The hash table implementation had some static free lists that were

not protected by locks in the threaded RTS.  This moves the free lists
to the individual hash tables and removes the static variables.

Spotted by Marcin Orczyk <orczykm@dcs.gla.ac.uk>, thanks!  This could
definitely cause actual crashes.

1 files changed, 33 insertions, 34 deletions

diff --git a/rts/Hash.c b/rts/Hash.c
index 09d0a06808..9c9b2bce42 100644
--- a/rts/Hash.c
+++ b/rts/Hash.c
@@ -27,13 +27,16 @@
 
 
 /* Linked list of (key, data) pairs for separate chaining */
-struct hashlist {
+typedef struct hashlist {
     StgWord key;
     void *data;
     struct hashlist *next;  /* Next cell in bucket chain (same hash value) */
-};
+} HashList;
 
-typedef struct hashlist HashList;
+typedef struct chunklist {
+  HashList *chunk;
+  struct chunklist *next;
+} HashListChunk;
 
 struct hashtable {
     int split;		    /* Next bucket to split when expanding */
@@ -43,7 +46,9 @@ struct hashtable {
     int kcount;		    /* Number of keys */
     int bcount;		    /* Number of buckets */
     HashList **dir[HDIRSIZE];	/* Directory of segments */
-    HashFunction *hash;		/* hash function */
+    HashList *freeList;         /* free list of HashLists */
+    HashListChunk *chunks;
+    HashFunction *hash;         /* hash function */
     CompareFunction *compare;   /* key comparison function */
 };
 
@@ -207,30 +212,23 @@ lookupHashTable(HashTable *table, StgWord key)
  * no effort to actually return the space to the malloc arena.
  * -------------------------------------------------------------------------- */
 
-static HashList *freeList = NULL;
-
-static struct chunkList {
-  void *chunk;
-  struct chunkList *next;
-} *chunks;
-
 static HashList *
-allocHashList(void)
+allocHashList (HashTable *table)
 {
     HashList *hl, *p;
-    struct chunkList *cl;
+    HashListChunk *cl;
 
-    if ((hl = freeList) != NULL) {
-	freeList = hl->next;
+    if ((hl = table->freeList) != NULL) {
+        table->freeList = hl->next;
     } else {
         hl = stgMallocBytes(HCHUNK * sizeof(HashList), "allocHashList");
 	cl = stgMallocBytes(sizeof (*cl), "allocHashList: chunkList");
-	cl->chunk = hl;
-	cl->next = chunks;
-	chunks = cl;
+        cl->chunk = hl;
+        cl->next = table->chunks;
+        table->chunks = cl;
 
-	freeList = hl + 1;
-	for (p = freeList; p < hl + HCHUNK - 1; p++)
+        table->freeList = hl + 1;
+        for (p = table->freeList; p < hl + HCHUNK - 1; p++)
 	    p->next = p + 1;
 	p->next = NULL;
     }
@@ -238,10 +236,10 @@ allocHashList(void)
 }
 
 static void
-freeHashList(HashList *hl)
+freeHashList (HashTable *table, HashList *hl)
 {
-    hl->next = freeList;
-    freeList = hl;
+    hl->next = table->freeList;
+    table->freeList = hl;
 }
 
 void
@@ -264,7 +262,7 @@ insertHashTable(HashTable *table, StgWord key, void *data)
     segment = bucket / HSEGSIZE;
     index = bucket % HSEGSIZE;
 
-    hl = allocHashList();
+    hl = allocHashList(table);
 
     hl->key = key;
     hl->data = data;
@@ -292,7 +290,7 @@ removeHashTable(HashTable *table, StgWord key, void *data)
 		table->dir[segment][index] = hl->next;
 	    else
 		prev->next = hl->next;
-	    freeHashList(hl);
+            freeHashList(table,hl);
 	    table->kcount--;
 	    return hl->data;
 	}
@@ -317,6 +315,7 @@ freeHashTable(HashTable *table, void (*freeDataFun)(void *) )
     long index;
     HashList *hl;
     HashList *next;
+    HashListChunk *cl, *cl_next;
 
     /* The last bucket with something in it is table->max + table->split - 1 */
     segment = (table->max + table->split - 1) / HSEGSIZE;
@@ -328,14 +327,18 @@ freeHashTable(HashTable *table, void (*freeDataFun)(void *) )
 		next = hl->next;
 		if (freeDataFun != NULL)
 		    (*freeDataFun)(hl->data);
-		freeHashList(hl);
-	    }
+            }
 	    index--;
 	}
 	stgFree(table->dir[segment]);
 	segment--;
 	index = HSEGSIZE - 1;
     }
+    for (cl = table->chunks; cl != NULL; cl = cl_next) {
+        cl_next = cl->next;
+        stgFree(cl->chunk);
+        stgFree(cl);
+    }
     stgFree(table);
 }
 
@@ -363,6 +366,8 @@ allocHashTable_(HashFunction *hash, CompareFunction *compare)
     table->mask2 = 2 * HSEGSIZE - 1;
     table->kcount = 0;
     table->bcount = HSEGSIZE;
+    table->freeList = NULL;
+    table->chunks = NULL;
     table->hash = hash;
     table->compare = compare;
 
@@ -385,11 +390,5 @@ allocStrHashTable(void)
 void
 exitHashTable(void)
 {
-  struct chunkList *cl;
-
-  while ((cl = chunks) != NULL) {
-    chunks = cl->next;
-    stgFree(cl->chunk);
-    stgFree(cl);
-  }
+    /* nothing to do */
 }