog_device);

        STRV_FOREACH(wd, try_order) {
                watchdog_fd = open(*wd, O_WRONLY|O_CLOEXEC);
                if (watchdog_fd >= 0) {
                        r = free_and_strdup(&watchdog_device, *wd);
                        if (r < 0)
                                return log_oom_debug();

                        break;
                }

                if (errno != ENOENT)
                        return log_debug_errno(errno, "Failed to open watchdog device %s: %m", *wd);
        }

        if (watchdog_fd < 0)
                return log_debug_errno(SYNTHETIC_ERRNO(ENOENT), "Failed to open watchdog device %s: %m", watchdog_device ?: "auto");

        if (ioctl(watchdog_fd, WDIOC_GETSUPPORT, &ident) < 0)
                log_debug_errno(errno, "Hardware watchdog %s does not support WDIOC_GETSUPPORT ioctl, ignoring: %m", watchdog_device);
        else
                log_info("Using hardware watchdog '%s', version %x, device %s",
                         ident.identity,
                         ident.firmware_version,
                         watchdog_device);

        r = update_timeout();
        if (r < 0)
                watchdog_close(true);

        return r;
}

const char *watchdog_get_device(void) {
        return watchdog_device;
}

int watchdog_set_device(const char *path) {
        int r;

        r = free_and_strdup(&watchdog_device, path);
        if (r > 0) /* watchdog_device changed */
                watchdog_fd = safe_close(watchdog_fd);

        return r;
}

int watchdog_setup(usec_t timeout) {
        usec_t previous_timeout;
        int r;

        /* timeout=0 closes the device whereas passing timeout=USEC_INFINITY opens it (if needed)
         * without configuring any particular timeout and thus reuses the programmed value (therefore
         * it's a nop if the device is already opened). */

        if (timeout == 0) {
                watchdog_close(true);
                return 0;
        }

        /* Let's shortcut duplicated requests */
        if (watchdog_fd >= 0 && (timeout == watchdog_timeout || timeout == USEC_INFINITY))
                return 0;

        /* Initialize the watchdog timeout with the caller value. This value is going to be updated by
         * update_timeout() with the closest value supported by the driver */
        previous_timeout = watchdog_timeout;
        watchdog_timeout = timeout;

        if (watchdog_fd < 0)
                return open_watchdog();

        r = update_timeout();
        if (r < 0)
                watchdog_timeout = previous_timeout;

        return r;
}

int watchdog_setup_pretimeout(usec_t timeout) {
        /* timeout=0 disables the pretimeout whereas timeout=USEC_INFINITY is a nop. */
        if ((watchdog_fd >= 0 && timeout == watchdog_pretimeout) || timeout == USEC_INFINITY)
                return 0;

        /* Initialize the watchdog timeout with the caller value. This value is
         * going to be updated by update_pretimeout() with the running value,
         * even if it fails to update the timeout. */
        watchdog_pretimeout = timeout;

        return update_pretimeout();
}

int watchdog_setup_pretimeout_governor(const char *governor) {
        if (free_and_strdup(&watchdog_pretimeout_governor, governor) < 0)
                return -ENOMEM;

        return set_pretimeout_governor(watchdog_pretimeout_governor);
}

static usec_t calc_timeout(void) {
        /* Calculate the effective timeout which accounts for the watchdog
         * pretimeout if configured and supported. */
        if (watchdog_supports_pretimeout && timestamp_is_set(watchdog_pretimeout) && watchdog_timeout >= watchdog_pretimeout)
                return watchdog_timeout - watchdog_pretimeout;
        else
                return watchdog_timeout;
}

usec_t watchdog_runtime_wait(void) {
        usec_t timeout = calc_timeout();
        if (!timestamp_is_set(timeout))
                return USEC_INFINITY;

        /* Sleep half the watchdog timeout since the last successful ping at most */
        if (timestamp_is_set(watchdog_last_ping)) {
                usec_t ntime = now(CLOCK_BOOTTIME);

                assert(ntime >= watchdog_last_ping);
                return usec_sub_unsigned(watchdog_last_ping + (timeout / 2), ntime);
        }

        return timeout / 2;
}

int watchdog_ping(void) {
        usec_t ntime, timeout;

        if (watchdog_timeout == 0)
                return 0;

        if (watchdog_fd < 0)
                /* open_watchdog() will automatically ping the device for us if necessary */
                return open_watchdog();

        ntime = now(CLOCK_BOOTTIME);
        timeout = calc_timeout();

        /* Never ping earlier than watchdog_timeout/4 and try to ping
         * by watchdog_timeout/2 plus scheduling latencies at the latest */
        if (timestamp_is_set(watchdog_last_ping)) {
                assert(ntime >= watchdog_last_ping);
                if ((ntime - watchdog_last_ping) < (timeout / 4))
                        return 0;
        }

        return watchdog_ping_now();
}

void watchdog_close(bool disarm) {

        /* Once closed, pinging the device becomes a NOP and we request a new
         * call to watchdog_setup() to open the device again. */
        watchdog_timeout = 0;

        if (watchdog_fd < 0)
                return;

        if (disarm) {
                (void) watchdog_set_enable(false);

                /* To be sure, use magic close logic, too */
                for (;;) {
                        static const char v = 'V';

                        if (write(watchdog_fd, &v, 1) > 0)
                                break;

                        if (errno != EINTR) {
                                log_warning_errno(errno, "Failed to disarm watchdog timer, ignoring: %m");
                                break;
                        }
                }
        }

        watchdog_fd = safe_close(watchdog_fd);
}