Changeset d9e9caf in mainline

Timestamp:

2008-04-15T02:45:48Z (16 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

80e8482

Parents:

e13d1feb

Message:

Add a locking scheme for FAT in-core cache and nodes.

Location:

uspace/srv/fs/fat

Files:

• fat.h (modified) (1 diff)
• fat_ops.c (modified) (8 diffs)

uspace/srv/fs/fat/fat.h

@@ -148 +148 @@
 /** FAT in-core node. */
 typedef struct {
+        /** Protects an instance of this type. */
+        futex_t                 lock;
         fat_node_type_t         type;
         /** VFS index is the node's first allocated cluster. */

uspace/srv/fs/fat/fat_ops.c

@@ -47 +47 @@
 #include <libadt/list.h>
 #include <assert.h>
+#include <futex.h>
 
 #define BS_BLOCK                0
@@ -52 +53 @@
 #define FIN_KEY_DEV_HANDLE      0
 #define FIN_KEY_INDEX           1
+
+/** Futex protecting both fin_hash and ffn_head. */
+futex_t fin_futex = FUTEX_INITIALIZER;
 
 /** Hash table of FAT in-core nodes. */
@@ -119 +123 @@
 static void fat_node_initialize(fat_node_t *node)
 {
+        futex_initialize(&node->lock, 1);
         node->type = 0;
         node->index = 0;
@@ -201 +206 @@
         };
 
+        futex_down(&fin_futex);
         lnk = hash_table_find(&fin_hash, key);
         if (lnk) {
@@ -209 +215 @@
                 if (!node->refcnt++)
                         list_remove(&node->ffn_link);
+                futex_up(&fin_futex);
+                
+                /* Make sure that the node is fully instantiated. */
+                futex_down(&node->lock);
+                futex_up(&node->lock);
+                
                 return (void *) node;   
         }
@@ -242 +254 @@
         node->index = index;
         node->pindex = pindex;
+        key[FIN_KEY_DEV_HANDLE] = node->dev_handle;
+        key[FIN_KEY_INDEX] = node->index;
+        hash_table_insert(&fin_hash, key, &node->fin_link);
+
+        /*
+         * We have already put the node back to fin_hash.
+         * The node is not yet fully instantiated so we lock it prior to
+         * unlocking fin_hash.
+         */
+        futex_down(&node->lock);
+        futex_up(&fin_futex);
 
         /*
@@ -269 +292 @@
         node->size = uint32_t_le2host(d->size);
         block_put(b);
-        
-        key[FIN_KEY_DEV_HANDLE] = node->dev_handle;
-        key[FIN_KEY_INDEX] = node->index;
-        hash_table_insert(&fin_hash, key, &node->fin_link);
-
+
+        futex_up(&node->lock);
         return node;
 }
@@ -281 +301 @@
         fat_node_t *nodep = (fat_node_t *)node;
 
-        if (nodep->refcnt-- == 1)
+        futex_down(&fin_futex);
+        if (!--nodep->refcnt)
                 list_append(&nodep->ffn_link, &ffn_head);
+        futex_up(&fin_futex);
 }