2 * Copyright (c) 2009 Isilon Inc http://www.isilon.com/
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30 * @ingroup failpoint_private
33 * @defgroup failpoint fail(9) Facility
35 * Failpoints allow for injecting fake errors into running code on the fly,
36 * without modifying code or recompiling with flags. Failpoints are always
37 * present, and are very efficient when disabled. Failpoints are described
41 * @defgroup failpoint_private Private fail(9) Implementation functions
43 * Private implementations for the actual failpoint code.
48 * @addtogroup failpoint_private
52 #include <sys/cdefs.h>
53 __FBSDID("$FreeBSD$");
55 #include <sys/errno.h>
57 #include <sys/kernel.h>
58 #include <sys/libkern.h>
60 #include <sys/malloc.h>
61 #include <sys/mutex.h>
64 #include <machine/stdarg.h>
66 #ifdef ILOG_DEFINE_FOR_FILE
67 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
70 MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
71 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
72 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
74 static struct mtx g_fp_mtx;
75 MTX_SYSINIT(g_fp_mtx, &g_fp_mtx, "fail point mtx", MTX_DEF);
76 #define FP_LOCK() mtx_lock(&g_fp_mtx)
77 #define FP_UNLOCK() mtx_unlock(&g_fp_mtx)
80 fail_point_sleep(struct fail_point *fp, struct fail_point_entry *ent,
81 int msecs, enum fail_point_return_code *pret)
83 /* convert from millisecs to ticks, rounding up */
84 int timo = ((msecs * hz) + 999) / 1000;
87 if (fp->fp_sleep_fn == NULL) {
88 msleep(fp, &g_fp_mtx, PWAIT, "failpt", timo);
90 timeout(fp->fp_sleep_fn, fp->fp_sleep_arg, timo);
91 *pret = FAIL_POINT_RC_QUEUED;
98 * Defines stating the equivalent of probablilty one (100%)
101 PROB_MAX = 1000000, /* probability between zero and this number */
102 PROB_DIGITS = 6, /* number of zero's in above number */
105 static const char *fail_type_strings[] = {
114 static char *parse_fail_point(struct fail_point_entries *, char *);
115 static char *parse_term(struct fail_point_entries *, char *);
116 static char *parse_number(int *out_units, int *out_decimal, char *);
117 static char *parse_type(struct fail_point_entry *, char *);
118 static void free_entry(struct fail_point_entries *, struct fail_point_entry *);
119 static void clear_entries(struct fail_point_entries *);
122 * Initialize a fail_point. The name is formed in a printf-like fashion
123 * from "fmt" and subsequent arguments. This function is generally used
124 * for custom failpoints located at odd places in the sysctl tree, and is
125 * not explicitly needed for standard in-line-declared failpoints.
130 fail_point_init(struct fail_point *fp, const char *fmt, ...)
136 TAILQ_INIT(&fp->fp_entries);
139 /* Figure out the size of the name. */
141 n = vsnprintf(NULL, 0, fmt, ap);
144 /* Allocate the name and fill it in. */
145 name = fp_malloc(n + 1, M_WAITOK);
148 vsnprintf(name, n + 1, fmt, ap);
152 fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
153 fp->fp_sleep_fn = NULL;
154 fp->fp_sleep_arg = NULL;
158 * Free the resources held by a fail_point.
163 fail_point_destroy(struct fail_point *fp)
165 struct fail_point_entry *ent;
167 if (fp->fp_flags & FAIL_POINT_DYNAMIC_NAME && fp->fp_name != NULL) {
168 fp_free((void *)(intptr_t)fp->fp_name);
173 while (!TAILQ_EMPTY(&fp->fp_entries)) {
174 ent = TAILQ_FIRST(&fp->fp_entries);
175 TAILQ_REMOVE(&fp->fp_entries, ent, fe_entries);
181 * This does the real work of evaluating a fail point. If the fail point tells
182 * us to return a value, this function returns 1 and fills in 'return_value'
183 * (return_value is allowed to be null). If the fail point tells us to panic,
184 * we never return. Otherwise we just return 0 after doing some work, which
185 * means "keep going".
187 enum fail_point_return_code
188 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
190 enum fail_point_return_code ret = FAIL_POINT_RC_CONTINUE;
191 struct fail_point_entry *ent, *next;
196 ent = TAILQ_FIRST(&fp->fp_entries);
198 int cont = 0; /* don't continue by default */
199 next = TAILQ_NEXT(ent, fe_entries);
201 if (ent->fe_prob < PROB_MAX &&
202 ent->fe_prob < random() % PROB_MAX) {
207 switch (ent->fe_type) {
208 case FAIL_POINT_PANIC:
209 panic("fail point %s panicking", fp->fp_name);
212 case FAIL_POINT_RETURN:
214 *return_value = ent->fe_arg;
215 ret = FAIL_POINT_RC_RETURN;
218 case FAIL_POINT_BREAK:
219 printf("fail point %s breaking to debugger\n", fp->fp_name);
223 case FAIL_POINT_PRINT:
224 printf("fail point %s executing\n", fp->fp_name);
228 case FAIL_POINT_SLEEP:
230 * Free the entry now if necessary, since
231 * we're about to drop the mutex and sleep.
234 if (ent->fe_count > 0 && --ent->fe_count == 0) {
235 free_entry(&fp->fp_entries, ent);
240 fail_point_sleep(fp, ent, msecs, &ret);
247 if (ent && ent->fe_count > 0 && --ent->fe_count == 0)
248 free_entry(&fp->fp_entries, ent);
257 /* Get rid of "off"s at the end. */
258 while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
259 ent->fe_type == FAIL_POINT_OFF)
260 free_entry(&fp->fp_entries, ent);
268 * Translate internal fail_point structure into human-readable text.
271 fail_point_get(struct fail_point *fp, struct sbuf *sb)
273 struct fail_point_entry *ent;
277 TAILQ_FOREACH(ent, &fp->fp_entries, fe_entries) {
278 if (ent->fe_prob < PROB_MAX) {
279 int decimal = ent->fe_prob % (PROB_MAX / 100);
280 int units = ent->fe_prob / (PROB_MAX / 100);
281 sbuf_printf(sb, "%d", units);
283 int digits = PROB_DIGITS - 2;
284 while (!(decimal % 10)) {
288 sbuf_printf(sb, ".%0*d", digits, decimal);
290 sbuf_printf(sb, "%%");
292 if (ent->fe_count > 0)
293 sbuf_printf(sb, "%d*", ent->fe_count);
294 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type]);
296 sbuf_printf(sb, "(%d)", ent->fe_arg);
297 if (TAILQ_NEXT(ent, fe_entries))
298 sbuf_printf(sb, "->");
300 if (TAILQ_EMPTY(&fp->fp_entries))
301 sbuf_printf(sb, "off");
307 * Set an internal fail_point structure from a human-readable failpoint string
308 * in a lock-safe manner.
311 fail_point_set(struct fail_point *fp, char *buf)
314 struct fail_point_entry *ent, *ent_next;
315 struct fail_point_entries new_entries;
317 /* Parse new entries. */
318 TAILQ_INIT(&new_entries);
319 if (!parse_fail_point(&new_entries, buf)) {
320 clear_entries(&new_entries);
327 /* Move new entries in. */
328 TAILQ_SWAP(&fp->fp_entries, &new_entries, fail_point_entry, fe_entries);
329 clear_entries(&new_entries);
331 /* Get rid of useless zero probability entries. */
332 TAILQ_FOREACH_SAFE(ent, &fp->fp_entries, fe_entries, ent_next) {
333 if (ent->fe_prob == 0)
334 free_entry(&fp->fp_entries, ent);
337 /* Get rid of "off"s at the end. */
338 while ((ent = TAILQ_LAST(&fp->fp_entries, fail_point_entries)) &&
339 ent->fe_type == FAIL_POINT_OFF)
340 free_entry(&fp->fp_entries, ent);
347 IWARNING("Failed to set %s (%s) to %s",
348 fp->fp_name, fp->fp_location, buf);
350 INOTICE("Set %s (%s) to %s",
351 fp->fp_name, fp->fp_location, buf);
352 #endif /* IWARNING */
357 #define MAX_FAIL_POINT_BUF 1023
360 * Handle kernel failpoint set/get.
363 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
365 struct fail_point *fp = arg1;
371 sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
372 fail_point_get(fp, &sb);
375 error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
379 if (!error && req->newptr) {
380 if (req->newlen > MAX_FAIL_POINT_BUF) {
385 buf = fp_malloc(req->newlen + 1, M_WAITOK);
387 error = SYSCTL_IN(req, buf, req->newlen);
390 buf[req->newlen] = '\0';
392 error = fail_point_set(fp, buf);
402 * Internal helper function to translate a human-readable failpoint string
403 * into a internally-parsable fail_point structure.
406 parse_fail_point(struct fail_point_entries *ents, char *p)
409 * <term> ( "->" <term> )*
411 if (!(p = parse_term(ents, p)))
414 if (p[0] != '-' || p[1] != '>' || !(p = parse_term(ents, p+2)))
420 * Internal helper function to parse an individual term from a failpoint.
423 parse_term(struct fail_point_entries *ents, char *p)
425 struct fail_point_entry *ent;
427 ent = fp_malloc(sizeof *ent, M_WAITOK | M_ZERO);
428 ent->fe_prob = PROB_MAX;
429 TAILQ_INSERT_TAIL(ents, ent, fe_entries);
433 * ( (<float> "%") | (<integer> "*" ) )*
435 * [ "(" <integer> ")" ]
438 /* ( (<float> "%") | (<integer> "*" ) )* */
439 while (('0' <= *p && *p <= '9') || *p == '.') {
442 if (!(p = parse_number(&units, &decimal, p)))
446 if (units > 100) /* prevent overflow early */
448 ent->fe_prob = units * (PROB_MAX / 100) + decimal;
449 if (ent->fe_prob > PROB_MAX)
450 ent->fe_prob = PROB_MAX;
452 } else if (*p == '*') {
453 if (!units || decimal)
455 ent->fe_count = units;
465 if (!(p = parse_type(ent, p)))
470 /* [ "(" <integer> ")" ] */
474 if (('0' <= *p && *p <= '9') || *p == '-')
475 ent->fe_arg = strtol(p, &p, 0);
485 * Internal helper function to parse a numeric for a failpoint term.
488 parse_number(int *out_units, int *out_decimal, char *p)
494 * <integer> [ "." <integer> ] |
500 *out_units = strtol(p, &p, 10);
501 if (p == old_p && *p != '.')
504 /* fractional part */
509 while ('0' <= *p && *p <= '9') {
510 int digit = *p - '0';
511 if (digits < PROB_DIGITS - 2)
512 *out_decimal = *out_decimal * 10 + digit;
513 else if (digits == PROB_DIGITS - 2 && digit >= 5)
518 if (!digits) /* need at least one digit after '.' */
520 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
524 return p; /* success */
528 * Internal helper function to parse an individual type for a failpoint term.
531 parse_type(struct fail_point_entry *ent, char *beg)
533 enum fail_point_t type;
535 while ('a' <= *end && *end <= 'z')
539 for (type = FAIL_POINT_OFF; type != FAIL_POINT_INVALID; type++) {
540 const char *p = fail_type_strings[type];
542 while (q < end && *p++ == *q++);
543 if (q == end && *p == '\0') {
552 * Internal helper function to free an individual failpoint term.
555 free_entry(struct fail_point_entries *ents, struct fail_point_entry *ent)
557 TAILQ_REMOVE(ents, ent, fe_entries);
562 * Internal helper function to clear out all failpoint terms for a single
566 clear_entries(struct fail_point_entries *ents)
568 struct fail_point_entry *ent, *ent_next;
569 TAILQ_FOREACH_SAFE(ent, ents, fe_entries, ent_next)
574 /* The fail point sysctl tree. */
575 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");