sys/vfs/hammer2/hammer2_ccms.c

   1 /*
   2  * Copyright (c) 2006,2012-2014 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   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  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34 /*
  35  * The Cache Coherency Management System (CCMS)
  36  */
  37
  38 #include <sys/param.h>
  39 #include <sys/systm.h>
  40 #include <sys/kernel.h>
  41 #include <sys/malloc.h>
  42 #include <sys/objcache.h>
  43 #include <sys/sysctl.h>
  44 #include <sys/uio.h>
  45 #include <machine/limits.h>
  46
  47 #include <sys/spinlock2.h>
  48
  49 #include "hammer2_ccms.h"
  50 #include "hammer2.h"
  51
  52 int ccms_debug = 0;
  53
  54 void
  55 ccms_cst_init(ccms_cst_t *cst)
  56 {
  57         bzero(cst, sizeof(*cst));
  58         spin_init(&cst->spin, "ccmscst");
  59 }
  60
  61 void
  62 ccms_cst_uninit(ccms_cst_t *cst)
  63 {
  64         KKASSERT(cst->count == 0);
  65         if (cst->state != CCMS_STATE_INVALID) {
  66                 /* XXX */
  67         }
  68 }
  69
  70 /************************************************************************
  71  *                          CST SUPPORT FUNCTIONS                       *
  72  ************************************************************************/
  73
  74 /*
  75  * Acquire local cache state & lock.  If the current thread already holds
  76  * the lock exclusively we bump the exclusive count, even if the thread is
  77  * trying to get a shared lock.
  78  */
  79 void
  80 ccms_thread_lock(ccms_cst_t *cst, ccms_state_t state)
  81 {
  82         /*
  83          * Regardless of the type of lock requested if the current thread
  84          * already holds an exclusive lock we bump the exclusive count and
  85          * return.  This requires no spinlock.
  86          */
  87         LOCKENTER;
  88         if (cst->count < 0 && cst->td == curthread) {
  89                 --cst->count;
  90                 return;
  91         }
  92
  93         /*
  94          * Otherwise use the spinlock to interlock the operation and sleep
  95          * as necessary.
  96          */
  97         hammer2_spin_ex(&cst->spin);
  98         if (state == CCMS_STATE_SHARED) {
  99                 while (cst->count < 0 || cst->upgrade) {
 100                         cst->blocked = 1;
 101                         ssleep(cst, &cst->spin, 0, "ccmslck", hz);
 102                 }
 103                 ++cst->count;
 104                 KKASSERT(cst->td == NULL);
 105         } else if (state == CCMS_STATE_EXCLUSIVE) {
 106                 while (cst->count != 0 || cst->upgrade) {
 107                         cst->blocked = 1;
 108                         ssleep(cst, &cst->spin, 0, "ccmslck", hz);
 109                 }
 110                 cst->count = -1;
 111                 cst->td = curthread;
 112         } else {
 113                 hammer2_spin_unex(&cst->spin);
 114                 panic("ccms_thread_lock: bad state %d\n", state);
 115         }
 116         hammer2_spin_unex(&cst->spin);
 117 }
 118
 119 /*
 120  * Same as ccms_thread_lock() but acquires the lock non-blocking.  Returns
 121  * 0 on success, EBUSY on failure.
 122  */
 123 int
 124 ccms_thread_lock_nonblock(ccms_cst_t *cst, ccms_state_t state)
 125 {
 126         if (cst->count < 0 && cst->td == curthread) {
 127                 --cst->count;
 128                 LOCKENTER;
 129                 return(0);
 130         }
 131
 132         hammer2_spin_ex(&cst->spin);
 133         if (state == CCMS_STATE_SHARED) {
 134                 if (cst->count < 0 || cst->upgrade) {
 135                         hammer2_spin_unex(&cst->spin);
 136                         return (EBUSY);
 137                 }
 138                 ++cst->count;
 139                 KKASSERT(cst->td == NULL);
 140         } else if (state == CCMS_STATE_EXCLUSIVE) {
 141                 if (cst->count != 0 || cst->upgrade) {
 142                         hammer2_spin_unex(&cst->spin);
 143                         return (EBUSY);
 144                 }
 145                 cst->count = -1;
 146                 cst->td = curthread;
 147         } else {
 148                 hammer2_spin_unex(&cst->spin);
 149                 panic("ccms_thread_lock_nonblock: bad state %d\n", state);
 150         }
 151         hammer2_spin_unex(&cst->spin);
 152         LOCKENTER;
 153         return(0);
 154 }
 155
 156 ccms_state_t
 157 ccms_thread_lock_temp_release(ccms_cst_t *cst)
 158 {
 159         if (cst->count < 0) {
 160                 ccms_thread_unlock(cst);
 161                 return(CCMS_STATE_EXCLUSIVE);
 162         }
 163         if (cst->count > 0) {
 164                 ccms_thread_unlock(cst);
 165                 return(CCMS_STATE_SHARED);
 166         }
 167         return (CCMS_STATE_INVALID);
 168 }
 169
 170 void
 171 ccms_thread_lock_temp_restore(ccms_cst_t *cst, ccms_state_t ostate)
 172 {
 173         ccms_thread_lock(cst, ostate);
 174 }
 175
 176 /*
 177  * Temporarily upgrade a thread lock for making local structural changes.
 178  * No new shared or exclusive locks can be acquired by others while we are
 179  * upgrading, but other upgraders are allowed.
 180  */
 181 ccms_state_t
 182 ccms_thread_lock_upgrade(ccms_cst_t *cst)
 183 {
 184         /*
 185          * Nothing to do if already exclusive
 186          */
 187         if (cst->count < 0) {
 188                 KKASSERT(cst->td == curthread);
 189                 return(CCMS_STATE_EXCLUSIVE);
 190         }
 191
 192         /*
 193          * Convert a shared lock to exclusive.
 194          */
 195         if (cst->count > 0) {
 196                 hammer2_spin_ex(&cst->spin);
 197                 ++cst->upgrade;
 198                 --cst->count;
 199                 while (cst->count) {
 200                         cst->blocked = 1;
 201                         ssleep(cst, &cst->spin, 0, "ccmsupg", hz);
 202                 }
 203                 cst->count = -1;
 204                 cst->td = curthread;
 205                 hammer2_spin_unex(&cst->spin);
 206                 return(CCMS_STATE_SHARED);
 207         }
 208         panic("ccms_thread_lock_upgrade: not locked");
 209         /* NOT REACHED */
 210         return(0);
 211 }
 212
 213 void
 214 ccms_thread_lock_downgrade(ccms_cst_t *cst, ccms_state_t ostate)
 215 {
 216         if (ostate == CCMS_STATE_SHARED) {
 217                 KKASSERT(cst->td == curthread);
 218                 KKASSERT(cst->count == -1);
 219                 hammer2_spin_ex(&cst->spin);
 220                 --cst->upgrade;
 221                 cst->count = 1;
 222                 cst->td = NULL;
 223                 if (cst->blocked) {
 224                         cst->blocked = 0;
 225                         hammer2_spin_unex(&cst->spin);
 226                         wakeup(cst);
 227                 } else {
 228                         hammer2_spin_unex(&cst->spin);
 229                 }
 230         }
 231         /* else nothing to do if excl->excl */
 232 }
 233
 234 /*
 235  * Release a local thread lock
 236  */
 237 void
 238 ccms_thread_unlock(ccms_cst_t *cst)
 239 {
 240         LOCKEXIT;
 241         if (cst->count < 0) {
 242                 /*
 243                  * Exclusive
 244                  */
 245                 KKASSERT(cst->td == curthread);
 246                 if (cst->count < -1) {
 247                         ++cst->count;
 248                         return;
 249                 }
 250                 hammer2_spin_ex(&cst->spin);
 251                 KKASSERT(cst->count == -1);
 252                 cst->count = 0;
 253                 cst->td = NULL;
 254                 if (cst->blocked) {
 255                         cst->blocked = 0;
 256                         hammer2_spin_unex(&cst->spin);
 257                         wakeup(cst);
 258                         return;
 259                 }
 260                 hammer2_spin_unex(&cst->spin);
 261         } else if (cst->count > 0) {
 262                 /*
 263                  * Shared
 264                  */
 265                 hammer2_spin_ex(&cst->spin);
 266                 if (--cst->count == 0 && cst->blocked) {
 267                         cst->blocked = 0;
 268                         hammer2_spin_unex(&cst->spin);
 269                         wakeup(cst);
 270                         return;
 271                 }
 272                 hammer2_spin_unex(&cst->spin);
 273         } else {
 274                 panic("ccms_thread_unlock: bad zero count\n");
 275         }
 276 }
 277
 278 void
 279 ccms_thread_lock_setown(ccms_cst_t *cst)
 280 {
 281         KKASSERT(cst->count < 0);
 282         cst->td = curthread;
 283 }
 284
 285 /*
 286  * Release a previously upgraded local thread lock
 287  */
 288 void
 289 ccms_thread_unlock_upgraded(ccms_cst_t *cst, ccms_state_t ostate)
 290 {
 291         if (ostate == CCMS_STATE_SHARED) {
 292                 LOCKEXIT;
 293                 KKASSERT(cst->td == curthread);
 294                 KKASSERT(cst->count == -1);
 295                 hammer2_spin_ex(&cst->spin);
 296                 --cst->upgrade;
 297                 cst->count = 0;
 298                 cst->td = NULL;
 299                 if (cst->blocked) {
 300                         cst->blocked = 0;
 301                         hammer2_spin_unex(&cst->spin);
 302                         wakeup(cst);
 303                 } else {
 304                         hammer2_spin_unex(&cst->spin);
 305                 }
 306         } else {
 307                 ccms_thread_unlock(cst);
 308         }
 309 }
 310
 311 int
 312 ccms_thread_lock_owned(ccms_cst_t *cst)
 313 {
 314         return(cst->count < 0 && cst->td == curthread);
 315 }