kern_rmlock.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-3-Clause
    3  *
    4  * Copyright (c) 2007 Stephan Uphoff <ups@FreeBSD.org>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  * 3. Neither the name of the author nor the names of any co-contributors
   16  *    may be used to endorse or promote products derived from this software
   17  *    without specific prior written permission.
   18  *
   19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   29  * SUCH DAMAGE.
   30  */
   31 
   32 /*
   33  * Machine independent bits of reader/writer lock implementation.
   34  */
   35 
   36 #include <sys/cdefs.h>
   37 __FBSDID("$FreeBSD: releng/12.0/sys/kern/kern_rmlock.c 334546 2018-06-02 22:37:53Z mjg $");
   38 
   39 #include "opt_ddb.h"
   40 
   41 #include <sys/param.h>
   42 #include <sys/systm.h>
   43 
   44 #include <sys/kernel.h>
   45 #include <sys/kdb.h>
   46 #include <sys/ktr.h>
   47 #include <sys/lock.h>
   48 #include <sys/mutex.h>
   49 #include <sys/proc.h>
   50 #include <sys/rmlock.h>
   51 #include <sys/sched.h>
   52 #include <sys/smp.h>
   53 #include <sys/turnstile.h>
   54 #include <sys/lock_profile.h>
   55 #include <machine/cpu.h>
   56 
   57 #ifdef DDB
   58 #include <ddb/ddb.h>
   59 #endif
   60 
   61 /*
   62  * A cookie to mark destroyed rmlocks.  This is stored in the head of
   63  * rm_activeReaders.
   64  */
   65 #define RM_DESTROYED    ((void *)0xdead)
   66 
   67 #define rm_destroyed(rm)                                                \
   68         (LIST_FIRST(&(rm)->rm_activeReaders) == RM_DESTROYED)
   69 
   70 #define RMPF_ONQUEUE    1
   71 #define RMPF_SIGNAL     2
   72 
   73 #ifndef INVARIANTS
   74 #define _rm_assert(c, what, file, line)
   75 #endif
   76 
   77 static void     assert_rm(const struct lock_object *lock, int what);
   78 #ifdef DDB
   79 static void     db_show_rm(const struct lock_object *lock);
   80 #endif
   81 static void     lock_rm(struct lock_object *lock, uintptr_t how);
   82 #ifdef KDTRACE_HOOKS
   83 static int      owner_rm(const struct lock_object *lock, struct thread **owner);
   84 #endif
   85 static uintptr_t unlock_rm(struct lock_object *lock);
   86 
   87 struct lock_class lock_class_rm = {
   88         .lc_name = "rm",
   89         .lc_flags = LC_SLEEPLOCK | LC_RECURSABLE,
   90         .lc_assert = assert_rm,
   91 #ifdef DDB
   92         .lc_ddb_show = db_show_rm,
   93 #endif
   94         .lc_lock = lock_rm,
   95         .lc_unlock = unlock_rm,
   96 #ifdef KDTRACE_HOOKS
   97         .lc_owner = owner_rm,
   98 #endif
   99 };
  100 
  101 struct lock_class lock_class_rm_sleepable = {
  102         .lc_name = "sleepable rm",
  103         .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE,
  104         .lc_assert = assert_rm,
  105 #ifdef DDB
  106         .lc_ddb_show = db_show_rm,
  107 #endif
  108         .lc_lock = lock_rm,
  109         .lc_unlock = unlock_rm,
  110 #ifdef KDTRACE_HOOKS
  111         .lc_owner = owner_rm,
  112 #endif
  113 };
  114 
  115 static void
  116 assert_rm(const struct lock_object *lock, int what)
  117 {
  118 
  119         rm_assert((const struct rmlock *)lock, what);
  120 }
  121 
  122 static void
  123 lock_rm(struct lock_object *lock, uintptr_t how)
  124 {
  125         struct rmlock *rm;
  126         struct rm_priotracker *tracker;
  127 
  128         rm = (struct rmlock *)lock;
  129         if (how == 0)
  130                 rm_wlock(rm);
  131         else {
  132                 tracker = (struct rm_priotracker *)how;
  133                 rm_rlock(rm, tracker);
  134         }
  135 }
  136 
  137 static uintptr_t
  138 unlock_rm(struct lock_object *lock)
  139 {
  140         struct thread *td;
  141         struct pcpu *pc;
  142         struct rmlock *rm;
  143         struct rm_queue *queue;
  144         struct rm_priotracker *tracker;
  145         uintptr_t how;
  146 
  147         rm = (struct rmlock *)lock;
  148         tracker = NULL;
  149         how = 0;
  150         rm_assert(rm, RA_LOCKED | RA_NOTRECURSED);
  151         if (rm_wowned(rm))
  152                 rm_wunlock(rm);
  153         else {
  154                 /*
  155                  * Find the right rm_priotracker structure for curthread.
  156                  * The guarantee about its uniqueness is given by the fact
  157                  * we already asserted the lock wasn't recursively acquired.
  158                  */
  159                 critical_enter();
  160                 td = curthread;
  161                 pc = get_pcpu();
  162                 for (queue = pc->pc_rm_queue.rmq_next;
  163                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
  164                         tracker = (struct rm_priotracker *)queue;
  165                                 if ((tracker->rmp_rmlock == rm) &&
  166                                     (tracker->rmp_thread == td)) {
  167                                         how = (uintptr_t)tracker;
  168                                         break;
  169                                 }
  170                 }
  171                 KASSERT(tracker != NULL,
  172                     ("rm_priotracker is non-NULL when lock held in read mode"));
  173                 critical_exit();
  174                 rm_runlock(rm, tracker);
  175         }
  176         return (how);
  177 }
  178 
  179 #ifdef KDTRACE_HOOKS
  180 static int
  181 owner_rm(const struct lock_object *lock, struct thread **owner)
  182 {
  183         const struct rmlock *rm;
  184         struct lock_class *lc;
  185 
  186         rm = (const struct rmlock *)lock;
  187         lc = LOCK_CLASS(&rm->rm_wlock_object);
  188         return (lc->lc_owner(&rm->rm_wlock_object, owner));
  189 }
  190 #endif
  191 
  192 static struct mtx rm_spinlock;
  193 
  194 MTX_SYSINIT(rm_spinlock, &rm_spinlock, "rm_spinlock", MTX_SPIN);
  195 
  196 /*
  197  * Add or remove tracker from per-cpu list.
  198  *
  199  * The per-cpu list can be traversed at any time in forward direction from an
  200  * interrupt on the *local* cpu.
  201  */
  202 static void inline
  203 rm_tracker_add(struct pcpu *pc, struct rm_priotracker *tracker)
  204 {
  205         struct rm_queue *next;
  206 
  207         /* Initialize all tracker pointers */
  208         tracker->rmp_cpuQueue.rmq_prev = &pc->pc_rm_queue;
  209         next = pc->pc_rm_queue.rmq_next;
  210         tracker->rmp_cpuQueue.rmq_next = next;
  211 
  212         /* rmq_prev is not used during froward traversal. */
  213         next->rmq_prev = &tracker->rmp_cpuQueue;
  214 
  215         /* Update pointer to first element. */
  216         pc->pc_rm_queue.rmq_next = &tracker->rmp_cpuQueue;
  217 }
  218 
  219 /*
  220  * Return a count of the number of trackers the thread 'td' already
  221  * has on this CPU for the lock 'rm'.
  222  */
  223 static int
  224 rm_trackers_present(const struct pcpu *pc, const struct rmlock *rm,
  225     const struct thread *td)
  226 {
  227         struct rm_queue *queue;
  228         struct rm_priotracker *tracker;
  229         int count;
  230 
  231         count = 0;
  232         for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue;
  233             queue = queue->rmq_next) {
  234                 tracker = (struct rm_priotracker *)queue;
  235                 if ((tracker->rmp_rmlock == rm) && (tracker->rmp_thread == td))
  236                         count++;
  237         }
  238         return (count);
  239 }
  240 
  241 static void inline
  242 rm_tracker_remove(struct pcpu *pc, struct rm_priotracker *tracker)
  243 {
  244         struct rm_queue *next, *prev;
  245 
  246         next = tracker->rmp_cpuQueue.rmq_next;
  247         prev = tracker->rmp_cpuQueue.rmq_prev;
  248 
  249         /* Not used during forward traversal. */
  250         next->rmq_prev = prev;
  251 
  252         /* Remove from list. */
  253         prev->rmq_next = next;
  254 }
  255 
  256 static void
  257 rm_cleanIPI(void *arg)
  258 {
  259         struct pcpu *pc;
  260         struct rmlock *rm = arg;
  261         struct rm_priotracker *tracker;
  262         struct rm_queue *queue;
  263         pc = get_pcpu();
  264 
  265         for (queue = pc->pc_rm_queue.rmq_next; queue != &pc->pc_rm_queue;
  266             queue = queue->rmq_next) {
  267                 tracker = (struct rm_priotracker *)queue;
  268                 if (tracker->rmp_rmlock == rm && tracker->rmp_flags == 0) {
  269                         tracker->rmp_flags = RMPF_ONQUEUE;
  270                         mtx_lock_spin(&rm_spinlock);
  271                         LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker,
  272                             rmp_qentry);
  273                         mtx_unlock_spin(&rm_spinlock);
  274                 }
  275         }
  276 }
  277 
  278 void
  279 rm_init_flags(struct rmlock *rm, const char *name, int opts)
  280 {
  281         struct lock_class *lc;
  282         int liflags, xflags;
  283 
  284         liflags = 0;
  285         if (!(opts & RM_NOWITNESS))
  286                 liflags |= LO_WITNESS;
  287         if (opts & RM_RECURSE)
  288                 liflags |= LO_RECURSABLE;
  289         if (opts & RM_NEW)
  290                 liflags |= LO_NEW;
  291         rm->rm_writecpus = all_cpus;
  292         LIST_INIT(&rm->rm_activeReaders);
  293         if (opts & RM_SLEEPABLE) {
  294                 liflags |= LO_SLEEPABLE;
  295                 lc = &lock_class_rm_sleepable;
  296                 xflags = (opts & RM_NEW ? SX_NEW : 0);
  297                 sx_init_flags(&rm->rm_lock_sx, "rmlock_sx",
  298                     xflags | SX_NOWITNESS);
  299         } else {
  300                 lc = &lock_class_rm;
  301                 xflags = (opts & RM_NEW ? MTX_NEW : 0);
  302                 mtx_init(&rm->rm_lock_mtx, name, "rmlock_mtx",
  303                     xflags | MTX_NOWITNESS);
  304         }
  305         lock_init(&rm->lock_object, lc, name, NULL, liflags);
  306 }
  307 
  308 void
  309 rm_init(struct rmlock *rm, const char *name)
  310 {
  311 
  312         rm_init_flags(rm, name, 0);
  313 }
  314 
  315 void
  316 rm_destroy(struct rmlock *rm)
  317 {
  318 
  319         rm_assert(rm, RA_UNLOCKED);
  320         LIST_FIRST(&rm->rm_activeReaders) = RM_DESTROYED;
  321         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  322                 sx_destroy(&rm->rm_lock_sx);
  323         else
  324                 mtx_destroy(&rm->rm_lock_mtx);
  325         lock_destroy(&rm->lock_object);
  326 }
  327 
  328 int
  329 rm_wowned(const struct rmlock *rm)
  330 {
  331 
  332         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  333                 return (sx_xlocked(&rm->rm_lock_sx));
  334         else
  335                 return (mtx_owned(&rm->rm_lock_mtx));
  336 }
  337 
  338 void
  339 rm_sysinit(void *arg)
  340 {
  341         struct rm_args *args;
  342 
  343         args = arg;
  344         rm_init_flags(args->ra_rm, args->ra_desc, args->ra_flags);
  345 }
  346 
  347 static __noinline int
  348 _rm_rlock_hard(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
  349 {
  350         struct pcpu *pc;
  351 
  352         critical_enter();
  353         pc = get_pcpu();
  354 
  355         /* Check if we just need to do a proper critical_exit. */
  356         if (!CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus)) {
  357                 critical_exit();
  358                 return (1);
  359         }
  360 
  361         /* Remove our tracker from the per-cpu list. */
  362         rm_tracker_remove(pc, tracker);
  363 
  364         /* Check to see if the IPI granted us the lock after all. */
  365         if (tracker->rmp_flags) {
  366                 /* Just add back tracker - we hold the lock. */
  367                 rm_tracker_add(pc, tracker);
  368                 critical_exit();
  369                 return (1);
  370         }
  371 
  372         /*
  373          * We allow readers to acquire a lock even if a writer is blocked if
  374          * the lock is recursive and the reader already holds the lock.
  375          */
  376         if ((rm->lock_object.lo_flags & LO_RECURSABLE) != 0) {
  377                 /*
  378                  * Just grant the lock if this thread already has a tracker
  379                  * for this lock on the per-cpu queue.
  380                  */
  381                 if (rm_trackers_present(pc, rm, curthread) != 0) {
  382                         mtx_lock_spin(&rm_spinlock);
  383                         LIST_INSERT_HEAD(&rm->rm_activeReaders, tracker,
  384                             rmp_qentry);
  385                         tracker->rmp_flags = RMPF_ONQUEUE;
  386                         mtx_unlock_spin(&rm_spinlock);
  387                         rm_tracker_add(pc, tracker);
  388                         critical_exit();
  389                         return (1);
  390                 }
  391         }
  392 
  393         sched_unpin();
  394         critical_exit();
  395 
  396         if (trylock) {
  397                 if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
  398                         if (!sx_try_xlock(&rm->rm_lock_sx))
  399                                 return (0);
  400                 } else {
  401                         if (!mtx_trylock(&rm->rm_lock_mtx))
  402                                 return (0);
  403                 }
  404         } else {
  405                 if (rm->lock_object.lo_flags & LO_SLEEPABLE) {
  406                         THREAD_SLEEPING_OK();
  407                         sx_xlock(&rm->rm_lock_sx);
  408                         THREAD_NO_SLEEPING();
  409                 } else
  410                         mtx_lock(&rm->rm_lock_mtx);
  411         }
  412 
  413         critical_enter();
  414         pc = get_pcpu();
  415         CPU_CLR(pc->pc_cpuid, &rm->rm_writecpus);
  416         rm_tracker_add(pc, tracker);
  417         sched_pin();
  418         critical_exit();
  419 
  420         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  421                 sx_xunlock(&rm->rm_lock_sx);
  422         else
  423                 mtx_unlock(&rm->rm_lock_mtx);
  424 
  425         return (1);
  426 }
  427 
  428 int
  429 _rm_rlock(struct rmlock *rm, struct rm_priotracker *tracker, int trylock)
  430 {
  431         struct thread *td = curthread;
  432         struct pcpu *pc;
  433 
  434         if (SCHEDULER_STOPPED())
  435                 return (1);
  436 
  437         tracker->rmp_flags  = 0;
  438         tracker->rmp_thread = td;
  439         tracker->rmp_rmlock = rm;
  440 
  441         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  442                 THREAD_NO_SLEEPING();
  443 
  444         td->td_critnest++;      /* critical_enter(); */
  445 
  446         __compiler_membar();
  447 
  448         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
  449 
  450         rm_tracker_add(pc, tracker);
  451 
  452         sched_pin();
  453 
  454         __compiler_membar();
  455 
  456         td->td_critnest--;
  457 
  458         /*
  459          * Fast path to combine two common conditions into a single
  460          * conditional jump.
  461          */
  462         if (__predict_true(0 == (td->td_owepreempt |
  463             CPU_ISSET(pc->pc_cpuid, &rm->rm_writecpus))))
  464                 return (1);
  465 
  466         /* We do not have a read token and need to acquire one. */
  467         return _rm_rlock_hard(rm, tracker, trylock);
  468 }
  469 
  470 static __noinline void
  471 _rm_unlock_hard(struct thread *td,struct rm_priotracker *tracker)
  472 {
  473 
  474         if (td->td_owepreempt) {
  475                 td->td_critnest++;
  476                 critical_exit();
  477         }
  478 
  479         if (!tracker->rmp_flags)
  480                 return;
  481 
  482         mtx_lock_spin(&rm_spinlock);
  483         LIST_REMOVE(tracker, rmp_qentry);
  484 
  485         if (tracker->rmp_flags & RMPF_SIGNAL) {
  486                 struct rmlock *rm;
  487                 struct turnstile *ts;
  488 
  489                 rm = tracker->rmp_rmlock;
  490 
  491                 turnstile_chain_lock(&rm->lock_object);
  492                 mtx_unlock_spin(&rm_spinlock);
  493 
  494                 ts = turnstile_lookup(&rm->lock_object);
  495 
  496                 turnstile_signal(ts, TS_EXCLUSIVE_QUEUE);
  497                 turnstile_unpend(ts);
  498                 turnstile_chain_unlock(&rm->lock_object);
  499         } else
  500                 mtx_unlock_spin(&rm_spinlock);
  501 }
  502 
  503 void
  504 _rm_runlock(struct rmlock *rm, struct rm_priotracker *tracker)
  505 {
  506         struct pcpu *pc;
  507         struct thread *td = tracker->rmp_thread;
  508 
  509         if (SCHEDULER_STOPPED())
  510                 return;
  511 
  512         td->td_critnest++;      /* critical_enter(); */
  513         pc = cpuid_to_pcpu[td->td_oncpu]; /* pcpu_find(td->td_oncpu); */
  514         rm_tracker_remove(pc, tracker);
  515         td->td_critnest--;
  516         sched_unpin();
  517 
  518         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  519                 THREAD_SLEEPING_OK();
  520 
  521         if (__predict_true(0 == (td->td_owepreempt | tracker->rmp_flags)))
  522                 return;
  523 
  524         _rm_unlock_hard(td, tracker);
  525 }
  526 
  527 void
  528 _rm_wlock(struct rmlock *rm)
  529 {
  530         struct rm_priotracker *prio;
  531         struct turnstile *ts;
  532         cpuset_t readcpus;
  533 
  534         if (SCHEDULER_STOPPED())
  535                 return;
  536 
  537         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  538                 sx_xlock(&rm->rm_lock_sx);
  539         else
  540                 mtx_lock(&rm->rm_lock_mtx);
  541 
  542         if (CPU_CMP(&rm->rm_writecpus, &all_cpus)) {
  543                 /* Get all read tokens back */
  544                 readcpus = all_cpus;
  545                 CPU_NAND(&readcpus, &rm->rm_writecpus);
  546                 rm->rm_writecpus = all_cpus;
  547 
  548                 /*
  549                  * Assumes rm->rm_writecpus update is visible on other CPUs
  550                  * before rm_cleanIPI is called.
  551                  */
  552 #ifdef SMP
  553                 smp_rendezvous_cpus(readcpus,
  554                     smp_no_rendezvous_barrier,
  555                     rm_cleanIPI,
  556                     smp_no_rendezvous_barrier,
  557                     rm);
  558 
  559 #else
  560                 rm_cleanIPI(rm);
  561 #endif
  562 
  563                 mtx_lock_spin(&rm_spinlock);
  564                 while ((prio = LIST_FIRST(&rm->rm_activeReaders)) != NULL) {
  565                         ts = turnstile_trywait(&rm->lock_object);
  566                         prio->rmp_flags = RMPF_ONQUEUE | RMPF_SIGNAL;
  567                         mtx_unlock_spin(&rm_spinlock);
  568                         turnstile_wait(ts, prio->rmp_thread,
  569                             TS_EXCLUSIVE_QUEUE);
  570                         mtx_lock_spin(&rm_spinlock);
  571                 }
  572                 mtx_unlock_spin(&rm_spinlock);
  573         }
  574 }
  575 
  576 void
  577 _rm_wunlock(struct rmlock *rm)
  578 {
  579 
  580         if (rm->lock_object.lo_flags & LO_SLEEPABLE)
  581                 sx_xunlock(&rm->rm_lock_sx);
  582         else
  583                 mtx_unlock(&rm->rm_lock_mtx);
  584 }
  585 
  586 #if LOCK_DEBUG > 0
  587 
  588 void
  589 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
  590 {
  591 
  592         if (SCHEDULER_STOPPED())
  593                 return;
  594 
  595         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
  596             ("rm_wlock() by idle thread %p on rmlock %s @ %s:%d",
  597             curthread, rm->lock_object.lo_name, file, line));
  598         KASSERT(!rm_destroyed(rm),
  599             ("rm_wlock() of destroyed rmlock @ %s:%d", file, line));
  600         _rm_assert(rm, RA_UNLOCKED, file, line);
  601 
  602         WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE,
  603             file, line, NULL);
  604 
  605         _rm_wlock(rm);
  606 
  607         LOCK_LOG_LOCK("RMWLOCK", &rm->lock_object, 0, 0, file, line);
  608         WITNESS_LOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
  609         TD_LOCKS_INC(curthread);
  610 }
  611 
  612 void
  613 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
  614 {
  615 
  616         if (SCHEDULER_STOPPED())
  617                 return;
  618 
  619         KASSERT(!rm_destroyed(rm),
  620             ("rm_wunlock() of destroyed rmlock @ %s:%d", file, line));
  621         _rm_assert(rm, RA_WLOCKED, file, line);
  622         WITNESS_UNLOCK(&rm->lock_object, LOP_EXCLUSIVE, file, line);
  623         LOCK_LOG_LOCK("RMWUNLOCK", &rm->lock_object, 0, 0, file, line);
  624         _rm_wunlock(rm);
  625         TD_LOCKS_DEC(curthread);
  626 }
  627 
  628 int
  629 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
  630     int trylock, const char *file, int line)
  631 {
  632 
  633         if (SCHEDULER_STOPPED())
  634                 return (1);
  635 
  636 #ifdef INVARIANTS
  637         if (!(rm->lock_object.lo_flags & LO_RECURSABLE) && !trylock) {
  638                 critical_enter();
  639                 KASSERT(rm_trackers_present(get_pcpu(), rm,
  640                     curthread) == 0,
  641                     ("rm_rlock: recursed on non-recursive rmlock %s @ %s:%d\n",
  642                     rm->lock_object.lo_name, file, line));
  643                 critical_exit();
  644         }
  645 #endif
  646         KASSERT(kdb_active != 0 || !TD_IS_IDLETHREAD(curthread),
  647             ("rm_rlock() by idle thread %p on rmlock %s @ %s:%d",
  648             curthread, rm->lock_object.lo_name, file, line));
  649         KASSERT(!rm_destroyed(rm),
  650             ("rm_rlock() of destroyed rmlock @ %s:%d", file, line));
  651         if (!trylock) {
  652                 KASSERT(!rm_wowned(rm),
  653                     ("rm_rlock: wlock already held for %s @ %s:%d",
  654                     rm->lock_object.lo_name, file, line));
  655                 WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line,
  656                     NULL);
  657         }
  658 
  659         if (_rm_rlock(rm, tracker, trylock)) {
  660                 if (trylock)
  661                         LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 1, file,
  662                             line);
  663                 else
  664                         LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file,
  665                             line);
  666                 WITNESS_LOCK(&rm->lock_object, 0, file, line);
  667                 TD_LOCKS_INC(curthread);
  668                 return (1);
  669         } else if (trylock)
  670                 LOCK_LOG_TRY("RMRLOCK", &rm->lock_object, 0, 0, file, line);
  671 
  672         return (0);
  673 }
  674 
  675 void
  676 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
  677     const char *file, int line)
  678 {
  679 
  680         if (SCHEDULER_STOPPED())
  681                 return;
  682 
  683         KASSERT(!rm_destroyed(rm),
  684             ("rm_runlock() of destroyed rmlock @ %s:%d", file, line));
  685         _rm_assert(rm, RA_RLOCKED, file, line);
  686         WITNESS_UNLOCK(&rm->lock_object, 0, file, line);
  687         LOCK_LOG_LOCK("RMRUNLOCK", &rm->lock_object, 0, 0, file, line);
  688         _rm_runlock(rm, tracker);
  689         TD_LOCKS_DEC(curthread);
  690 }
  691 
  692 #else
  693 
  694 /*
  695  * Just strip out file and line arguments if no lock debugging is enabled in
  696  * the kernel - we are called from a kernel module.
  697  */
  698 void
  699 _rm_wlock_debug(struct rmlock *rm, const char *file, int line)
  700 {
  701 
  702         _rm_wlock(rm);
  703 }
  704 
  705 void
  706 _rm_wunlock_debug(struct rmlock *rm, const char *file, int line)
  707 {
  708 
  709         _rm_wunlock(rm);
  710 }
  711 
  712 int
  713 _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
  714     int trylock, const char *file, int line)
  715 {
  716 
  717         return _rm_rlock(rm, tracker, trylock);
  718 }
  719 
  720 void
  721 _rm_runlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
  722     const char *file, int line)
  723 {
  724 
  725         _rm_runlock(rm, tracker);
  726 }
  727 
  728 #endif
  729 
  730 #ifdef INVARIANT_SUPPORT
  731 #ifndef INVARIANTS
  732 #undef _rm_assert
  733 #endif
  734 
  735 /*
  736  * Note that this does not need to use witness_assert() for read lock
  737  * assertions since an exact count of read locks held by this thread
  738  * is computable.
  739  */
  740 void
  741 _rm_assert(const struct rmlock *rm, int what, const char *file, int line)
  742 {
  743         int count;
  744 
  745         if (panicstr != NULL)
  746                 return;
  747         switch (what) {
  748         case RA_LOCKED:
  749         case RA_LOCKED | RA_RECURSED:
  750         case RA_LOCKED | RA_NOTRECURSED:
  751         case RA_RLOCKED:
  752         case RA_RLOCKED | RA_RECURSED:
  753         case RA_RLOCKED | RA_NOTRECURSED:
  754                 /*
  755                  * Handle the write-locked case.  Unlike other
  756                  * primitives, writers can never recurse.
  757                  */
  758                 if (rm_wowned(rm)) {
  759                         if (what & RA_RLOCKED)
  760                                 panic("Lock %s exclusively locked @ %s:%d\n",
  761                                     rm->lock_object.lo_name, file, line);
  762                         if (what & RA_RECURSED)
  763                                 panic("Lock %s not recursed @ %s:%d\n",
  764                                     rm->lock_object.lo_name, file, line);
  765                         break;
  766                 }
  767 
  768                 critical_enter();
  769                 count = rm_trackers_present(get_pcpu(), rm, curthread);
  770                 critical_exit();
  771 
  772                 if (count == 0)
  773                         panic("Lock %s not %slocked @ %s:%d\n",
  774                             rm->lock_object.lo_name, (what & RA_RLOCKED) ?
  775                             "read " : "", file, line);
  776                 if (count > 1) {
  777                         if (what & RA_NOTRECURSED)
  778                                 panic("Lock %s recursed @ %s:%d\n",
  779                                     rm->lock_object.lo_name, file, line);
  780                 } else if (what & RA_RECURSED)
  781                         panic("Lock %s not recursed @ %s:%d\n",
  782                             rm->lock_object.lo_name, file, line);
  783                 break;
  784         case RA_WLOCKED:
  785                 if (!rm_wowned(rm))
  786                         panic("Lock %s not exclusively locked @ %s:%d\n",
  787                             rm->lock_object.lo_name, file, line);
  788                 break;
  789         case RA_UNLOCKED:
  790                 if (rm_wowned(rm))
  791                         panic("Lock %s exclusively locked @ %s:%d\n",
  792                             rm->lock_object.lo_name, file, line);
  793 
  794                 critical_enter();
  795                 count = rm_trackers_present(get_pcpu(), rm, curthread);
  796                 critical_exit();
  797 
  798                 if (count != 0)
  799                         panic("Lock %s read locked @ %s:%d\n",
  800                             rm->lock_object.lo_name, file, line);
  801                 break;
  802         default:
  803                 panic("Unknown rm lock assertion: %d @ %s:%d", what, file,
  804                     line);
  805         }
  806 }
  807 #endif /* INVARIANT_SUPPORT */
  808 
  809 #ifdef DDB
  810 static void
  811 print_tracker(struct rm_priotracker *tr)
  812 {
  813         struct thread *td;
  814 
  815         td = tr->rmp_thread;
  816         db_printf("   thread %p (tid %d, pid %d, \"%s\") {", td, td->td_tid,
  817             td->td_proc->p_pid, td->td_name);
  818         if (tr->rmp_flags & RMPF_ONQUEUE) {
  819                 db_printf("ONQUEUE");
  820                 if (tr->rmp_flags & RMPF_SIGNAL)
  821                         db_printf(",SIGNAL");
  822         } else
  823                 db_printf("");
  824         db_printf("}\n");
  825 }
  826 
  827 static void
  828 db_show_rm(const struct lock_object *lock)
  829 {
  830         struct rm_priotracker *tr;
  831         struct rm_queue *queue;
  832         const struct rmlock *rm;
  833         struct lock_class *lc;
  834         struct pcpu *pc;
  835 
  836         rm = (const struct rmlock *)lock;
  837         db_printf(" writecpus: ");
  838         ddb_display_cpuset(__DEQUALIFY(const cpuset_t *, &rm->rm_writecpus));
  839         db_printf("\n");
  840         db_printf(" per-CPU readers:\n");
  841         STAILQ_FOREACH(pc, &cpuhead, pc_allcpu)
  842                 for (queue = pc->pc_rm_queue.rmq_next;
  843                     queue != &pc->pc_rm_queue; queue = queue->rmq_next) {
  844                         tr = (struct rm_priotracker *)queue;
  845                         if (tr->rmp_rmlock == rm)
  846                                 print_tracker(tr);
  847                 }
  848         db_printf(" active readers:\n");
  849         LIST_FOREACH(tr, &rm->rm_activeReaders, rmp_qentry)
  850                 print_tracker(tr);
  851         lc = LOCK_CLASS(&rm->rm_wlock_object);
  852         db_printf("Backing write-lock (%s):\n", lc->lc_name);
  853         lc->lc_ddb_show(&rm->rm_wlock_object);
  854 }
  855 #endif
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FreeBSD/Linux Kernel Cross Reference sys/kern/kern_rmlock.c

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