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: 2012-06-02 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           20034 : 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           20034 :     entries = 1L << new_size_log2;
     130                 : 
     131                 :     /*
     132                 :     ** Expand the monitor-cache-entry free list
     133                 :     */
     134           20034 :     new_block = (MonitorCacheEntryBlock*)
     135           20034 :         PR_CALLOC(sizeof(MonitorCacheEntryBlock)
     136                 :         + (entries - 1) * sizeof(MonitorCacheEntry));
     137           20034 :     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          180306 :     for (i = 0, p = new_block->entries; i < entries; i++, p++) {
     144          160272 :         p->mon = PR_NewMonitor();
     145          160272 :         if (!p->mon)
     146               0 :             break;
     147                 :     }
     148           20034 :     added = i;
     149           20034 :     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          160272 :     for (i = 0, p = new_block->entries; i < added - 1; i++, p++)
     177          140238 :         p->next = p + 1;
     178           20034 :     p->next = free_entries;
     179           20034 :     free_entries = new_block->entries;
     180           20034 :     num_free_entries += added;
     181           20034 :     new_block->next = mcache_blocks;
     182           20034 :     mcache_blocks = new_block;
     183                 : 
     184                 :     /* Try to expand the hash table */
     185           20034 :     new_hash_buckets = (MonitorCacheEntry**)
     186           20034 :         PR_CALLOC(entries * sizeof(MonitorCacheEntry*));
     187           20034 :     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           20034 :     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           20034 :     old_hash_buckets = hash_buckets;
     210           20034 :     old_num_hash_buckets = num_hash_buckets;
     211           20034 :     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           20034 :     hash_buckets = new_hash_buckets;
     231           20034 :     num_hash_buckets = entries;
     232           20034 :     num_hash_buckets_log2 = new_size_log2;
     233           20034 :     PR_DELETE(old_hash_buckets);
     234                 : 
     235           20034 :     PR_LOG(_pr_cmon_lm, PR_LOG_NOTICE,
     236                 :            ("expanded monitor cache to %d (buckets %d)",
     237                 :             num_free_entries, entries));
     238                 : 
     239           20034 :     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           20034 : void _PR_InitCMon(void)
     329                 : {
     330           20034 :     _PR_NEW_LOCK_MCACHE();
     331           20034 :     ExpandMonitorCache(3);
     332           20034 : }
     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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