service_runtime/nacl_sync_queue.c

   1 /*
   2  * Copyright 2008, Google Inc.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met:
   8  *
   9  *     * Redistributions of source code must retain the above copyright
  10  * notice, this list of conditions and the following disclaimer.
  11  *     * Redistributions in binary form must reproduce the above
  12  * copyright notice, this list of conditions and the following disclaimer
  13  * in the documentation and/or other materials provided with the
  14  * distribution.
  15  *     * Neither the name of Google Inc. nor the names of its
  16  * contributors may be used to endorse or promote products derived from
  17  * this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  23  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * NaCl service runtime synchronized queue.
  34  */
  35
  36 #include "native_client/service_runtime/nacl_sync_queue.h"
  37
  38 #include "native_client/service_runtime/nacl_check.h"
  39 #include "native_client/service_runtime/nacl_log.h"
  40 #include "native_client/service_runtime/nacl_sync_checked.h"
  41
  42 struct NaClSyncQueueItem {
  43   struct NaClSyncQueueItem  *next;
  44   void                      *item;  /* arbitrary object */
  45 };
  46
  47 int NaClSyncQueueEmptyMu(struct NaClSyncQueue *nsqp)
  48 {
  49   return NULL == nsqp->head;
  50 }
  51
  52 int NaClSyncQueueEmpty(struct NaClSyncQueue *nsqp)
  53 {
  54   int empty;
  55
  56   NaClXMutexLock(&nsqp->mu);
  57   empty = NaClSyncQueueEmptyMu(nsqp);
  58   NaClXMutexUnlock(&nsqp->mu);
  59   return empty;
  60 }
  61
  62 int NaClSyncQueueCtor(struct NaClSyncQueue *nsqp)
  63 {
  64   if (!NaClMutexCtor(&nsqp->mu)) {
  65     return 0;
  66   }
  67   if (!NaClCondVarCtor(&nsqp->cv)) {
  68     NaClMutexDtor(&nsqp->mu);
  69     return 0;
  70   }
  71   nsqp->head = NULL;
  72   nsqp->insert_pt = &nsqp->head;
  73   nsqp->quit = 0;
  74
  75   /* post-condition: NaClSyncQueueEmpty(nsqp) != 0 */
  76   return 1;
  77 }
  78
  79 void NaClSyncQueueDtor(struct NaClSyncQueue *nsqp)
  80 {
  81   /*
  82    * NB: sanity check is not complete, since after dropping the lock
  83    * and prior to deallocating the mutex, another (confused) thread
  84    * could come along and insert an object.  Since such a confused
  85    * thread might try to insert an object into the queue even after
  86    * the mutex and condvar is dtor'd, we're pretty much stuck.
  87    */
  88   CHECK(NaClSyncQueueEmpty(nsqp));
  89   NaClMutexDtor(&nsqp->mu);
  90   NaClCondVarDtor(&nsqp->cv);
  91 }
  92
  93 void NaClSyncQueueInsert(struct NaClSyncQueue *nsqp,
  94                          void                 *item)
  95 {
  96   struct NaClSyncQueueItem  *nsqip;
  97
  98   NaClLog(3, "NaClSyncQueueInsert(0x%08"PRIxPTR",0x%08"PRIxPTR")\n",
  99           (uintptr_t) nsqp,
 100           (uintptr_t) item);
 101
 102   nsqip = malloc(sizeof *nsqip);
 103   if (NULL == nsqip) {
 104     NaClLog(LOG_FATAL, "Out of memory for NaClSyncQueue item\n");
 105   }
 106   nsqip->next = NULL;
 107   nsqip->item = item;
 108   NaClXMutexLock(&nsqp->mu);
 109   *nsqp->insert_pt = nsqip;
 110   nsqp->insert_pt = &nsqip->next;
 111   NaClXCondVarSignal(&nsqp->cv);  /* non-empty or quit*/
 112   NaClXMutexUnlock(&nsqp->mu);
 113
 114 }
 115
 116 void NaClSyncQueueQuit(struct NaClSyncQueue *nsqp)
 117 {
 118   NaClXMutexLock(&nsqp->mu);
 119   nsqp->quit = 1;
 120   NaClXCondVarSignal(&nsqp->cv);
 121   NaClXMutexUnlock(&nsqp->mu);
 122 }
 123
 124 void *NaClSyncQueueDequeue(struct NaClSyncQueue *nsqp)
 125 {
 126   struct NaClSyncQueueItem  *qitem;
 127   void                      *item;
 128
 129   NaClLog(3, "NaClSyncQueueDequeue: waiting on queue 0x%08"PRIxPTR"\n",
 130           (uintptr_t) nsqp);
 131   NaClXMutexLock(&nsqp->mu);
 132   while (NaClSyncQueueEmptyMu(nsqp) && !nsqp->quit) {
 133     NaClLog(3, "NaClSyncQueueDequeue: waiting\n");
 134     NaClCondVarWait(&nsqp->cv, &nsqp->mu);
 135   }
 136
 137   if (nsqp->quit) {
 138     item = NULL;
 139   } else {
 140     CHECK(!NaClSyncQueueEmptyMu(nsqp));
 141
 142     qitem = nsqp->head;
 143     nsqp->head = qitem->next;
 144     if (NULL == nsqp->head) {
 145       nsqp->insert_pt = &nsqp->head;
 146     }
 147     item = qitem->item;
 148     free(qitem);
 149   }
 150
 151   NaClXMutexUnlock(&nsqp->mu);
 152
 153   NaClLog(3, "NaClSyncQueueDequeue: returning item 0x%08"PRIxPTR"\n",
 154           (uintptr_t) item);
 155   return item;
 156 }