The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/kern/subr_unit.c

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    1 /*-
    2  * Copyright (c) 2004 Poul-Henning Kamp
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice, this list of conditions and the following disclaimer.
   10  * 2. Redistributions in binary form must reproduce the above copyright
   11  *    notice, this list of conditions and the following disclaimer in the
   12  *    documentation and/or other materials provided with the distribution.
   13  *
   14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   16  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   17  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   18  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   19  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   20  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   21  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   22  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   23  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   24  * SUCH DAMAGE.
   25  *
   26  * $FreeBSD: releng/6.4/sys/kern/subr_unit.c 143550 2005-03-14 06:51:29Z phk $
   27  *
   28  *
   29  * Unit number allocation functions.
   30  *
   31  * These functions implement a mixed run-length/bitmap management of unit
   32  * number spaces in a very memory efficient manner.
   33  *
   34  * Allocation policy is always lowest free number first.
   35  *
   36  * A return value of -1 signals that no more unit numbers are available.
   37  *
   38  * There is no cost associated with the range of unitnumbers, so unless
   39  * the resource really is finite, specify INT_MAX to new_unrhdr() and
   40  * forget about checking the return value.
   41  *
   42  * If a mutex is not provided when the unit number space is created, a
   43  * default global mutex is used.  The advantage to passing a mutex in, is
   44  * that the the alloc_unrl() function can be called with the mutex already
   45  * held (it will not be released by alloc_unrl()).
   46  *
   47  * The allocation function alloc_unr{l}() never sleeps (but it may block on
   48  * the mutex of course).
   49  *
   50  * Freeing a unit number may require allocating memory, and can therefore
   51  * sleep so the free_unr() function does not come in a pre-locked variant.
   52  *
   53  * A userland test program is included.
   54  *
   55  * Memory usage is a very complex function of the the exact allocation
   56  * pattern, but always very compact:
   57  *    * For the very typical case where a single unbroken run of unit
   58  *      numbers are allocated 44 bytes are used on i386.
   59  *    * For a unit number space of 1000 units and the random pattern
   60  *      in the usermode test program included, the worst case usage
   61  *      was 252 bytes on i386 for 500 allocated and 500 free units.
   62  *    * For a unit number space of 10000 units and the random pattern
   63  *      in the usermode test program included, the worst case usage
   64  *      was 798 bytes on i386 for 5000 allocated and 5000 free units.
   65  *    * The worst case is where every other unit number is allocated and
   66  *      the the rest are free.  In that case 44 + N/4 bytes are used where
   67  *      N is the number of the highest unit allocated.
   68  */
   69 
   70 #include <sys/types.h>
   71 #include <sys/queue.h>
   72 #include <sys/bitstring.h>
   73 
   74 #ifdef _KERNEL
   75 
   76 #include <sys/param.h>
   77 #include <sys/malloc.h>
   78 #include <sys/kernel.h>
   79 #include <sys/systm.h>
   80 #include <sys/limits.h>
   81 #include <sys/lock.h>
   82 #include <sys/mutex.h>
   83 
   84 /*
   85  * In theory it would be smarter to allocate the individual blocks
   86  * with the zone allocator, but at this time the expectation is that
   87  * there will typically not even be enough allocations to fill a single
   88  * page, so we stick with malloc for now.
   89  */
   90 static MALLOC_DEFINE(M_UNIT, "Unitno", "Unit number allocation");
   91 
   92 #define Malloc(foo) malloc(foo, M_UNIT, M_WAITOK | M_ZERO)
   93 #define Free(foo) free(foo, M_UNIT)
   94 
   95 static struct mtx unitmtx;
   96 
   97 MTX_SYSINIT(unit, &unitmtx, "unit# allocation", MTX_DEF);
   98 
   99 #else /* ...USERLAND */
  100 
  101 #include <stdio.h>
  102 #include <stdlib.h>
  103 #include <string.h>
  104 
  105 #define KASSERT(cond, arg) \
  106         do { \
  107                 if (!(cond)) { \
  108                         printf arg; \
  109                         abort(); \
  110                 } \
  111         } while (0)
  112 
  113 static int no_alloc;
  114 #define Malloc(foo) _Malloc(foo, __LINE__)
  115 static void *
  116 _Malloc(size_t foo, int line)
  117 {
  118 
  119         KASSERT(no_alloc == 0, ("malloc in wrong place() line %d", line));
  120         return (calloc(foo, 1));
  121 }
  122 #define Free(foo) free(foo)
  123 
  124 struct unrhdr;
  125 
  126 
  127 struct mtx {
  128         int     state;
  129 } unitmtx;
  130 
  131 static void
  132 mtx_lock(struct mtx *mp)
  133 {
  134         KASSERT(mp->state == 0, ("mutex already locked"));
  135         mp->state = 1;
  136 }
  137 
  138 static void
  139 mtx_unlock(struct mtx *mp)
  140 {
  141         KASSERT(mp->state == 1, ("mutex not locked"));
  142         mp->state = 0;
  143 }
  144 
  145 #define MA_OWNED        9
  146 
  147 static void
  148 mtx_assert(struct mtx *mp, int flag)
  149 {
  150         if (flag == MA_OWNED) {
  151                 KASSERT(mp->state == 1, ("mtx_assert(MA_OWNED) not true"));
  152         }
  153 }
  154 
  155 #define CTASSERT(foo)
  156 
  157 #endif /* USERLAND */
  158 
  159 /*
  160  * This is our basic building block.
  161  *
  162  * It can be used in three different ways depending on the value of the ptr
  163  * element:
  164  *     If ptr is NULL, it represents a run of free items.
  165  *     If ptr points to the unrhdr it represents a run of allocated items.
  166  *     Otherwise it points to an bitstring of allocated items.
  167  *
  168  * For runs the len field is the length of the run.
  169  * For bitmaps the len field represents the number of allocated items.
  170  *
  171  * The bitmap is the same size as struct unr to optimize memory management.
  172  */
  173 struct unr {
  174         TAILQ_ENTRY(unr)        list;
  175         u_int                   len;
  176         void                    *ptr;
  177 };
  178 
  179 struct unrb {
  180         u_char                  busy;
  181         bitstr_t                map[sizeof(struct unr) - 1];
  182 };
  183 
  184 CTASSERT(sizeof(struct unr) == sizeof(struct unrb));
  185 
  186 /* Number of bits in the bitmap */
  187 #define NBITS   ((int)sizeof(((struct unrb *)NULL)->map) * 8)
  188 
  189 /* Header element for a unr number space. */
  190 
  191 struct unrhdr {
  192         TAILQ_HEAD(unrhd,unr)   head;
  193         u_int                   low;    /* Lowest item */
  194         u_int                   high;   /* Highest item */
  195         u_int                   busy;   /* Count of allocated items */
  196         u_int                   alloc;  /* Count of memory allocations */
  197         u_int                   first;  /* items in allocated from start */
  198         u_int                   last;   /* items free at end */
  199         struct mtx              *mtx;
  200 };
  201 
  202 
  203 #if defined(DIAGNOSTIC) || !defined(_KERNEL)
  204 /*
  205  * Consistency check function.
  206  *
  207  * Checks the internal consistency as well as we can.
  208  * 
  209  * Called at all boundaries of this API.
  210  */
  211 static void
  212 check_unrhdr(struct unrhdr *uh, int line)
  213 {
  214         struct unr *up;
  215         struct unrb *ub;
  216         u_int x, y, z, w;
  217 
  218         y = uh->first;
  219         z = 0;
  220         TAILQ_FOREACH(up, &uh->head, list) {
  221                 z++;
  222                 if (up->ptr != uh && up->ptr != NULL) {
  223                         ub = up->ptr;
  224                         KASSERT (up->len <= NBITS,
  225                             ("UNR inconsistency: len %u max %d (line %d)\n",
  226                             up->len, NBITS, line));
  227                         z++;
  228                         w = 0;
  229                         for (x = 0; x < up->len; x++)
  230                                 if (bit_test(ub->map, x))
  231                                         w++;
  232                         KASSERT (w == ub->busy,
  233                             ("UNR inconsistency: busy %u found %u (line %d)\n",
  234                             ub->busy, w, line));
  235                         y += w;
  236                 } else if (up->ptr != NULL) 
  237                         y += up->len;
  238         }
  239         KASSERT (y == uh->busy,
  240             ("UNR inconsistency: items %u found %u (line %d)\n",
  241             uh->busy, y, line));
  242         KASSERT (z == uh->alloc,
  243             ("UNR inconsistency: chunks %u found %u (line %d)\n",
  244             uh->alloc, z, line));
  245 }
  246 
  247 #else
  248 
  249 static __inline void
  250 check_unrhdr(struct unrhdr *uh, int line)
  251 {
  252 
  253 }
  254 
  255 #endif
  256 
  257 
  258 /*
  259  * Userland memory management.  Just use calloc and keep track of how
  260  * many elements we have allocated for check_unrhdr().
  261  */
  262 
  263 static __inline void *
  264 new_unr(struct unrhdr *uh, void **p1, void **p2)
  265 {
  266         void *p;
  267 
  268         uh->alloc++;
  269         KASSERT(*p1 != NULL || *p2 != NULL, ("Out of cached memory"));
  270         if (*p1 != NULL) {
  271                 p = *p1;
  272                 *p1 = NULL;
  273                 return (p);
  274         } else {
  275                 p = *p2;
  276                 *p2 = NULL;
  277                 return (p);
  278         }
  279 }
  280 
  281 static __inline void
  282 delete_unr(struct unrhdr *uh, void *ptr)
  283 {
  284 
  285         uh->alloc--;
  286         Free(ptr);
  287 }
  288 
  289 /*
  290  * Allocate a new unrheader set.
  291  *
  292  * Highest and lowest valid values given as paramters.
  293  */
  294 
  295 struct unrhdr *
  296 new_unrhdr(int low, int high, struct mtx *mutex)
  297 {
  298         struct unrhdr *uh;
  299 
  300         KASSERT(low <= high,
  301             ("UNR: use error: new_unrhdr(%u, %u)", low, high));
  302         uh = Malloc(sizeof *uh);
  303         if (mutex != NULL)
  304                 uh->mtx = mutex;
  305         else
  306                 uh->mtx = &unitmtx;
  307         TAILQ_INIT(&uh->head);
  308         uh->low = low;
  309         uh->high = high;
  310         uh->first = 0;
  311         uh->last = 1 + (high - low);
  312         check_unrhdr(uh, __LINE__);
  313         return (uh);
  314 }
  315 
  316 void
  317 delete_unrhdr(struct unrhdr *uh)
  318 {
  319 
  320         check_unrhdr(uh, __LINE__);
  321         KASSERT(uh->busy == 0, ("unrhdr has %u allocations", uh->busy));
  322         KASSERT(uh->alloc == 0, ("UNR memory leak in delete_unrhdr"));
  323         Free(uh);
  324 }
  325 
  326 static __inline int
  327 is_bitmap(struct unrhdr *uh, struct unr *up)
  328 {
  329         return (up->ptr != uh && up->ptr != NULL);
  330 }
  331 
  332 /*
  333  * Look for sequence of items which can be combined into a bitmap, if
  334  * multiple are present, take the one which saves most memory.
  335  * 
  336  * Return (1) if a sequence was found to indicate that another call
  337  * might be able to do more.  Return (0) if we found no suitable sequence.
  338  *
  339  * NB: called from alloc_unr(), no new memory allocation allowed.
  340  */
  341 static int
  342 optimize_unr(struct unrhdr *uh)
  343 {
  344         struct unr *up, *uf, *us;
  345         struct unrb *ub, *ubf;
  346         u_int a, l, ba;
  347 
  348         /*
  349          * Look for the run of items (if any) which when collapsed into
  350          * a bitmap would save most memory.
  351          */
  352         us = NULL;
  353         ba = 0;
  354         TAILQ_FOREACH(uf, &uh->head, list) {
  355                 if (uf->len >= NBITS)
  356                         continue;
  357                 a = 1;
  358                 if (is_bitmap(uh, uf))
  359                         a++;
  360                 l = uf->len;
  361                 up = uf;
  362                 while (1) {
  363                         up = TAILQ_NEXT(up, list);
  364                         if (up == NULL)
  365                                 break;
  366                         if ((up->len + l) > NBITS)
  367                                 break;
  368                         a++;
  369                         if (is_bitmap(uh, up))
  370                                 a++;
  371                         l += up->len;
  372                 }
  373                 if (a > ba) {
  374                         ba = a;
  375                         us = uf;
  376                 }
  377         }
  378         if (ba < 3)
  379                 return (0);
  380 
  381         /*
  382          * If the first element is not a bitmap, make it one.
  383          * Trying to do so without allocating more memory complicates things
  384          * a bit
  385          */
  386         if (!is_bitmap(uh, us)) {
  387                 uf = TAILQ_NEXT(us, list);
  388                 TAILQ_REMOVE(&uh->head, us, list);
  389                 a = us->len;
  390                 l = us->ptr == uh ? 1 : 0;
  391                 ub = (void *)us;
  392                 ub->busy = 0;
  393                 if (l) {
  394                         bit_nset(ub->map, 0, a);
  395                         ub->busy += a;
  396                 } else {
  397                         bit_nclear(ub->map, 0, a);
  398                 }
  399                 if (!is_bitmap(uh, uf)) {
  400                         if (uf->ptr == NULL) {
  401                                 bit_nclear(ub->map, a, a + uf->len - 1);
  402                         } else {
  403                                 bit_nset(ub->map, a, a + uf->len - 1);
  404                                 ub->busy += uf->len;
  405                         }
  406                         uf->ptr = ub;
  407                         uf->len += a;
  408                         us = uf;
  409                 } else {
  410                         ubf = uf->ptr;
  411                         for (l = 0; l < uf->len; l++, a++) {
  412                                 if (bit_test(ubf->map, l)) {
  413                                         bit_set(ub->map, a);
  414                                         ub->busy++;
  415                                 } else {
  416                                         bit_clear(ub->map, a);
  417                                 }
  418                         }
  419                         uf->len = a;
  420                         delete_unr(uh, uf->ptr);
  421                         uf->ptr = ub;
  422                         us = uf;
  423                 }
  424         }
  425         ub = us->ptr;
  426         while (1) {
  427                 uf = TAILQ_NEXT(us, list);
  428                 if (uf == NULL)
  429                         return (1);
  430                 if (uf->len + us->len > NBITS)
  431                         return (1);
  432                 if (uf->ptr == NULL) {
  433                         bit_nclear(ub->map, us->len, us->len + uf->len - 1);
  434                         us->len += uf->len;
  435                         TAILQ_REMOVE(&uh->head, uf, list);
  436                         delete_unr(uh, uf);
  437                 } else if (uf->ptr == uh) {
  438                         bit_nset(ub->map, us->len, us->len + uf->len - 1);
  439                         ub->busy += uf->len;
  440                         us->len += uf->len;
  441                         TAILQ_REMOVE(&uh->head, uf, list);
  442                         delete_unr(uh, uf);
  443                 } else {
  444                         ubf = uf->ptr;
  445                         for (l = 0; l < uf->len; l++, us->len++) {
  446                                 if (bit_test(ubf->map, l)) {
  447                                         bit_set(ub->map, us->len);
  448                                         ub->busy++;
  449                                 } else {
  450                                         bit_clear(ub->map, us->len);
  451                                 }
  452                         }
  453                         TAILQ_REMOVE(&uh->head, uf, list);
  454                         delete_unr(uh, ubf);
  455                         delete_unr(uh, uf);
  456                 }
  457         }
  458 }
  459 
  460 /*
  461  * See if a given unr should be collapsed with a neighbor.
  462  *
  463  * NB: called from alloc_unr(), no new memory allocation allowed.
  464  */
  465 static void
  466 collapse_unr(struct unrhdr *uh, struct unr *up)
  467 {
  468         struct unr *upp;
  469         struct unrb *ub;
  470 
  471         /* If bitmap is all set or clear, change it to runlength */
  472         if (is_bitmap(uh, up)) {
  473                 ub = up->ptr;
  474                 if (ub->busy == up->len) {
  475                         delete_unr(uh, up->ptr);
  476                         up->ptr = uh;
  477                 } else if (ub->busy == 0) {
  478                         delete_unr(uh, up->ptr);
  479                         up->ptr = NULL;
  480                 }
  481         }
  482 
  483         /* If nothing left in runlength, delete it */
  484         if (up->len == 0) {
  485                 upp = TAILQ_PREV(up, unrhd, list);
  486                 if (upp == NULL)
  487                         upp = TAILQ_NEXT(up, list);
  488                 TAILQ_REMOVE(&uh->head, up, list);
  489                 delete_unr(uh, up);
  490                 up = upp;
  491         }
  492 
  493         /* If we have "hot-spot" still, merge with neighbor if possible */
  494         if (up != NULL) {
  495                 upp = TAILQ_PREV(up, unrhd, list);
  496                 if (upp != NULL && up->ptr == upp->ptr) {
  497                         up->len += upp->len;
  498                         TAILQ_REMOVE(&uh->head, upp, list);
  499                         delete_unr(uh, upp);
  500                         }
  501                 upp = TAILQ_NEXT(up, list);
  502                 if (upp != NULL && up->ptr == upp->ptr) {
  503                         up->len += upp->len;
  504                         TAILQ_REMOVE(&uh->head, upp, list);
  505                         delete_unr(uh, upp);
  506                 }
  507         }
  508 
  509         /* Merge into ->first if possible */
  510         upp = TAILQ_FIRST(&uh->head);
  511         if (upp != NULL && upp->ptr == uh) {
  512                 uh->first += upp->len;
  513                 TAILQ_REMOVE(&uh->head, upp, list);
  514                 delete_unr(uh, upp);
  515                 if (up == upp)
  516                         up = NULL;
  517         }
  518 
  519         /* Merge into ->last if possible */
  520         upp = TAILQ_LAST(&uh->head, unrhd);
  521         if (upp != NULL && upp->ptr == NULL) {
  522                 uh->last += upp->len;
  523                 TAILQ_REMOVE(&uh->head, upp, list);
  524                 delete_unr(uh, upp);
  525                 if (up == upp)
  526                         up = NULL;
  527         }
  528 
  529         /* Try to make bitmaps */
  530         while (optimize_unr(uh))
  531                 continue;
  532 }
  533 
  534 /*
  535  * Allocate a free unr.
  536  */
  537 int
  538 alloc_unrl(struct unrhdr *uh)
  539 {
  540         struct unr *up;
  541         struct unrb *ub;
  542         u_int x;
  543         int y;
  544 
  545         mtx_assert(uh->mtx, MA_OWNED);
  546         check_unrhdr(uh, __LINE__);
  547         x = uh->low + uh->first;
  548 
  549         up = TAILQ_FIRST(&uh->head);
  550 
  551         /*
  552          * If we have an ideal split, just adjust the first+last
  553          */
  554         if (up == NULL && uh->last > 0) {
  555                 uh->first++;
  556                 uh->last--;
  557                 uh->busy++;
  558                 return (x);
  559         }
  560 
  561         /*
  562          * We can always allocate from the first list element, so if we have 
  563          * nothing on the list, we must have run out of unit numbers.
  564          */
  565         if (up == NULL)
  566                 return (-1);
  567 
  568         KASSERT(up->ptr != uh, ("UNR first element is allocated"));
  569 
  570         if (up->ptr == NULL) {  /* free run */
  571                 uh->first++;
  572                 up->len--;
  573         } else {                /* bitmap */
  574                 ub = up->ptr;
  575                 KASSERT(ub->busy < up->len, ("UNR bitmap confusion"));
  576                 bit_ffc(ub->map, up->len, &y);
  577                 KASSERT(y != -1, ("UNR corruption: No clear bit in bitmap."));
  578                 bit_set(ub->map, y);
  579                 ub->busy++;
  580                 x += y;
  581         }
  582         uh->busy++;
  583         collapse_unr(uh, up);
  584         return (x);
  585 }
  586 
  587 int
  588 alloc_unr(struct unrhdr *uh)
  589 {
  590         int i;
  591 
  592         mtx_lock(uh->mtx);
  593         i = alloc_unrl(uh);
  594         mtx_unlock(uh->mtx);
  595         return (i);
  596 }
  597 
  598 /*
  599  * Free a unr.
  600  *
  601  * If we can save unrs by using a bitmap, do so.
  602  */
  603 static void
  604 free_unrl(struct unrhdr *uh, u_int item, void **p1, void **p2)
  605 {
  606         struct unr *up, *upp, *upn;
  607         struct unrb *ub;
  608         u_int pl;
  609 
  610         KASSERT(item >= uh->low && item <= uh->high,
  611             ("UNR: free_unr(%u) out of range [%u...%u]",
  612              item, uh->low, uh->high));
  613         check_unrhdr(uh, __LINE__);
  614         item -= uh->low;
  615         upp = TAILQ_FIRST(&uh->head);
  616         /*
  617          * Freeing in the ideal split case
  618          */
  619         if (item + 1 == uh->first && upp == NULL) {
  620                 uh->last++;
  621                 uh->first--;
  622                 uh->busy--;
  623                 check_unrhdr(uh, __LINE__);
  624                 return;
  625         }
  626         /*
  627          * Freeing in the ->first section.  Create a run starting at the
  628          * freed item.  The code below will subdivide it.
  629          */
  630         if (item < uh->first) {
  631                 up = new_unr(uh, p1, p2);
  632                 up->ptr = uh;
  633                 up->len = uh->first - item;
  634                 TAILQ_INSERT_HEAD(&uh->head, up, list);
  635                 uh->first -= up->len;
  636         }
  637 
  638         item -= uh->first;
  639 
  640         /* Find the item which contains the unit we want to free */
  641         TAILQ_FOREACH(up, &uh->head, list) {
  642                 if (up->len > item)
  643                         break;
  644                 item -= up->len;
  645         }
  646 
  647         /* Handle bitmap items */
  648         if (is_bitmap(uh, up)) {
  649                 ub = up->ptr;
  650                 
  651                 KASSERT(bit_test(ub->map, item) != 0,
  652                     ("UNR: Freeing free item %d (bitmap)\n", item));
  653                 bit_clear(ub->map, item);
  654                 uh->busy--;
  655                 ub->busy--;
  656                 collapse_unr(uh, up);
  657                 return;
  658         }
  659 
  660         KASSERT(up->ptr == uh, ("UNR Freeing free item %d (run))\n", item));
  661 
  662         /* Just this one left, reap it */
  663         if (up->len == 1) {
  664                 up->ptr = NULL;
  665                 uh->busy--;
  666                 collapse_unr(uh, up);
  667                 return;
  668         }
  669 
  670         /* Check if we can shift the item into the previous 'free' run */
  671         upp = TAILQ_PREV(up, unrhd, list);
  672         if (item == 0 && upp != NULL && upp->ptr == NULL) {
  673                 upp->len++;
  674                 up->len--;
  675                 uh->busy--;
  676                 collapse_unr(uh, up);
  677                 return;
  678         }
  679 
  680         /* Check if we can shift the item to the next 'free' run */
  681         upn = TAILQ_NEXT(up, list);
  682         if (item == up->len - 1 && upn != NULL && upn->ptr == NULL) {
  683                 upn->len++;
  684                 up->len--;
  685                 uh->busy--;
  686                 collapse_unr(uh, up);
  687                 return;
  688         }
  689 
  690         /* Split off the tail end, if any. */
  691         pl = up->len - (1 + item);
  692         if (pl > 0) {
  693                 upp = new_unr(uh, p1, p2);
  694                 upp->ptr = uh;
  695                 upp->len = pl;
  696                 TAILQ_INSERT_AFTER(&uh->head, up, upp, list);
  697         }
  698 
  699         /* Split off head end, if any */
  700         if (item > 0) {
  701                 upp = new_unr(uh, p1, p2);
  702                 upp->len = item;
  703                 upp->ptr = uh;
  704                 TAILQ_INSERT_BEFORE(up, upp, list);
  705         }
  706         up->len = 1;
  707         up->ptr = NULL;
  708         uh->busy--;
  709         collapse_unr(uh, up);
  710 }
  711 
  712 void
  713 free_unr(struct unrhdr *uh, u_int item)
  714 {
  715         void *p1, *p2;
  716 
  717         p1 = Malloc(sizeof(struct unr));
  718         p2 = Malloc(sizeof(struct unr));
  719         mtx_lock(uh->mtx);
  720         free_unrl(uh, item, &p1, &p2);
  721         mtx_unlock(uh->mtx);
  722         if (p1 != NULL)
  723                 Free(p1);
  724         if (p2 != NULL)
  725                 Free(p2);
  726 }
  727 
  728 #ifndef _KERNEL /* USERLAND test driver */
  729 
  730 /*
  731  * Simple stochastic test driver for the above functions
  732  */
  733 
  734 static void
  735 print_unr(struct unrhdr *uh, struct unr *up)
  736 {
  737         u_int x;
  738         struct unrb *ub;
  739 
  740         printf("  %p len = %5u ", up, up->len);
  741         if (up->ptr == NULL)
  742                 printf("free\n");
  743         else if (up->ptr == uh)
  744                 printf("alloc\n");
  745         else {
  746                 ub = up->ptr;
  747                 printf("bitmap(%d) [", ub->busy);
  748                 for (x = 0; x < up->len; x++) {
  749                         if (bit_test(ub->map, x))
  750                                 printf("#");
  751                         else 
  752                                 printf(" ");
  753                 }
  754                 printf("]\n");
  755         }
  756 }
  757 
  758 static void
  759 print_unrhdr(struct unrhdr *uh)
  760 {
  761         struct unr *up;
  762         u_int x;
  763 
  764         printf(
  765             "%p low = %u high = %u first = %u last = %u busy %u chunks = %u\n",
  766             uh, uh->low, uh->high, uh->first, uh->last, uh->busy, uh->alloc);
  767         x = uh->low + uh->first;
  768         TAILQ_FOREACH(up, &uh->head, list) {
  769                 printf("  from = %5u", x);
  770                 print_unr(uh, up);
  771                 if (up->ptr == NULL || up->ptr == uh)
  772                         x += up->len;
  773                 else
  774                         x += NBITS;
  775         }
  776 }
  777 
  778 /* Number of unrs to test */
  779 #define NN      10000
  780 
  781 int
  782 main(int argc __unused, const char **argv __unused)
  783 {
  784         struct unrhdr *uh;
  785         u_int i, x, m, j;
  786         char a[NN];
  787 
  788         setbuf(stdout, NULL);
  789         uh = new_unrhdr(0, NN - 1, NULL);
  790         print_unrhdr(uh);
  791 
  792         memset(a, 0, sizeof a);
  793 
  794         fprintf(stderr, "sizeof(struct unr) %d\n", sizeof (struct unr));
  795         fprintf(stderr, "sizeof(struct unrb) %d\n", sizeof (struct unrb));
  796         fprintf(stderr, "sizeof(struct unrhdr) %d\n", sizeof (struct unrhdr));
  797         fprintf(stderr, "NBITS %d\n", NBITS);
  798         x = 1;
  799         for (m = 0; m < NN * 100; m++) {
  800                 j = random();
  801                 i = (j >> 1) % NN;
  802 #if 0
  803                 if (a[i] && (j & 1))
  804                         continue;
  805 #endif
  806                 if (a[i]) {
  807                         printf("F %u\n", i);
  808                         free_unr(uh, i);
  809                         a[i] = 0;
  810                 } else {
  811                         no_alloc = 1;
  812                         i = alloc_unr(uh);
  813                         if (i != -1) {
  814                                 a[i] = 1;
  815                                 printf("A %u\n", i);
  816                         }
  817                         no_alloc = 0;
  818                 }
  819                 if (1)  /* XXX: change this for detailed debug printout */
  820                         print_unrhdr(uh);
  821                 check_unrhdr(uh, __LINE__);
  822         }
  823         for (i = 0; i < NN; i++) {
  824                 if (a[i]) {
  825                         printf("C %u\n", i);
  826                         free_unr(uh, i);
  827                         print_unrhdr(uh);
  828                 }
  829         }
  830         print_unrhdr(uh);
  831         delete_unrhdr(uh);
  832         return (0);
  833 }
  834 #endif

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