LCOV - app.info - nsprpub/pr/src/threads/prcmon.c

LCOV - code coverage report
| Current view: | directory - nsprpub/pr/src/threads - prcmon.c (source / functions) |  | Found | Hit | Coverage |
| Test: | app.info | Lines: | 154 | 51 | 33.1 %
| Date: | 2012-04-21 | Functions: | 11 | 3 | 27.3 %

           1                 : /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
           2                 : /* ***** BEGIN LICENSE BLOCK *****
           3                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
           4                 :  *
           5                 :  * The contents of this file are subject to the Mozilla Public License Version
           6                 :  * 1.1 (the "License"); you may not use this file except in compliance with
           7                 :  * the License. You may obtain a copy of the License at
           8                 :  * http://www.mozilla.org/MPL/
           9                 :  *
          10                 :  * Software distributed under the License is distributed on an "AS IS" basis,
          11                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
          12                 :  * for the specific language governing rights and limitations under the
          13                 :  * License.
          14                 :  *
          15                 :  * The Original Code is the Netscape Portable Runtime (NSPR).
          16                 :  *
          17                 :  * The Initial Developer of the Original Code is
          18                 :  * Netscape Communications Corporation.
          19                 :  * Portions created by the Initial Developer are Copyright (C) 1998-2000
          20                 :  * the Initial Developer. All Rights Reserved.
          21                 :  *
          22                 :  * Contributor(s):
          23                 :  *
          24                 :  * Alternatively, the contents of this file may be used under the terms of
          25                 :  * either the GNU General Public License Version 2 or later (the "GPL"), or
          26                 :  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
          27                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
          28                 :  * of those above. If you wish to allow use of your version of this file only
          29                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
          30                 :  * use your version of this file under the terms of the MPL, indicate your
          31                 :  * decision by deleting the provisions above and replace them with the notice
          32                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
          33                 :  * the provisions above, a recipient may use your version of this file under
          34                 :  * the terms of any one of the MPL, the GPL or the LGPL.
          35                 :  *
          36                 :  * ***** END LICENSE BLOCK ***** */
          37                 :
          38                 : #include "primpl.h"
          39                 :
          40                 : #include <stdlib.h>
          41                 : #include <stddef.h>
          42                 :
          43                 : /* Lock used to lock the monitor cache */
          44                 : #ifdef _PR_NO_PREEMPT
          45                 : #define _PR_NEW_LOCK_MCACHE()
          46                 : #define _PR_DESTROY_LOCK_MCACHE()
          47                 : #define _PR_LOCK_MCACHE()
          48                 : #define _PR_UNLOCK_MCACHE()
          49                 : #else
          50                 : #ifdef _PR_LOCAL_THREADS_ONLY
          51                 : #define _PR_NEW_LOCK_MCACHE()
          52                 : #define _PR_DESTROY_LOCK_MCACHE()
          53                 : #define _PR_LOCK_MCACHE() { PRIntn _is; _PR_INTSOFF(_is)
          54                 : #define _PR_UNLOCK_MCACHE() _PR_INTSON(_is); }
          55                 : #else
          56                 : PRLock *_pr_mcacheLock;
          57                 : #define _PR_NEW_LOCK_MCACHE() (_pr_mcacheLock = PR_NewLock())
          58                 : #define _PR_DESTROY_LOCK_MCACHE()               \
          59                 :     PR_BEGIN_MACRO                              \
          60                 :         if (_pr_mcacheLock) {                   \
          61                 :             PR_DestroyLock(_pr_mcacheLock);     \
          62                 :             _pr_mcacheLock = NULL;              \
          63                 :         }                                       \
          64                 :     PR_END_MACRO
          65                 : #define _PR_LOCK_MCACHE() PR_Lock(_pr_mcacheLock)
          66                 : #define _PR_UNLOCK_MCACHE() PR_Unlock(_pr_mcacheLock)
          67                 : #endif
          68                 : #endif
          69                 :
          70                 : /************************************************************************/
          71                 :
          72                 : typedef struct MonitorCacheEntryStr MonitorCacheEntry;
          73                 :
          74                 : struct MonitorCacheEntryStr {
          75                 :     MonitorCacheEntry*  next;
          76                 :     void*               address;
          77                 :     PRMonitor*          mon;
          78                 :     long                cacheEntryCount;
          79                 : };
          80                 :
          81                 : /*
          82                 : ** An array of MonitorCacheEntry's, plus a pointer to link these
          83                 : ** arrays together.
          84                 : */
          85                 :
          86                 : typedef struct MonitorCacheEntryBlockStr MonitorCacheEntryBlock;
          87                 :
          88                 : struct MonitorCacheEntryBlockStr {
          89                 :     MonitorCacheEntryBlock* next;
          90                 :     MonitorCacheEntry entries[1];
          91                 : };
          92                 :
          93                 : static PRUint32 hash_mask;
          94                 : static PRUintn num_hash_buckets;
          95                 : static PRUintn num_hash_buckets_log2;
          96                 : static MonitorCacheEntry **hash_buckets;
          97                 : static MonitorCacheEntry *free_entries;
          98                 : static PRUintn num_free_entries;
          99                 : static PRBool expanding;
         100                 : static MonitorCacheEntryBlock *mcache_blocks;
         101                 :
         102                 : static void (*OnMonitorRecycle)(void *address);
         103                 :
         104                 : #define HASH(address)                               \
         105                 :     ((PRUint32) ( ((PRUptrdiff)(address) >> 2) ^    \
         106                 :                   ((PRUptrdiff)(address) >> 10) )   \
         107                 :      & hash_mask)
         108                 :
         109                 : /*
         110                 : ** Expand the monitor cache. This grows the hash buckets and allocates a
         111                 : ** new chunk of cache entries and throws them on the free list. We keep
         112                 : ** as many hash buckets as there are entries.
         113                 : **
         114                 : ** Because we call malloc and malloc may need the monitor cache, we must
         115                 : ** ensure that there are several free monitor cache entries available for
         116                 : ** malloc to get. FREE_THRESHOLD is used to prevent monitor cache
         117                 : ** starvation during monitor cache expansion.
         118                 : */
         119                 :
         120                 : #define FREE_THRESHOLD  5
         121                 :
         122           19965 : static PRStatus ExpandMonitorCache(PRUintn new_size_log2)
         123                 : {
         124                 :     MonitorCacheEntry **old_hash_buckets, *p;
         125                 :     PRUintn i, entries, old_num_hash_buckets, added;
         126                 :     MonitorCacheEntry **new_hash_buckets;
         127                 :     MonitorCacheEntryBlock *new_block;
         128                 :
         129           19965 :     entries = 1L << new_size_log2;
         130                 :
         131                 :     /*
         132                 :     ** Expand the monitor-cache-entry free list
         133                 :     */
         134           19965 :     new_block = (MonitorCacheEntryBlock*)
         135           19965 :         PR_CALLOC(sizeof(MonitorCacheEntryBlock)
         136                 :         + (entries - 1) * sizeof(MonitorCacheEntry));
         137           19965 :     if (NULL == new_block) return PR_FAILURE;
         138                 :
         139                 :     /*
         140                 :     ** Allocate system monitors for the new monitor cache entries. If we
         141                 :     ** run out of system monitors, break out of the loop.
         142                 :     */
         143          179685 :     for (i = 0, p = new_block->entries; i < entries; i++, p++) {
         144          159720 :         p->mon = PR_NewMonitor();
         145          159720 :         if (!p->mon)
         146               0 :             break;
         147                 :     }
         148           19965 :     added = i;
         149           19965 :     if (added != entries) {
         150                 :         MonitorCacheEntryBlock *realloc_block;
         151                 :
         152               0 :         if (added == 0) {
         153                 :             /* Totally out of system monitors. Lossage abounds */
         154               0 :             PR_DELETE(new_block);
         155               0 :             return PR_FAILURE;
         156                 :         }
         157                 :
         158                 :         /*
         159                 :         ** We were able to allocate some of the system monitors. Use
         160                 :         ** realloc to shrink down the new_block memory. If that fails,
         161                 :         ** carry on with the too-large new_block.
         162                 :         */
         163               0 :         realloc_block = (MonitorCacheEntryBlock*)
         164               0 :             PR_REALLOC(new_block, sizeof(MonitorCacheEntryBlock)
         165                 :             + (added - 1) * sizeof(MonitorCacheEntry));
         166               0 :         if (realloc_block)
         167               0 :             new_block = realloc_block;
         168                 :     }
         169                 :
         170                 :     /*
         171                 :     ** Now that we have allocated all of the system monitors, build up
         172                 :     ** the new free list. We can just update the free_list because we own
         173                 :     ** the mcache-lock and we aren't calling anyone who might want to use
         174                 :     ** it.
         175                 :     */
         176          159720 :     for (i = 0, p = new_block->entries; i < added - 1; i++, p++)
         177          139755 :         p->next = p + 1;
         178           19965 :     p->next = free_entries;
         179           19965 :     free_entries = new_block->entries;
         180           19965 :     num_free_entries += added;
         181           19965 :     new_block->next = mcache_blocks;
         182           19965 :     mcache_blocks = new_block;
         183                 :
         184                 :     /* Try to expand the hash table */
         185           19965 :     new_hash_buckets = (MonitorCacheEntry**)
         186           19965 :         PR_CALLOC(entries * sizeof(MonitorCacheEntry*));
         187           19965 :     if (NULL == new_hash_buckets) {
         188                 :         /*
         189                 :         ** Partial lossage. In this situation we don't get any more hash
         190                 :         ** buckets, which just means that the table lookups will take
         191                 :         ** longer. This is bad, but not fatal
         192                 :         */
         193               0 :         PR_LOG(_pr_cmon_lm, PR_LOG_WARNING,
         194                 :                ("unable to grow monitor cache hash buckets"));
         195               0 :         return PR_SUCCESS;
         196                 :     }
         197                 :
         198                 :     /*
         199                 :     ** Compute new hash mask value. This value is used to mask an address
         200                 :     ** until it's bits are in the right spot for indexing into the hash
         201                 :     ** table.
         202                 :     */
         203           19965 :     hash_mask = entries - 1;
         204                 :
         205                 :     /*
         206                 :     ** Expand the hash table. We have to rehash everything in the old
         207                 :     ** table into the new table.
         208                 :     */
         209           19965 :     old_hash_buckets = hash_buckets;
         210           19965 :     old_num_hash_buckets = num_hash_buckets;
         211           19965 :     for (i = 0; i < old_num_hash_buckets; i++) {
         212               0 :         p = old_hash_buckets[i];
         213               0 :         while (p) {
         214               0 :             MonitorCacheEntry *next = p->next;
         215                 :
         216                 :             /* Hash based on new table size, and then put p in the new table */
         217               0 :             PRUintn hash = HASH(p->address);
         218               0 :             p->next = new_hash_buckets[hash];
         219               0 :             new_hash_buckets[hash] = p;
         220                 :
         221               0 :             p = next;
         222                 :         }
         223                 :     }
         224                 :
         225                 :     /*
         226                 :     ** Switch over to new hash table and THEN call free of the old
         227                 :     ** table. Since free might re-enter _pr_mcache_lock, things would
         228                 :     ** break terribly if it used the old hash table.
         229                 :     */
         230           19965 :     hash_buckets = new_hash_buckets;
         231           19965 :     num_hash_buckets = entries;
         232           19965 :     num_hash_buckets_log2 = new_size_log2;
         233           19965 :     PR_DELETE(old_hash_buckets);
         234                 :
         235           19965 :     PR_LOG(_pr_cmon_lm, PR_LOG_NOTICE,
         236                 :            ("expanded monitor cache to %d (buckets %d)",
         237                 :             num_free_entries, entries));
         238                 :
         239           19965 :     return PR_SUCCESS;
         240                 : }  /* ExpandMonitorCache */
         241                 :
         242                 : /*
         243                 : ** Lookup a monitor cache entry by address. Return a pointer to the
         244                 : ** pointer to the monitor cache entry on success, null on failure.
         245                 : */
         246               0 : static MonitorCacheEntry **LookupMonitorCacheEntry(void *address)
         247                 : {
         248                 :     PRUintn hash;
         249                 :     MonitorCacheEntry **pp, *p;
         250                 :
         251               0 :     hash = HASH(address);
         252               0 :     pp = hash_buckets + hash;
         253               0 :     while ((p = *pp) != 0) {
         254               0 :         if (p->address == address) {
         255               0 :             if (p->cacheEntryCount > 0)
         256               0 :                 return pp;
         257               0 :             return NULL;
         258                 :         }
         259               0 :         pp = &p->next;
         260                 :     }
         261               0 :     return NULL;
         262                 : }
         263                 :
         264                 : /*
         265                 : ** Try to create a new cached monitor. If it's already in the cache,
         266                 : ** great - return it. Otherwise get a new free cache entry and set it
         267                 : ** up. If the cache free space is getting low, expand the cache.
         268                 : */
         269               0 : static PRMonitor *CreateMonitor(void *address)
         270                 : {
         271                 :     PRUintn hash;
         272                 :     MonitorCacheEntry **pp, *p;
         273                 :
         274               0 :     hash = HASH(address);
         275               0 :     pp = hash_buckets + hash;
         276               0 :     while ((p = *pp) != 0) {
         277               0 :         if (p->address == address) goto gotit;
         278                 :
         279               0 :         pp = &p->next;
         280                 :     }
         281                 :
         282                 :     /* Expand the monitor cache if we have run out of free slots in the table */
         283               0 :     if (num_free_entries < FREE_THRESHOLD) {
         284                 :         /* Expand monitor cache */
         285                 :
         286                 :         /*
         287                 :         ** This function is called with the lock held. So what's the 'expanding'
         288                 :         ** boolean all about? Seems a bit redundant.
         289                 :         */
         290               0 :         if (!expanding) {
         291                 :             PRStatus rv;
         292                 :
         293               0 :             expanding = PR_TRUE;
         294               0 :             rv = ExpandMonitorCache(num_hash_buckets_log2 + 1);
         295               0 :             expanding = PR_FALSE;
         296               0 :             if (PR_FAILURE == rv)  return NULL;
         297                 :
         298                 :             /* redo the hash because it'll be different now */
         299               0 :             hash = HASH(address);
         300                 :         } else {
         301                 :             /*
         302                 :             ** We are in process of expanding and we need a cache
         303                 :             ** monitor.  Make sure we have enough!
         304                 :             */
         305               0 :             PR_ASSERT(num_free_entries > 0);
         306                 :         }
         307                 :     }
         308                 :
         309                 :     /* Make a new monitor */
         310               0 :     p = free_entries;
         311               0 :     free_entries = p->next;
         312               0 :     num_free_entries--;
         313               0 :     if (OnMonitorRecycle && p->address)
         314               0 :         OnMonitorRecycle(p->address);
         315               0 :     p->address = address;
         316               0 :     p->next = hash_buckets[hash];
         317               0 :     hash_buckets[hash] = p;
         318               0 :     PR_ASSERT(p->cacheEntryCount == 0);
         319                 :
         320                 :   gotit:
         321               0 :     p->cacheEntryCount++;
         322               0 :     return p->mon;
         323                 : }
         324                 :
         325                 : /*
         326                 : ** Initialize the monitor cache
         327                 : */
         328           19965 : void _PR_InitCMon(void)
         329                 : {
         330           19965 :     _PR_NEW_LOCK_MCACHE();
         331           19965 :     ExpandMonitorCache(3);
         332           19965 : }
         333                 :
         334                 : /*
         335                 : ** Destroy the monitor cache
         336                 : */
         337             140 : void _PR_CleanupCMon(void)
         338                 : {
         339             140 :     _PR_DESTROY_LOCK_MCACHE();
         340                 :
         341            1400 :     while (free_entries) {
         342            1120 :         PR_DestroyMonitor(free_entries->mon);
         343            1120 :         free_entries = free_entries->next;
         344                 :     }
         345             140 :     num_free_entries = 0;
         346                 :
         347             420 :     while (mcache_blocks) {
         348                 :         MonitorCacheEntryBlock *block;
         349                 :
         350             140 :         block = mcache_blocks;
         351             140 :         mcache_blocks = block->next;
         352             140 :         PR_DELETE(block);
         353                 :     }
         354                 :
         355             140 :     PR_DELETE(hash_buckets);
         356             140 :     hash_mask = 0;
         357             140 :     num_hash_buckets = 0;
         358             140 :     num_hash_buckets_log2 = 0;
         359                 :
         360             140 :     expanding = PR_FALSE;
         361             140 :     OnMonitorRecycle = NULL;
         362             140 : }
         363                 :
         364                 : /*
         365                 : ** Create monitor for address. Don't enter the monitor while we have the
         366                 : ** mcache locked because we might block!
         367                 : */
         368               0 : PR_IMPLEMENT(PRMonitor*) PR_CEnterMonitor(void *address)
         369                 : {
         370                 :     PRMonitor *mon;
         371                 :
         372               0 :     if (!_pr_initialized) _PR_ImplicitInitialization();
         373                 :
         374               0 :     _PR_LOCK_MCACHE();
         375               0 :     mon = CreateMonitor(address);
         376               0 :     _PR_UNLOCK_MCACHE();
         377                 :
         378               0 :     if (!mon) return NULL;
         379                 :
         380               0 :     PR_EnterMonitor(mon);
         381               0 :     return mon;
         382                 : }
         383                 :
         384               0 : PR_IMPLEMENT(PRStatus) PR_CExitMonitor(void *address)
         385                 : {
         386                 :     MonitorCacheEntry **pp, *p;
         387               0 :     PRStatus status = PR_SUCCESS;
         388                 :
         389               0 :     _PR_LOCK_MCACHE();
         390               0 :     pp = LookupMonitorCacheEntry(address);
         391               0 :     if (pp != NULL) {
         392               0 :         p = *pp;
         393               0 :         if (--p->cacheEntryCount == 0) {
         394                 :             /*
         395                 :             ** Nobody is using the system monitor. Put it on the cached free
         396                 :             ** list. We are safe from somebody trying to use it because we
         397                 :             ** have the mcache locked.
         398                 :             */
         399               0 :             p->address = 0;             /* defensive move */
         400               0 :             *pp = p->next;              /* unlink from hash_buckets */
         401               0 :             p->next = free_entries;     /* link into free list */
         402               0 :             free_entries = p;
         403               0 :             num_free_entries++;         /* count it as free */
         404                 :         }
         405               0 :         status = PR_ExitMonitor(p->mon);
         406                 :     } else {
         407               0 :         status = PR_FAILURE;
         408                 :     }
         409               0 :     _PR_UNLOCK_MCACHE();
         410                 :
         411               0 :     return status;
         412                 : }
         413                 :
         414               0 : PR_IMPLEMENT(PRStatus) PR_CWait(void *address, PRIntervalTime ticks)
         415                 : {
         416                 :     MonitorCacheEntry **pp;
         417                 :     PRMonitor *mon;
         418                 :
         419               0 :     _PR_LOCK_MCACHE();
         420               0 :     pp = LookupMonitorCacheEntry(address);
         421               0 :     mon = pp ? ((*pp)->mon) : NULL;
         422               0 :     _PR_UNLOCK_MCACHE();
         423                 :
         424               0 :     if (mon == NULL)
         425               0 :         return PR_FAILURE;
         426               0 :     return PR_Wait(mon, ticks);
         427                 : }
         428                 :
         429               0 : PR_IMPLEMENT(PRStatus) PR_CNotify(void *address)
         430                 : {
         431                 :     MonitorCacheEntry **pp;
         432                 :     PRMonitor *mon;
         433                 :
         434               0 :     _PR_LOCK_MCACHE();
         435               0 :     pp = LookupMonitorCacheEntry(address);
         436               0 :     mon = pp ? ((*pp)->mon) : NULL;
         437               0 :     _PR_UNLOCK_MCACHE();
         438                 :
         439               0 :     if (mon == NULL)
         440               0 :         return PR_FAILURE;
         441               0 :     return PR_Notify(mon);
         442                 : }
         443                 :
         444               0 : PR_IMPLEMENT(PRStatus) PR_CNotifyAll(void *address)
         445                 : {
         446                 :     MonitorCacheEntry **pp;
         447                 :     PRMonitor *mon;
         448                 :
         449               0 :     _PR_LOCK_MCACHE();
         450               0 :     pp = LookupMonitorCacheEntry(address);
         451               0 :     mon = pp ? ((*pp)->mon) : NULL;
         452               0 :     _PR_UNLOCK_MCACHE();
         453                 :
         454               0 :     if (mon == NULL)
         455               0 :         return PR_FAILURE;
         456               0 :     return PR_NotifyAll(mon);
         457                 : }
         458                 :
         459                 : PR_IMPLEMENT(void)
         460               0 : PR_CSetOnMonitorRecycle(void (*callback)(void *address))
         461                 : {
         462               0 :     OnMonitorRecycle = callback;
         463               0 : }

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