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

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    1 /*-
    2  * Copyright (c) 2002 Poul-Henning Kamp
    3  * Copyright (c) 2002 Networks Associates Technology, Inc.
    4  * All rights reserved.
    5  *
    6  * This software was developed for the FreeBSD Project by Poul-Henning Kamp
    7  * and NAI Labs, the Security Research Division of Network Associates, Inc.
    8  * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
    9  * DARPA CHATS research program.
   10  *
   11  * Redistribution and use in source and binary forms, with or without
   12  * modification, are permitted provided that the following conditions
   13  * are met:
   14  * 1. Redistributions of source code must retain the above copyright
   15  *    notice, this list of conditions and the following disclaimer.
   16  * 2. Redistributions in binary form must reproduce the above copyright
   17  *    notice, this list of conditions and the following disclaimer in the
   18  *    documentation and/or other materials provided with the distribution.
   19  * 3. The names of the authors may not be used to endorse or promote
   20  *    products derived from this software without specific prior written
   21  *    permission.
   22  *
   23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   33  * SUCH DAMAGE.
   34  */
   35 
   36 /*
   37  * XXX: How do we in general know that objects referenced in events
   38  * have not been destroyed before we get around to handle the event ?
   39  */
   40 
   41 #include <sys/cdefs.h>
   42 __FBSDID("$FreeBSD: releng/8.3/sys/geom/geom_event.c 227227 2011-11-06 16:58:17Z mav $");
   43 
   44 #include <sys/param.h>
   45 #include <sys/malloc.h>
   46 #include <sys/systm.h>
   47 #include <sys/kernel.h>
   48 #include <sys/lock.h>
   49 #include <sys/mutex.h>
   50 #include <sys/proc.h>
   51 #include <sys/errno.h>
   52 #include <sys/time.h>
   53 #include <geom/geom.h>
   54 #include <geom/geom_int.h>
   55 
   56 #include <machine/stdarg.h>
   57 
   58 TAILQ_HEAD(event_tailq_head, g_event);
   59 
   60 static struct event_tailq_head g_events = TAILQ_HEAD_INITIALIZER(g_events);
   61 static u_int g_pending_events;
   62 static TAILQ_HEAD(,g_provider) g_doorstep = TAILQ_HEAD_INITIALIZER(g_doorstep);
   63 static struct mtx g_eventlock;
   64 static int g_wither_work;
   65 
   66 #define G_N_EVENTREFS           20
   67 
   68 struct g_event {
   69         TAILQ_ENTRY(g_event)    events;
   70         g_event_t               *func;
   71         void                    *arg;
   72         int                     flag;
   73         void                    *ref[G_N_EVENTREFS];
   74 };
   75 
   76 #define EV_DONE         0x80000
   77 #define EV_WAKEUP       0x40000
   78 #define EV_CANCELED     0x20000
   79 #define EV_INPROGRESS   0x10000
   80 
   81 void
   82 g_waitidle(void)
   83 {
   84 
   85         g_topology_assert_not();
   86         mtx_assert(&Giant, MA_NOTOWNED);
   87 
   88         mtx_lock(&g_eventlock);
   89         while (!TAILQ_EMPTY(&g_events))
   90                 msleep(&g_pending_events, &g_eventlock, PPAUSE,
   91                     "g_waitidle", hz/5);
   92         mtx_unlock(&g_eventlock);
   93         curthread->td_pflags &= ~TDP_GEOM;
   94 }
   95 
   96 #if 0
   97 void
   98 g_waitidlelock(void)
   99 {
  100 
  101         g_topology_assert();
  102         mtx_lock(&g_eventlock);
  103         while (!TAILQ_EMPTY(&g_events)) {
  104                 g_topology_unlock();
  105                 msleep(&g_pending_events, &g_eventlock, PPAUSE,
  106                     "g_waitidlel", hz/5);
  107                 g_topology_lock();
  108         }
  109         mtx_unlock(&g_eventlock);
  110 }
  111 #endif
  112 
  113 void
  114 g_orphan_provider(struct g_provider *pp, int error)
  115 {
  116 
  117         /* G_VALID_PROVIDER(pp)  We likely lack topology lock */
  118         g_trace(G_T_TOPOLOGY, "g_orphan_provider(%p(%s), %d)",
  119             pp, pp->name, error);
  120         KASSERT(error != 0,
  121             ("g_orphan_provider(%p(%s), 0) error must be non-zero\n",
  122              pp, pp->name));
  123         
  124         pp->error = error;
  125         mtx_lock(&g_eventlock);
  126         KASSERT(!(pp->flags & G_PF_ORPHAN),
  127             ("g_orphan_provider(%p(%s)), already an orphan", pp, pp->name));
  128         pp->flags |= G_PF_ORPHAN;
  129         TAILQ_INSERT_TAIL(&g_doorstep, pp, orphan);
  130         mtx_unlock(&g_eventlock);
  131         wakeup(&g_wait_event);
  132 }
  133 
  134 /*
  135  * This function is called once on each provider which the event handler
  136  * finds on its g_doorstep.
  137  */
  138 
  139 static void
  140 g_orphan_register(struct g_provider *pp)
  141 {
  142         struct g_consumer *cp, *cp2;
  143         int wf;
  144 
  145         g_topology_assert();
  146         G_VALID_PROVIDER(pp);
  147         g_trace(G_T_TOPOLOGY, "g_orphan_register(%s)", pp->name);
  148 
  149         g_cancel_event(pp);
  150 
  151         wf = pp->flags & G_PF_WITHER;
  152         pp->flags &= ~G_PF_WITHER;
  153 
  154         /*
  155          * Tell all consumers the bad news.
  156          * Don't be surprised if they self-destruct.
  157          */
  158         cp = LIST_FIRST(&pp->consumers);
  159         while (cp != NULL) {
  160                 cp2 = LIST_NEXT(cp, consumers);
  161                 KASSERT(cp->geom->orphan != NULL,
  162                     ("geom %s has no orphan, class %s",
  163                     cp->geom->name, cp->geom->class->name));
  164                 cp->geom->orphan(cp);
  165                 cp = cp2;
  166         }
  167         if (LIST_EMPTY(&pp->consumers) && wf)
  168                 g_destroy_provider(pp);
  169         else
  170                 pp->flags |= wf;
  171 #ifdef notyet
  172         cp = LIST_FIRST(&pp->consumers);
  173         if (cp != NULL)
  174                 return;
  175         if (pp->geom->flags & G_GEOM_WITHER)
  176                 g_destroy_provider(pp);
  177 #endif
  178 }
  179 
  180 static int
  181 one_event(void)
  182 {
  183         struct g_event *ep;
  184         struct g_provider *pp;
  185 
  186         g_topology_assert();
  187         mtx_lock(&g_eventlock);
  188         TAILQ_FOREACH(pp, &g_doorstep, orphan) {
  189                 if (pp->nstart == pp->nend)
  190                         break;
  191         }
  192         if (pp != NULL) {
  193                 G_VALID_PROVIDER(pp);
  194                 TAILQ_REMOVE(&g_doorstep, pp, orphan);
  195                 mtx_unlock(&g_eventlock);
  196                 g_orphan_register(pp);
  197                 return (1);
  198         }
  199 
  200         ep = TAILQ_FIRST(&g_events);
  201         if (ep == NULL) {
  202                 wakeup(&g_pending_events);
  203                 return (0);
  204         }
  205         if (ep->flag & EV_INPROGRESS) {
  206                 mtx_unlock(&g_eventlock);
  207                 return (1);
  208         }
  209         ep->flag |= EV_INPROGRESS;
  210         mtx_unlock(&g_eventlock);
  211         g_topology_assert();
  212         ep->func(ep->arg, 0);
  213         g_topology_assert();
  214         mtx_lock(&g_eventlock);
  215         TAILQ_REMOVE(&g_events, ep, events);
  216         ep->flag &= ~EV_INPROGRESS;
  217         if (ep->flag & EV_WAKEUP) {
  218                 ep->flag |= EV_DONE;
  219                 mtx_unlock(&g_eventlock);
  220                 wakeup(ep);
  221         } else {
  222                 mtx_unlock(&g_eventlock);
  223                 g_free(ep);
  224         }
  225         return (1);
  226 }
  227 
  228 void
  229 g_run_events()
  230 {
  231         int i;
  232 
  233         for (;;) {
  234                 g_topology_lock();
  235                 while (one_event())
  236                         ;
  237                 mtx_assert(&g_eventlock, MA_OWNED);
  238                 i = g_wither_work;
  239                 if (i) {
  240                         mtx_unlock(&g_eventlock);
  241                         while (i) {
  242                                 i = g_wither_washer();
  243                                 g_wither_work = i & 1;
  244                                 i &= 2;
  245                         }
  246                         g_topology_unlock();
  247                 } else {
  248                         g_topology_unlock();
  249                         msleep(&g_wait_event, &g_eventlock, PRIBIO | PDROP,
  250                             "-", TAILQ_EMPTY(&g_doorstep) ? 0 : hz / 10);
  251                 }
  252         }
  253         /* NOTREACHED */
  254 }
  255 
  256 void
  257 g_cancel_event(void *ref)
  258 {
  259         struct g_event *ep, *epn;
  260         struct g_provider *pp;
  261         u_int n;
  262 
  263         mtx_lock(&g_eventlock);
  264         TAILQ_FOREACH(pp, &g_doorstep, orphan) {
  265                 if (pp != ref)
  266                         continue;
  267                 TAILQ_REMOVE(&g_doorstep, pp, orphan);
  268                 break;
  269         }
  270         TAILQ_FOREACH_SAFE(ep, &g_events, events, epn) {
  271                 if (ep->flag & EV_INPROGRESS)
  272                         continue;
  273                 for (n = 0; n < G_N_EVENTREFS; n++) {
  274                         if (ep->ref[n] == NULL)
  275                                 break;
  276                         if (ep->ref[n] != ref)
  277                                 continue;
  278                         TAILQ_REMOVE(&g_events, ep, events);
  279                         ep->func(ep->arg, EV_CANCEL);
  280                         mtx_assert(&g_eventlock, MA_OWNED);
  281                         if (ep->flag & EV_WAKEUP) {
  282                                 ep->flag |= (EV_DONE|EV_CANCELED);
  283                                 wakeup(ep);
  284                         } else {
  285                                 g_free(ep);
  286                         }
  287                         break;
  288                 }
  289         }
  290         if (TAILQ_EMPTY(&g_events))
  291                 wakeup(&g_pending_events);
  292         mtx_unlock(&g_eventlock);
  293 }
  294 
  295 static int
  296 g_post_event_x(g_event_t *func, void *arg, int flag, int wuflag, struct g_event **epp, va_list ap)
  297 {
  298         struct g_event *ep;
  299         void *p;
  300         u_int n;
  301 
  302         g_trace(G_T_TOPOLOGY, "g_post_event_x(%p, %p, %d, %d)",
  303             func, arg, flag, wuflag);
  304         KASSERT(wuflag == 0 || wuflag == EV_WAKEUP,
  305             ("Wrong wuflag in g_post_event_x(0x%x)", wuflag));
  306         ep = g_malloc(sizeof *ep, flag | M_ZERO);
  307         if (ep == NULL)
  308                 return (ENOMEM);
  309         ep->flag = wuflag;
  310         for (n = 0; n < G_N_EVENTREFS; n++) {
  311                 p = va_arg(ap, void *);
  312                 if (p == NULL)
  313                         break;
  314                 g_trace(G_T_TOPOLOGY, "  ref %p", p);
  315                 ep->ref[n] = p;
  316         }
  317         KASSERT(p == NULL, ("Too many references to event"));
  318         ep->func = func;
  319         ep->arg = arg;
  320         mtx_lock(&g_eventlock);
  321         TAILQ_INSERT_TAIL(&g_events, ep, events);
  322         mtx_unlock(&g_eventlock);
  323         wakeup(&g_wait_event);
  324         if (epp != NULL)
  325                 *epp = ep;
  326         curthread->td_pflags |= TDP_GEOM;
  327         return (0);
  328 }
  329 
  330 int
  331 g_post_event(g_event_t *func, void *arg, int flag, ...)
  332 {
  333         va_list ap;
  334         int i;
  335 
  336         KASSERT(flag == M_WAITOK || flag == M_NOWAIT,
  337             ("Wrong flag to g_post_event"));
  338         va_start(ap, flag);
  339         i = g_post_event_x(func, arg, flag, 0, NULL, ap);
  340         va_end(ap);
  341         return (i);
  342 }
  343 
  344 void
  345 g_do_wither()
  346 {
  347 
  348         mtx_lock(&g_eventlock);
  349         g_wither_work = 1;
  350         mtx_unlock(&g_eventlock);
  351         wakeup(&g_wait_event);
  352 }
  353 
  354 /*
  355  * XXX: It might actually be useful to call this function with topology held.
  356  * XXX: This would ensure that the event gets created before anything else
  357  * XXX: changes.  At present all users have a handle on things in some other
  358  * XXX: way, so this remains an XXX for now.
  359  */
  360 
  361 int
  362 g_waitfor_event(g_event_t *func, void *arg, int flag, ...)
  363 {
  364         va_list ap;
  365         struct g_event *ep;
  366         int error;
  367 
  368         g_topology_assert_not();
  369         KASSERT(flag == M_WAITOK || flag == M_NOWAIT,
  370             ("Wrong flag to g_post_event"));
  371         va_start(ap, flag);
  372         error = g_post_event_x(func, arg, flag, EV_WAKEUP, &ep, ap);
  373         va_end(ap);
  374         if (error)
  375                 return (error);
  376 
  377         mtx_lock(&g_eventlock);
  378         while (!(ep->flag & EV_DONE))
  379                 msleep(ep, &g_eventlock, PRIBIO, "g_waitfor_event", hz);
  380         if (ep->flag & EV_CANCELED)
  381                 error = EAGAIN;
  382         mtx_unlock(&g_eventlock);
  383 
  384         g_free(ep);
  385         return (error);
  386 }
  387 
  388 void
  389 g_event_init()
  390 {
  391 
  392         mtx_init(&g_eventlock, "GEOM orphanage", NULL, MTX_DEF);
  393 }

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