Changeset 78a1b7b in mainline for uspace/srv/fs/fat/fat_idx.c

Timestamp:

2008-05-16T21:31:31Z (17 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

add5835

Parents:

4452366

Message:

Introduce a futex protecting the up_hash and ui_hash.

File:

• uspace/srv/fs/fat/fat_idx.c (modified) (4 diffs)

uspace/srv/fs/fat/fat_idx.c

@@ -74 +74 @@
 /** List of unused structures. */
 static LIST_INITIALIZE(unused_head);
+
+/** Futex protecting the up_hash and ui_hash.
+ *
+ * The locking strategy assumes that there will be at most one fibril for each
+ * dev_handle.  Therefore it will be sufficient to hold the futex for shorter
+ * times (i.e. only during hash table operations as opposed to holding it the
+ * whole time between an unsuccessful find and the following insert). Should the
+ * assumption break, the locking strategy for this futex will have to be
+ * reconsidered.
+ */
+static futex_t used_futex = FUTEX_INITIALIZER; 
 
 /**
@@ -340 +351 @@
         };
 
+        futex_down(&used_futex);
         l = hash_table_find(&up_hash, pkey);
+        futex_up(&used_futex);
         if (l) {
                 fidx = hash_table_get_instance(l, fat_idx_t, uph_link);
@@ -365 +378 @@
                 fidx->nodep = NULL;
 
+                futex_down(&used_futex);
                 hash_table_insert(&up_hash, pkey, &fidx->uph_link);
                 hash_table_insert(&ui_hash, ikey, &fidx->uih_link);
+                futex_up(&used_futex);
         }
 
@@ -382 +397 @@
         };
 
+        futex_down(&used_futex);
         l = hash_table_find(&ui_hash, ikey);
+        futex_up(&used_futex);
         if (l) {
                 fidx = hash_table_get_instance(l, fat_idx_t, uih_link);