Changeset 38859 in webkit for trunk/JavaScriptCore/wtf/HashTable.h

Timestamp:

Dec 1, 2008, 6:19:35 AM (16 years ago)

Author:

[email protected]

Message:

2008-12-01 David Levin <​[email protected]>

Reviewed by Alexey Proskuryakov.

​https://bugs.webkit.org/show_bug.cgi?id=22567
Make HashTable work as expected with respect to threads. Specifically, it has class-level
thread safety and constant methods work on constant objects without synchronization.

No observable change in behavior, so no test.

• wtf/HashTable.cpp: (WTF::hashTableStatsMutex): (WTF::HashTableStats::~HashTableStats): (WTF::HashTableStats::recordCollisionAtCount): Guarded variable access with a mutex.

• wtf/HashTable.h: (WTF::::lookup): (WTF::::lookupForWriting): (WTF::::fullLookupForWriting): (WTF::::add): (WTF::::reinsert): (WTF::::remove): (WTF::::rehash): Changed increments of static variables to use atomicIncrement.

(WTF::::invalidateIterators):
(WTF::addIterator):
(WTF::removeIterator):
Guarded mutable access with a mutex.

File:

• trunk/JavaScriptCore/wtf/HashTable.h (modified) (15 diffs)

trunk/JavaScriptCore/wtf/HashTable.h

@@ -1 +1 @@
 /*
  * Copyright (C) 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
+ * Copyright (C) 2008 David Levin <[email protected]>
  *
  * This library is free software; you can redistribute it and/or
@@ -25 +26 @@
 #include "HashTraits.h"
 #include <wtf/Assertions.h>
+#include <wtf/Threading.h>
 
 namespace WTF {
@@ -43 +45 @@
     struct HashTableStats {
         ~HashTableStats();
+        // All of the variables are accessed in ~HashTableStats when the static struct is destroyed.
+
+        // The following variables are all atomically incremented when modified.
         static int numAccesses;
-        static int numCollisions;
-        static int collisionGraph[4096];
-        static int maxCollisions;
         static int numRehashes;
         static int numRemoves;
         static int numReinserts;
+
+        // The following variables are only modified in the recordCollisionAtCount method within a mutex.
+        static int maxCollisions;
+        static int numCollisions;
+        static int collisionGraph[4096];
+
         static void recordCollisionAtCount(int count);
     };
@@ -202 +210 @@
 #if CHECK_HASHTABLE_ITERATORS
     public:
+        // Any modifications of the m_next or m_previous of an iterator that is in a linked list of a HashTable::m_iterator,
+        // should be guarded with m_table->m_mutex.
         mutable const HashTableType* m_table;
         mutable const_iterator* m_next;
@@ -398 +408 @@
 #if CHECK_HASHTABLE_ITERATORS
     public:
+        // All access to m_iterators should be guarded with m_mutex.
         mutable const_iterator* m_iterators;
+        mutable Mutex m_mutex;
 #endif
     };
@@ -467 +479 @@
 
 #if DUMP_HASHTABLE_STATS
-        ++HashTableStats::numAccesses;
+        atomicIncrement(&HashTableStats::numAccesses);
         int probeCount = 0;
 #endif
@@ -512 +524 @@
 
 #if DUMP_HASHTABLE_STATS
-        ++HashTableStats::numAccesses;
+        atomicIncrement(&HashTableStats::numAccesses);
         int probeCount = 0;
 #endif
@@ -564 +576 @@
 
 #if DUMP_HASHTABLE_STATS
-        ++HashTableStats::numAccesses;
+        atomicIncrement(&HashTableStats::numAccesses);
         int probeCount = 0;
 #endif
@@ -624 +636 @@
 
 #if DUMP_HASHTABLE_STATS
-        ++HashTableStats::numAccesses;
+        atomicIncrement(&HashTableStats::numAccesses);
         int probeCount = 0;
 #endif
@@ -739 +751 @@
         ASSERT(!isDeletedBucket(*(lookupForWriting(Extractor::extract(entry)).first)));
 #if DUMP_HASHTABLE_STATS
-        ++HashTableStats::numReinserts;
+        atomicIncrement(&HashTableStats::numReinserts);
 #endif
 
@@ -802 +814 @@
     {
 #if DUMP_HASHTABLE_STATS
-        ++HashTableStats::numRemoves;
+        atomicIncrement(&HashTableStats::numRemoves);
 #endif
 
@@ -888 +900 @@
 #if DUMP_HASHTABLE_STATS
         if (oldTableSize != 0)
-            ++HashTableStats::numRehashes;
+            atomicIncrement(&HashTableStats::numRehashes);
 #endif
 
@@ -1017 +1029 @@
     void HashTable<Key, Value, Extractor, HashFunctions, Traits, KeyTraits>::invalidateIterators()
     {
+        MutexLocker lock(m_mutex);
         const_iterator* next;
         for (const_iterator* p = m_iterators; p; p = next) {
@@ -1038 +1051 @@
             it->m_next = 0;
         } else {
+            MutexLocker lock(table->m_mutex);
             ASSERT(table->m_iterators != it);
             it->m_next = table->m_iterators;
@@ -1059 +1073 @@
             ASSERT(!it->m_previous);
         } else {
+            MutexLocker lock(it->m_table->m_mutex);
             if (it->m_next) {
                 ASSERT(it->m_next->m_previous == it);