The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_fail.c

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    1 /*-
    2  * Copyright (c) 2009 Isilon Inc http://www.isilon.com/
    3  *
    4  * Redistribution and use in source and binary forms, with or without
    5  * modification, are permitted provided that the following conditions
    6  * are met:
    7  * 1. Redistributions of source code must retain the above copyright
    8  *    notice, this list of conditions and the following disclaimer.
    9  * 2. Redistributions in binary form must reproduce the above copyright
   10  *    notice, this list of conditions and the following disclaimer in the
   11  *    documentation and/or other materials provided with the distribution.
   12  *
   13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   14  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   16  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   17  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   18  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   19  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   20  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   21  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   22  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   23  * SUCH DAMAGE.
   24  */
   25 /**
   26  * @file
   27  *
   28  * fail(9) Facility.
   29  *
   30  * @ingroup failpoint_private
   31  */
   32 /**
   33  * @defgroup failpoint fail(9) Facility
   34  *
   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
   38  * in man fail(9).
   39  */
   40 /**
   41  * @defgroup failpoint_private Private fail(9) Implementation functions
   42  *
   43  * Private implementations for the actual failpoint code.
   44  *
   45  * @ingroup failpoint
   46  */
   47 /**
   48  * @addtogroup failpoint_private
   49  * @{
   50  */
   51 
   52 #include <sys/cdefs.h>
   53 __FBSDID("$FreeBSD: releng/11.0/sys/kern/kern_fail.c 301727 2016-06-09 13:17:08Z markj $");
   54 
   55 #include "opt_stack.h"
   56 
   57 #include <sys/ctype.h>
   58 #include <sys/errno.h>
   59 #include <sys/fail.h>
   60 #include <sys/kernel.h>
   61 #include <sys/libkern.h>
   62 #include <sys/limits.h>
   63 #include <sys/lock.h>
   64 #include <sys/malloc.h>
   65 #include <sys/mutex.h>
   66 #include <sys/proc.h>
   67 #include <sys/sbuf.h>
   68 #include <sys/sleepqueue.h>
   69 #include <sys/sx.h>
   70 #include <sys/sysctl.h>
   71 #include <sys/types.h>
   72 
   73 #include <machine/atomic.h>
   74 #include <machine/stdarg.h>
   75 
   76 #ifdef ILOG_DEFINE_FOR_FILE
   77 ILOG_DEFINE_FOR_FILE(L_ISI_FAIL_POINT, L_ILOG, fail_point);
   78 #endif
   79 
   80 static MALLOC_DEFINE(M_FAIL_POINT, "Fail Points", "fail points system");
   81 #define fp_free(ptr) free(ptr, M_FAIL_POINT)
   82 #define fp_malloc(size, flags) malloc((size), M_FAIL_POINT, (flags))
   83 #define fs_free(ptr) fp_free(ptr)
   84 #define fs_malloc() fp_malloc(sizeof(struct fail_point_setting), \
   85     M_WAITOK | M_ZERO)
   86 
   87 /**
   88  * These define the wchans that are used for sleeping, pausing respectively.
   89  * They are chosen arbitrarily but need to be distinct to the failpoint and
   90  * the sleep/pause distinction.
   91  */
   92 #define FP_SLEEP_CHANNEL(fp) (void*)(fp)
   93 #define FP_PAUSE_CHANNEL(fp) __DEVOLATILE(void*, &fp->fp_setting)
   94 
   95 /**
   96  * Don't allow more than this many entries in a fail point set by sysctl.
   97  * The 99.99...% case is to have 1 entry.  I can't imagine having this many
   98  * entries, so it should not limit us.  Saves on re-mallocs while holding
   99  * a non-sleepable lock.
  100  */
  101 #define FP_MAX_ENTRY_COUNT 20
  102 
  103 /* Used to drain sbufs to the sysctl output */
  104 int fail_sysctl_drain_func(void *, const char *, int);
  105 
  106 /* Head of tailq of struct fail_point_entry */
  107 TAILQ_HEAD(fail_point_entry_queue, fail_point_entry);
  108 
  109 /**
  110  * fp entries garbage list; outstanding entries are cleaned up in the
  111  * garbage collector
  112  */
  113 STAILQ_HEAD(fail_point_setting_garbage, fail_point_setting);
  114 static struct fail_point_setting_garbage fp_setting_garbage =
  115         STAILQ_HEAD_INITIALIZER(fp_setting_garbage);
  116 static struct mtx mtx_garbage_list;
  117 MTX_SYSINIT(mtx_garbage_list, &mtx_garbage_list, "fail point garbage mtx",
  118         MTX_SPIN);
  119 
  120 static struct sx sx_fp_set;
  121 SX_SYSINIT(sx_fp_set, &sx_fp_set, "fail point set sx");
  122 
  123 /**
  124  * Failpoint types.
  125  * Don't change these without changing fail_type_strings in fail.c.
  126  * @ingroup failpoint_private
  127  */
  128 enum fail_point_t {
  129         FAIL_POINT_OFF,         /**< don't fail */
  130         FAIL_POINT_PANIC,       /**< panic */
  131         FAIL_POINT_RETURN,      /**< return an errorcode */
  132         FAIL_POINT_BREAK,       /**< break into the debugger */
  133         FAIL_POINT_PRINT,       /**< print a message */
  134         FAIL_POINT_SLEEP,       /**< sleep for some msecs */
  135         FAIL_POINT_PAUSE,       /**< sleep until failpoint is set to off */
  136         FAIL_POINT_YIELD,       /**< yield the cpu */
  137         FAIL_POINT_DELAY,       /**< busy wait the cpu */
  138         FAIL_POINT_NUMTYPES,
  139         FAIL_POINT_INVALID = -1
  140 };
  141 
  142 static struct {
  143         const char *name;
  144         int     nmlen;
  145 } fail_type_strings[] = {
  146 #define FP_TYPE_NM_LEN(s)       { s, sizeof(s) - 1 }
  147         [FAIL_POINT_OFF] =      FP_TYPE_NM_LEN("off"),
  148         [FAIL_POINT_PANIC] =    FP_TYPE_NM_LEN("panic"),
  149         [FAIL_POINT_RETURN] =   FP_TYPE_NM_LEN("return"),
  150         [FAIL_POINT_BREAK] =    FP_TYPE_NM_LEN("break"),
  151         [FAIL_POINT_PRINT] =    FP_TYPE_NM_LEN("print"),
  152         [FAIL_POINT_SLEEP] =    FP_TYPE_NM_LEN("sleep"),
  153         [FAIL_POINT_PAUSE] =    FP_TYPE_NM_LEN("pause"),
  154         [FAIL_POINT_YIELD] =    FP_TYPE_NM_LEN("yield"),
  155         [FAIL_POINT_DELAY] =    FP_TYPE_NM_LEN("delay"),
  156 };
  157 
  158 #define FE_COUNT_UNTRACKED (INT_MIN)
  159 
  160 /**
  161  * Internal structure tracking a single term of a complete failpoint.
  162  * @ingroup failpoint_private
  163  */
  164 struct fail_point_entry {
  165         volatile bool   fe_stale;
  166         enum fail_point_t       fe_type;        /**< type of entry */
  167         int             fe_arg;         /**< argument to type (e.g. return value) */
  168         int             fe_prob;        /**< likelihood of firing in millionths */
  169         int32_t         fe_count;       /**< number of times to fire, -1 means infinite */
  170         pid_t           fe_pid;         /**< only fail for this process */
  171         struct fail_point       *fe_parent;     /**< backpointer to fp */
  172         TAILQ_ENTRY(fail_point_entry)   fe_entries; /**< next entry ptr */
  173 };
  174 
  175 struct fail_point_setting {
  176         STAILQ_ENTRY(fail_point_setting) fs_garbage_link;
  177         struct fail_point_entry_queue fp_entry_queue;
  178         struct fail_point * fs_parent;
  179         struct mtx feq_mtx; /* Gives fail_point_pause something to do.  */
  180 };
  181 
  182 /**
  183  * Defines stating the equivalent of probablilty one (100%)
  184  */
  185 enum {
  186         PROB_MAX = 1000000,     /* probability between zero and this number */
  187         PROB_DIGITS = 6         /* number of zero's in above number */
  188 };
  189 
  190 /* Get a ref on an fp's fp_setting */
  191 static inline struct fail_point_setting *fail_point_setting_get_ref(
  192         struct fail_point *fp);
  193 /* Release a ref on an fp_setting */
  194 static inline void fail_point_setting_release_ref(struct fail_point *fp);
  195 /* Allocate and initialize a struct fail_point_setting */
  196 static struct fail_point_setting *fail_point_setting_new(struct
  197         fail_point *);
  198 /* Free a struct fail_point_setting */
  199 static void fail_point_setting_destroy(struct fail_point_setting *fp_setting);
  200 /* Allocate and initialize a struct fail_point_entry */
  201 static struct fail_point_entry *fail_point_entry_new(struct
  202         fail_point_setting *);
  203 /* Free a struct fail_point_entry */
  204 static void fail_point_entry_destroy(struct fail_point_entry *fp_entry);
  205 /* Append fp setting to garbage list */
  206 static inline void fail_point_setting_garbage_append(
  207         struct fail_point_setting *fp_setting);
  208 /* Swap fp's setting with fp_setting_new */
  209 static inline struct fail_point_setting *
  210         fail_point_swap_settings(struct fail_point *fp,
  211         struct fail_point_setting *fp_setting_new);
  212 /* Free up any zero-ref setting in the garbage queue */
  213 static void fail_point_garbage_collect(void);
  214 /* If this fail point's setting are empty, then swap it out to NULL. */
  215 static inline void fail_point_eval_swap_out(struct fail_point *fp,
  216         struct fail_point_setting *fp_setting);
  217 
  218 bool
  219 fail_point_is_off(struct fail_point *fp)
  220 {
  221         bool return_val;
  222         struct fail_point_setting *fp_setting;
  223         struct fail_point_entry *ent;
  224 
  225         return_val = true;
  226 
  227         fp_setting = fail_point_setting_get_ref(fp);
  228         if (fp_setting != NULL) {
  229                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue,
  230                     fe_entries) {
  231                         if (!ent->fe_stale) {
  232                                 return_val = false;
  233                                 break;
  234                         }
  235                 }
  236         }
  237         fail_point_setting_release_ref(fp);
  238 
  239         return (return_val);
  240 }
  241 
  242 /* Allocate and initialize a struct fail_point_setting */
  243 static struct fail_point_setting *
  244 fail_point_setting_new(struct fail_point *fp)
  245 {
  246         struct fail_point_setting *fs_new;
  247 
  248         fs_new = fs_malloc();
  249         fs_new->fs_parent = fp;
  250         TAILQ_INIT(&fs_new->fp_entry_queue);
  251         mtx_init(&fs_new->feq_mtx, "fail point entries", NULL, MTX_SPIN);
  252 
  253         fail_point_setting_garbage_append(fs_new);
  254 
  255         return (fs_new);
  256 }
  257 
  258 /* Free a struct fail_point_setting */
  259 static void
  260 fail_point_setting_destroy(struct fail_point_setting *fp_setting)
  261 {
  262         struct fail_point_entry *ent;
  263 
  264         while (!TAILQ_EMPTY(&fp_setting->fp_entry_queue)) {
  265                 ent = TAILQ_FIRST(&fp_setting->fp_entry_queue);
  266                 TAILQ_REMOVE(&fp_setting->fp_entry_queue, ent, fe_entries);
  267                 fail_point_entry_destroy(ent);
  268         }
  269 
  270         fs_free(fp_setting);
  271 }
  272 
  273 /* Allocate and initialize a struct fail_point_entry */
  274 static struct fail_point_entry *
  275 fail_point_entry_new(struct fail_point_setting *fp_setting)
  276 {
  277         struct fail_point_entry *fp_entry;
  278 
  279         fp_entry = fp_malloc(sizeof(struct fail_point_entry),
  280                 M_WAITOK | M_ZERO);
  281         fp_entry->fe_parent = fp_setting->fs_parent;
  282         fp_entry->fe_prob = PROB_MAX;
  283         fp_entry->fe_pid = NO_PID;
  284         fp_entry->fe_count = FE_COUNT_UNTRACKED;
  285         TAILQ_INSERT_TAIL(&fp_setting->fp_entry_queue, fp_entry,
  286                 fe_entries);
  287 
  288         return (fp_entry);
  289 }
  290 
  291 /* Free a struct fail_point_entry */
  292 static void
  293 fail_point_entry_destroy(struct fail_point_entry *fp_entry)
  294 {
  295 
  296         fp_free(fp_entry);
  297 }
  298 
  299 /* Get a ref on an fp's fp_setting */
  300 static inline struct fail_point_setting *
  301 fail_point_setting_get_ref(struct fail_point *fp)
  302 {
  303         struct fail_point_setting *fp_setting;
  304 
  305         /* Invariant: if we have a ref, our pointer to fp_setting is safe */
  306         atomic_add_acq_32(&fp->fp_ref_cnt, 1);
  307         fp_setting = fp->fp_setting;
  308 
  309         return (fp_setting);
  310 }
  311 
  312 /* Release a ref on an fp_setting */
  313 static inline void
  314 fail_point_setting_release_ref(struct fail_point *fp)
  315 {
  316 
  317         KASSERT(&fp->fp_ref_cnt > 0, ("Attempting to deref w/no refs"));
  318         atomic_subtract_rel_32(&fp->fp_ref_cnt, 1);
  319 }
  320 
  321 /* Append fp entries to fp garbage list */
  322 static inline void
  323 fail_point_setting_garbage_append(struct fail_point_setting *fp_setting)
  324 {
  325 
  326         mtx_lock_spin(&mtx_garbage_list);
  327         STAILQ_INSERT_TAIL(&fp_setting_garbage, fp_setting,
  328                 fs_garbage_link);
  329         mtx_unlock_spin(&mtx_garbage_list);
  330 }
  331 
  332 /* Swap fp's entries with fp_setting_new */
  333 static struct fail_point_setting *
  334 fail_point_swap_settings(struct fail_point *fp,
  335         struct fail_point_setting *fp_setting_new)
  336 {
  337         struct fail_point_setting *fp_setting_old;
  338 
  339         fp_setting_old = fp->fp_setting;
  340         fp->fp_setting = fp_setting_new;
  341 
  342         return (fp_setting_old);
  343 }
  344 
  345 static inline void
  346 fail_point_eval_swap_out(struct fail_point *fp,
  347         struct fail_point_setting *fp_setting)
  348 {
  349 
  350         /* We may have already been swapped out and replaced; ignore. */
  351         if (fp->fp_setting == fp_setting)
  352                 fail_point_swap_settings(fp, NULL);
  353 }
  354 
  355 /* Free up any zero-ref entries in the garbage queue */
  356 static void
  357 fail_point_garbage_collect(void)
  358 {
  359         struct fail_point_setting *fs_current, *fs_next;
  360         struct fail_point_setting_garbage fp_ents_free_list;
  361 
  362         /**
  363           * We will transfer the entries to free to fp_ents_free_list while holding
  364           * the spin mutex, then free it after we drop the lock. This avoids
  365           * triggering witness due to sleepable mutexes in the memory
  366           * allocator.
  367           */
  368         STAILQ_INIT(&fp_ents_free_list);
  369 
  370         mtx_lock_spin(&mtx_garbage_list);
  371         STAILQ_FOREACH_SAFE(fs_current, &fp_setting_garbage, fs_garbage_link,
  372             fs_next) {
  373                 if (fs_current->fs_parent->fp_setting != fs_current &&
  374                         fs_current->fs_parent->fp_ref_cnt == 0) {
  375                         STAILQ_REMOVE(&fp_setting_garbage, fs_current,
  376                                 fail_point_setting, fs_garbage_link);
  377                         STAILQ_INSERT_HEAD(&fp_ents_free_list, fs_current,
  378                                 fs_garbage_link);
  379                 }
  380         }
  381         mtx_unlock_spin(&mtx_garbage_list);
  382 
  383         STAILQ_FOREACH_SAFE(fs_current, &fp_ents_free_list, fs_garbage_link,
  384                 fs_next)
  385                 fail_point_setting_destroy(fs_current);
  386 }
  387 
  388 /* Drain out all refs from this fail point */
  389 static inline void
  390 fail_point_drain(struct fail_point *fp, int expected_ref)
  391 {
  392         struct fail_point_setting *entries;
  393 
  394         entries = fail_point_swap_settings(fp, NULL);
  395         /**
  396          * We have unpaused all threads; so we will wait no longer
  397          * than the time taken for the longest remaining sleep, or
  398          * the length of time of a long-running code block.
  399          */
  400         while (fp->fp_ref_cnt > expected_ref) {
  401                 wakeup(FP_PAUSE_CHANNEL(fp));
  402                 tsleep(&fp, PWAIT, "fail_point_drain", hz / 100);
  403         }
  404         fail_point_swap_settings(fp, entries);
  405 }
  406 
  407 static inline void
  408 fail_point_pause(struct fail_point *fp, enum fail_point_return_code *pret,
  409         struct mtx *mtx_sleep)
  410 {
  411 
  412         if (fp->fp_pre_sleep_fn)
  413                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
  414 
  415         msleep_spin(FP_PAUSE_CHANNEL(fp), mtx_sleep, "failpt", 0);
  416 
  417         if (fp->fp_post_sleep_fn)
  418                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
  419 }
  420 
  421 static inline void
  422 fail_point_sleep(struct fail_point *fp, int msecs,
  423         enum fail_point_return_code *pret)
  424 {
  425         int timo;
  426 
  427         /* Convert from millisecs to ticks, rounding up */
  428         timo = howmany(msecs * hz, 1000);
  429 
  430         if (timo > 0) {
  431                 if (!(fp->fp_flags & FAIL_POINT_USE_TIMEOUT_PATH)) {
  432                         if (fp->fp_pre_sleep_fn)
  433                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
  434 
  435                         tsleep(FP_SLEEP_CHANNEL(fp), PWAIT, "failpt", timo);
  436 
  437                         if (fp->fp_post_sleep_fn)
  438                                 fp->fp_post_sleep_fn(fp->fp_post_sleep_arg);
  439                 } else {
  440                         if (fp->fp_pre_sleep_fn)
  441                                 fp->fp_pre_sleep_fn(fp->fp_pre_sleep_arg);
  442 
  443                         timeout(fp->fp_post_sleep_fn, fp->fp_post_sleep_arg,
  444                             timo);
  445                         *pret = FAIL_POINT_RC_QUEUED;
  446                 }
  447         }
  448 }
  449 
  450 static char *parse_fail_point(struct fail_point_setting *, char *);
  451 static char *parse_term(struct fail_point_setting *, char *);
  452 static char *parse_number(int *out_units, int *out_decimal, char *);
  453 static char *parse_type(struct fail_point_entry *, char *);
  454 
  455 /**
  456  * Initialize a fail_point.  The name is formed in a printf-like fashion
  457  * from "fmt" and subsequent arguments.  This function is generally used
  458  * for custom failpoints located at odd places in the sysctl tree, and is
  459  * not explicitly needed for standard in-line-declared failpoints.
  460  *
  461  * @ingroup failpoint
  462  */
  463 void
  464 fail_point_init(struct fail_point *fp, const char *fmt, ...)
  465 {
  466         va_list ap;
  467         char *name;
  468         int n;
  469 
  470         fp->fp_setting = NULL;
  471         fp->fp_flags = 0;
  472 
  473         /* Figure out the size of the name. */
  474         va_start(ap, fmt);
  475         n = vsnprintf(NULL, 0, fmt, ap);
  476         va_end(ap);
  477 
  478         /* Allocate the name and fill it in. */
  479         name = fp_malloc(n + 1, M_WAITOK);
  480         if (name != NULL) {
  481                 va_start(ap, fmt);
  482                 vsnprintf(name, n + 1, fmt, ap);
  483                 va_end(ap);
  484         }
  485         fp->fp_name = name;
  486         fp->fp_location = "";
  487         fp->fp_flags |= FAIL_POINT_DYNAMIC_NAME;
  488         fp->fp_pre_sleep_fn = NULL;
  489         fp->fp_pre_sleep_arg = NULL;
  490         fp->fp_post_sleep_fn = NULL;
  491         fp->fp_post_sleep_arg = NULL;
  492 }
  493 
  494 /**
  495  * Free the resources held by a fail_point, and wake any paused threads.
  496  * Thou shalt not allow threads to hit this fail point after you enter this
  497  * function, nor shall you call this multiple times for a given fp.
  498  * @ingroup failpoint
  499  */
  500 void
  501 fail_point_destroy(struct fail_point *fp)
  502 {
  503 
  504         fail_point_drain(fp, 0);
  505 
  506         if ((fp->fp_flags & FAIL_POINT_DYNAMIC_NAME) != 0) {
  507                 fp_free(__DECONST(void *, fp->fp_name));
  508                 fp->fp_name = NULL;
  509         }
  510         fp->fp_flags = 0;
  511 
  512         sx_xlock(&sx_fp_set);
  513         fail_point_garbage_collect();
  514         sx_xunlock(&sx_fp_set);
  515 }
  516 
  517 /**
  518  * This does the real work of evaluating a fail point. If the fail point tells
  519  * us to return a value, this function returns 1 and fills in 'return_value'
  520  * (return_value is allowed to be null). If the fail point tells us to panic,
  521  * we never return. Otherwise we just return 0 after doing some work, which
  522  * means "keep going".
  523  */
  524 enum fail_point_return_code
  525 fail_point_eval_nontrivial(struct fail_point *fp, int *return_value)
  526 {
  527         bool execute = false;
  528         struct fail_point_entry *ent;
  529         struct fail_point_setting *fp_setting;
  530         enum fail_point_return_code ret;
  531         int cont;
  532         int count;
  533         int msecs;
  534         int usecs;
  535 
  536         ret = FAIL_POINT_RC_CONTINUE;
  537         cont = 0; /* don't continue by default */
  538 
  539         fp_setting = fail_point_setting_get_ref(fp);
  540         if (fp_setting == NULL)
  541                 goto abort;
  542 
  543         TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
  544 
  545                 if (ent->fe_stale)
  546                         continue;
  547 
  548                 if (ent->fe_prob < PROB_MAX &&
  549                     ent->fe_prob < random() % PROB_MAX)
  550                         continue;
  551 
  552                 if (ent->fe_pid != NO_PID && ent->fe_pid != curproc->p_pid)
  553                         continue;
  554 
  555                 if (ent->fe_count != FE_COUNT_UNTRACKED) {
  556                         count = ent->fe_count;
  557                         while (count > 0) {
  558                                 if (atomic_cmpset_32(&ent->fe_count, count, count - 1)) {
  559                                         count--;
  560                                         execute = true;
  561                                         break;
  562                                 }
  563                                 count = ent->fe_count;
  564                         }
  565                         if (execute == false)
  566                                 /* We lost the race; consider the entry stale and bail now */
  567                                 continue;
  568                         if (count == 0)
  569                                 ent->fe_stale = true;
  570                 }
  571 
  572                 switch (ent->fe_type) {
  573                 case FAIL_POINT_PANIC:
  574                         panic("fail point %s panicking", fp->fp_name);
  575                         /* NOTREACHED */
  576 
  577                 case FAIL_POINT_RETURN:
  578                         if (return_value != NULL)
  579                                 *return_value = ent->fe_arg;
  580                         ret = FAIL_POINT_RC_RETURN;
  581                         break;
  582 
  583                 case FAIL_POINT_BREAK:
  584                         printf("fail point %s breaking to debugger\n",
  585                                 fp->fp_name);
  586                         breakpoint();
  587                         break;
  588 
  589                 case FAIL_POINT_PRINT:
  590                         printf("fail point %s executing\n", fp->fp_name);
  591                         cont = ent->fe_arg;
  592                         break;
  593 
  594                 case FAIL_POINT_SLEEP:
  595                         msecs = ent->fe_arg;
  596                         if (msecs)
  597                                 fail_point_sleep(fp, msecs, &ret);
  598                         break;
  599 
  600                 case FAIL_POINT_PAUSE:
  601                         /**
  602                          * Pausing is inherently strange with multiple
  603                          * entries given our design.  That is because some
  604                          * entries could be unreachable, for instance in cases like:
  605                          * pause->return. We can never reach the return entry.
  606                          * The sysctl layer actually truncates all entries after
  607                          * a pause for this reason.
  608                          */
  609                         mtx_lock_spin(&fp_setting->feq_mtx);
  610                         fail_point_pause(fp, &ret, &fp_setting->feq_mtx);
  611                         mtx_unlock_spin(&fp_setting->feq_mtx);
  612                         break;
  613 
  614                 case FAIL_POINT_YIELD:
  615                         kern_yield(-1);
  616                         break;
  617 
  618                 case FAIL_POINT_DELAY:
  619                         usecs = ent->fe_arg;
  620                         DELAY(usecs);
  621                         break;
  622 
  623                 default:
  624                         break;
  625                 }
  626 
  627                 if (cont == 0)
  628                         break;
  629         }
  630 
  631         if (fail_point_is_off(fp))
  632                 fail_point_eval_swap_out(fp, fp_setting);
  633 
  634 abort:
  635         fail_point_setting_release_ref(fp);
  636 
  637         return (ret);
  638 }
  639 
  640 /**
  641  * Translate internal fail_point structure into human-readable text.
  642  */
  643 static void
  644 fail_point_get(struct fail_point *fp, struct sbuf *sb,
  645         bool verbose)
  646 {
  647         struct fail_point_entry *ent;
  648         struct fail_point_setting *fp_setting;
  649         struct fail_point_entry *fp_entry_cpy;
  650         int cnt_sleeping;
  651         int idx;
  652         int printed_entry_count;
  653 
  654         cnt_sleeping = 0;
  655         idx = 0;
  656         printed_entry_count = 0;
  657 
  658         fp_entry_cpy = fp_malloc(sizeof(struct fail_point_entry) *
  659                 (FP_MAX_ENTRY_COUNT + 1), M_WAITOK);
  660 
  661         fp_setting = fail_point_setting_get_ref(fp);
  662 
  663         if (fp_setting != NULL) {
  664                 TAILQ_FOREACH(ent, &fp_setting->fp_entry_queue, fe_entries) {
  665                         if (ent->fe_stale)
  666                                 continue;
  667 
  668                         KASSERT(printed_entry_count < FP_MAX_ENTRY_COUNT,
  669                                 ("FP entry list larger than allowed"));
  670 
  671                         fp_entry_cpy[printed_entry_count] = *ent;
  672                         ++printed_entry_count;
  673                 }
  674         }
  675         fail_point_setting_release_ref(fp);
  676 
  677         /* This is our equivalent of a NULL terminator */
  678         fp_entry_cpy[printed_entry_count].fe_type = FAIL_POINT_INVALID;
  679 
  680         while (idx < printed_entry_count) {
  681                 ent = &fp_entry_cpy[idx];
  682                 ++idx;
  683                 if (ent->fe_prob < PROB_MAX) {
  684                         int decimal = ent->fe_prob % (PROB_MAX / 100);
  685                         int units = ent->fe_prob / (PROB_MAX / 100);
  686                         sbuf_printf(sb, "%d", units);
  687                         if (decimal) {
  688                                 int digits = PROB_DIGITS - 2;
  689                                 while (!(decimal % 10)) {
  690                                         digits--;
  691                                         decimal /= 10;
  692                                 }
  693                                 sbuf_printf(sb, ".%0*d", digits, decimal);
  694                         }
  695                         sbuf_printf(sb, "%%");
  696                 }
  697                 if (ent->fe_count >= 0)
  698                         sbuf_printf(sb, "%d*", ent->fe_count);
  699                 sbuf_printf(sb, "%s", fail_type_strings[ent->fe_type].name);
  700                 if (ent->fe_arg)
  701                         sbuf_printf(sb, "(%d)", ent->fe_arg);
  702                 if (ent->fe_pid != NO_PID)
  703                         sbuf_printf(sb, "[pid %d]", ent->fe_pid);
  704                 if (TAILQ_NEXT(ent, fe_entries))
  705                         sbuf_printf(sb, "->");
  706         }
  707         if (!printed_entry_count)
  708                 sbuf_printf(sb, "off");
  709 
  710         fp_free(fp_entry_cpy);
  711         if (verbose) {
  712 #ifdef STACK
  713                 /* Print number of sleeping threads. queue=0 is the argument
  714                  * used by msleep when sending our threads to sleep. */
  715                 sbuf_printf(sb, "\nsleeping_thread_stacks = {\n");
  716                 sleepq_sbuf_print_stacks(sb, FP_SLEEP_CHANNEL(fp), 0,
  717                         &cnt_sleeping);
  718 
  719                 sbuf_printf(sb, "},\n");
  720 #endif
  721                 sbuf_printf(sb, "sleeping_thread_count = %d,\n",
  722                         cnt_sleeping);
  723 
  724 #ifdef STACK
  725                 sbuf_printf(sb, "paused_thread_stacks = {\n");
  726                 sleepq_sbuf_print_stacks(sb, FP_PAUSE_CHANNEL(fp), 0,
  727                         &cnt_sleeping);
  728 
  729                 sbuf_printf(sb, "},\n");
  730 #endif
  731                 sbuf_printf(sb, "paused_thread_count = %d\n",
  732                         cnt_sleeping);
  733         }
  734 }
  735 
  736 /**
  737  * Set an internal fail_point structure from a human-readable failpoint string
  738  * in a lock-safe manner.
  739  */
  740 static int
  741 fail_point_set(struct fail_point *fp, char *buf)
  742 {
  743         struct fail_point_entry *ent, *ent_next;
  744         struct fail_point_setting *entries;
  745         bool should_wake_paused;
  746         bool should_truncate;
  747         int error;
  748 
  749         error = 0;
  750         should_wake_paused = false;
  751         should_truncate = false;
  752 
  753         /* Parse new entries. */
  754         /**
  755          * ref protects our new malloc'd stuff from being garbage collected
  756          * before we link it.
  757          */
  758         fail_point_setting_get_ref(fp);
  759         entries = fail_point_setting_new(fp);
  760         if (parse_fail_point(entries, buf) == NULL) {
  761                 STAILQ_REMOVE(&fp_setting_garbage, entries,
  762                         fail_point_setting, fs_garbage_link);
  763                 fail_point_setting_destroy(entries);
  764                 error = EINVAL;
  765                 goto end;
  766         }
  767 
  768         /**
  769          * Transfer the entries we are going to keep to a new list.
  770          * Get rid of useless zero probability entries, and entries with hit
  771          * count 0.
  772          * If 'off' is present, and it has no hit count set, then all entries
  773          *       after it are discarded since they are unreachable.
  774          */
  775         TAILQ_FOREACH_SAFE(ent, &entries->fp_entry_queue, fe_entries, ent_next) {
  776                 if (ent->fe_prob == 0 || ent->fe_count == 0) {
  777                         printf("Discarding entry which cannot execute %s\n",
  778                                 fail_type_strings[ent->fe_type].name);
  779                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
  780                                 fe_entries);
  781                         fp_free(ent);
  782                         continue;
  783                 } else if (should_truncate) {
  784                         printf("Discarding unreachable entry %s\n",
  785                                 fail_type_strings[ent->fe_type].name);
  786                         TAILQ_REMOVE(&entries->fp_entry_queue, ent,
  787                                 fe_entries);
  788                         fp_free(ent);
  789                         continue;
  790                 }
  791 
  792                 if (ent->fe_type == FAIL_POINT_OFF) {
  793                         should_wake_paused = true;
  794                         if (ent->fe_count == FE_COUNT_UNTRACKED) {
  795                                 should_truncate = true;
  796                                 TAILQ_REMOVE(&entries->fp_entry_queue, ent,
  797                                         fe_entries);
  798                                 fp_free(ent);
  799                         }
  800                 } else if (ent->fe_type == FAIL_POINT_PAUSE) {
  801                         should_truncate = true;
  802                 } else if (ent->fe_type == FAIL_POINT_SLEEP && (fp->fp_flags &
  803                         FAIL_POINT_NONSLEEPABLE)) {
  804                         /**
  805                          * If this fail point is annotated as being in a
  806                          * non-sleepable ctx, convert sleep to delay and
  807                          * convert the msec argument to usecs.
  808                          */
  809                         printf("Sleep call request on fail point in "
  810                                 "non-sleepable context; using delay instead "
  811                                 "of sleep\n");
  812                         ent->fe_type = FAIL_POINT_DELAY;
  813                         ent->fe_arg *= 1000;
  814                 }
  815         }
  816 
  817         if (TAILQ_EMPTY(&entries->fp_entry_queue)) {
  818                 entries = fail_point_swap_settings(fp, NULL);
  819                 if (entries != NULL)
  820                         wakeup(FP_PAUSE_CHANNEL(fp));
  821         } else {
  822                 if (should_wake_paused)
  823                         wakeup(FP_PAUSE_CHANNEL(fp));
  824                 fail_point_swap_settings(fp, entries);
  825         }
  826 
  827 end:
  828 #ifdef IWARNING
  829         if (error)
  830                 IWARNING("Failed to set %s %s to %s",
  831                     fp->fp_name, fp->fp_location, buf);
  832         else
  833                 INOTICE("Set %s %s to %s",
  834                     fp->fp_name, fp->fp_location, buf);
  835 #endif /* IWARNING */
  836 
  837         fail_point_setting_release_ref(fp);
  838         return (error);
  839 }
  840 
  841 #define MAX_FAIL_POINT_BUF      1023
  842 
  843 /**
  844  * Handle kernel failpoint set/get.
  845  */
  846 int
  847 fail_point_sysctl(SYSCTL_HANDLER_ARGS)
  848 {
  849         struct fail_point *fp;
  850         char *buf;
  851         struct sbuf sb, *sb_check;
  852         int error;
  853 
  854         buf = NULL;
  855         error = 0;
  856         fp = arg1;
  857 
  858         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
  859         if (sb_check != &sb)
  860                 return (ENOMEM);
  861 
  862         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
  863 
  864         /* Setting */
  865         /**
  866          * Lock protects any new entries from being garbage collected before we
  867          * can link them to the fail point.
  868          */
  869         sx_xlock(&sx_fp_set);
  870         if (req->newptr) {
  871                 if (req->newlen > MAX_FAIL_POINT_BUF) {
  872                         error = EINVAL;
  873                         goto out;
  874                 }
  875 
  876                 buf = fp_malloc(req->newlen + 1, M_WAITOK);
  877 
  878                 error = SYSCTL_IN(req, buf, req->newlen);
  879                 if (error)
  880                         goto out;
  881                 buf[req->newlen] = '\0';
  882 
  883                 error = fail_point_set(fp, buf);
  884         }
  885 
  886         fail_point_garbage_collect();
  887         sx_xunlock(&sx_fp_set);
  888 
  889         /* Retrieving. */
  890         fail_point_get(fp, &sb, false);
  891 
  892 out:
  893         sbuf_finish(&sb);
  894         sbuf_delete(&sb);
  895 
  896         if (buf)
  897                 fp_free(buf);
  898 
  899         return (error);
  900 }
  901 
  902 int
  903 fail_point_sysctl_status(SYSCTL_HANDLER_ARGS)
  904 {
  905         struct fail_point *fp;
  906         struct sbuf sb, *sb_check;
  907 
  908         fp = arg1;
  909 
  910         sb_check = sbuf_new(&sb, NULL, 1024, SBUF_AUTOEXTEND);
  911         if (sb_check != &sb)
  912                 return (ENOMEM);
  913 
  914         sbuf_set_drain(&sb, (sbuf_drain_func *)fail_sysctl_drain_func, req);
  915 
  916         /* Retrieving. */
  917         fail_point_get(fp, &sb, true);
  918 
  919         sbuf_finish(&sb);
  920         sbuf_delete(&sb);
  921 
  922         /**
  923          * Lock protects any new entries from being garbage collected before we
  924          * can link them to the fail point.
  925          */
  926         sx_xlock(&sx_fp_set);
  927         fail_point_garbage_collect();
  928         sx_xunlock(&sx_fp_set);
  929 
  930         return (0);
  931 }
  932 
  933 int
  934 fail_sysctl_drain_func(void *sysctl_args, const char *buf, int len)
  935 {
  936         struct sysctl_req *sa;
  937         int error;
  938 
  939         sa = sysctl_args;
  940 
  941         error = SYSCTL_OUT(sa, buf, len);
  942 
  943         if (error == ENOMEM)
  944                 return (-1);
  945         else
  946                 return (len);
  947 }
  948 
  949 /**
  950  * Internal helper function to translate a human-readable failpoint string
  951  * into a internally-parsable fail_point structure.
  952  */
  953 static char *
  954 parse_fail_point(struct fail_point_setting *ents, char *p)
  955 {
  956         /*  <fail_point> ::
  957          *      <term> ( "->" <term> )*
  958          */
  959         uint8_t term_count;
  960 
  961         term_count = 1;
  962 
  963         p = parse_term(ents, p);
  964         if (p == NULL)
  965                 return (NULL);
  966 
  967         while (*p != '\0') {
  968                 term_count++;
  969                 if (p[0] != '-' || p[1] != '>' ||
  970                         (p = parse_term(ents, p+2)) == NULL ||
  971                         term_count > FP_MAX_ENTRY_COUNT)
  972                         return (NULL);
  973         }
  974         return (p);
  975 }
  976 
  977 /**
  978  * Internal helper function to parse an individual term from a failpoint.
  979  */
  980 static char *
  981 parse_term(struct fail_point_setting *ents, char *p)
  982 {
  983         struct fail_point_entry *ent;
  984 
  985         ent = fail_point_entry_new(ents);
  986 
  987         /*
  988          * <term> ::
  989          *     ( (<float> "%") | (<integer> "*" ) )*
  990          *     <type>
  991          *     [ "(" <integer> ")" ]
  992          *     [ "[pid " <integer> "]" ]
  993          */
  994 
  995         /* ( (<float> "%") | (<integer> "*" ) )* */
  996         while (isdigit(*p) || *p == '.') {
  997                 int units, decimal;
  998 
  999                 p = parse_number(&units, &decimal, p);
 1000                 if (p == NULL)
 1001                         return (NULL);
 1002 
 1003                 if (*p == '%') {
 1004                         if (units > 100) /* prevent overflow early */
 1005                                 units = 100;
 1006                         ent->fe_prob = units * (PROB_MAX / 100) + decimal;
 1007                         if (ent->fe_prob > PROB_MAX)
 1008                                 ent->fe_prob = PROB_MAX;
 1009                 } else if (*p == '*') {
 1010                         if (!units || units < 0 || decimal)
 1011                                 return (NULL);
 1012                         ent->fe_count = units;
 1013                 } else
 1014                         return (NULL);
 1015                 p++;
 1016         }
 1017 
 1018         /* <type> */
 1019         p = parse_type(ent, p);
 1020         if (p == NULL)
 1021                 return (NULL);
 1022         if (*p == '\0')
 1023                 return (p);
 1024 
 1025         /* [ "(" <integer> ")" ] */
 1026         if (*p != '(')
 1027                 return (p);
 1028         p++;
 1029         if (!isdigit(*p) && *p != '-')
 1030                 return (NULL);
 1031         ent->fe_arg = strtol(p, &p, 0);
 1032         if (*p++ != ')')
 1033                 return (NULL);
 1034 
 1035         /* [ "[pid " <integer> "]" ] */
 1036 #define PID_STRING "[pid "
 1037         if (strncmp(p, PID_STRING, sizeof(PID_STRING) - 1) != 0)
 1038                 return (p);
 1039         p += sizeof(PID_STRING) - 1;
 1040         if (!isdigit(*p))
 1041                 return (NULL);
 1042         ent->fe_pid = strtol(p, &p, 0);
 1043         if (*p++ != ']')
 1044                 return (NULL);
 1045 
 1046         return (p);
 1047 }
 1048 
 1049 /**
 1050  * Internal helper function to parse a numeric for a failpoint term.
 1051  */
 1052 static char *
 1053 parse_number(int *out_units, int *out_decimal, char *p)
 1054 {
 1055         char *old_p;
 1056 
 1057         /**
 1058          *  <number> ::
 1059          *      <integer> [ "." <integer> ] |
 1060          *      "." <integer>
 1061          */
 1062 
 1063         /* whole part */
 1064         old_p = p;
 1065         *out_units = strtol(p, &p, 10);
 1066         if (p == old_p && *p != '.')
 1067                 return (NULL);
 1068 
 1069         /* fractional part */
 1070         *out_decimal = 0;
 1071         if (*p == '.') {
 1072                 int digits = 0;
 1073                 p++;
 1074                 while (isdigit(*p)) {
 1075                         int digit = *p - '';
 1076                         if (digits < PROB_DIGITS - 2)
 1077                                 *out_decimal = *out_decimal * 10 + digit;
 1078                         else if (digits == PROB_DIGITS - 2 && digit >= 5)
 1079                                 (*out_decimal)++;
 1080                         digits++;
 1081                         p++;
 1082                 }
 1083                 if (!digits) /* need at least one digit after '.' */
 1084                         return (NULL);
 1085                 while (digits++ < PROB_DIGITS - 2) /* add implicit zeros */
 1086                         *out_decimal *= 10;
 1087         }
 1088 
 1089         return (p); /* success */
 1090 }
 1091 
 1092 /**
 1093  * Internal helper function to parse an individual type for a failpoint term.
 1094  */
 1095 static char *
 1096 parse_type(struct fail_point_entry *ent, char *beg)
 1097 {
 1098         enum fail_point_t type;
 1099         int len;
 1100 
 1101         for (type = FAIL_POINT_OFF; type < FAIL_POINT_NUMTYPES; type++) {
 1102                 len = fail_type_strings[type].nmlen;
 1103                 if (strncmp(fail_type_strings[type].name, beg, len) == 0) {
 1104                         ent->fe_type = type;
 1105                         return (beg + len);
 1106                 }
 1107         }
 1108         return (NULL);
 1109 }
 1110 
 1111 /* The fail point sysctl tree. */
 1112 SYSCTL_NODE(_debug, OID_AUTO, fail_point, CTLFLAG_RW, 0, "fail points");
 1113 
 1114 /* Debugging/testing stuff for fail point */
 1115 static int
 1116 sysctl_test_fail_point(SYSCTL_HANDLER_ARGS)
 1117 {
 1118 
 1119         KFAIL_POINT_RETURN(DEBUG_FP, test_fail_point);
 1120         return (0);
 1121 }
 1122 SYSCTL_OID(_debug_fail_point, OID_AUTO, test_trigger_fail_point,
 1123         CTLTYPE_STRING | CTLFLAG_RD, NULL, 0, sysctl_test_fail_point, "A",
 1124         "Trigger test fail points");

Cache object: 245d3a27b086addaeb2b31527a52fef7


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