Changeset 38dc82d in mainline for kernel/genarch/src/mm/page_ht.c

Timestamp:

2016-08-31T14:16:45Z (9 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

346b12a2

Parents:

dc05a9a

Message:

Make page_mapping_find() return a copy rather than the actual PTE

This makes page_mapping_find() more suitable for use with lock-free data
structures such as CHT that guarantee existence of the data only for
some limited time while a condition holds (e.g. inside of a RCU-protected
critical section that must be around all CHT lookups).

File:

• kernel/genarch/src/mm/page_ht.c (modified) (3 diffs)

kernel/genarch/src/mm/page_ht.c

@@ -59 +59 @@
 static void ht_mapping_insert(as_t *, uintptr_t, uintptr_t, unsigned int);
 static void ht_mapping_remove(as_t *, uintptr_t);
-static pte_t *ht_mapping_find(as_t *, uintptr_t, bool);
+static bool ht_mapping_find(as_t *, uintptr_t, bool, pte_t *);
 static void ht_mapping_make_global(uintptr_t, size_t);
 
@@ -248 +248 @@
 /** Find mapping for virtual page in page hash table.
  *
- * @param as     Address space to which page belongs.
- * @param page   Virtual page.
- * @param nolock True if the page tables need not be locked.
- *
- * @return NULL if there is no such mapping; requested mapping otherwise.
- *
- */
-pte_t *ht_mapping_find(as_t *as, uintptr_t page, bool nolock)
+ * @param as       Address space to which page belongs.
+ * @param page     Virtual page.
+ * @param nolock   True if the page tables need not be locked.
+ * @param[out] pte Structure that will receive a copy of the found PTE.
+ *
+ * @return True if the mapping was found, false otherwise.
+ */
+bool ht_mapping_find(as_t *as, uintptr_t page, bool nolock, pte_t *pte)
 {
         sysarg_t key[2] = {
@@ -266 +266 @@
         link_t *cur = hash_table_find(&page_ht, key);
         if (cur)
-                return hash_table_get_instance(cur, pte_t, link);
-        
-        return NULL;
+                *pte = *hash_table_get_instance(cur, pte_t, link);
+        
+        return cur != NULL;
 }