Changeset 38dc82d in mainline for kernel/generic/src/mm/page.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/generic/src/mm/page.c (modified) (3 diffs)

kernel/generic/src/mm/page.c

@@ -137 +137 @@
 /** Find mapping for virtual page.
  *
- * @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.
- *
- */
-NO_TRACE pte_t *page_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.
+ */
+NO_TRACE bool page_mapping_find(as_t *as, uintptr_t page, bool nolock,
+    pte_t *pte)
 {
         ASSERT(nolock || page_table_locked(as));
@@ -153 +153 @@
         
         return page_mapping_operations->mapping_find(as,
-            ALIGN_DOWN(page, PAGE_SIZE), nolock);
+            ALIGN_DOWN(page, PAGE_SIZE), nolock, pte);
 }
 
@@ -173 +173 @@
         page_table_lock(AS, true);
         
-        pte_t *pte = page_mapping_find(AS, virt, false);
-        if ((!PTE_VALID(pte)) || (!PTE_PRESENT(pte))) {
+        pte_t pte;
+        bool found = page_mapping_find(AS, virt, false, &pte);
+        if (!found || !PTE_VALID(&pte) || !PTE_PRESENT(&pte)) {
                 page_table_unlock(AS, true);
                 return ENOENT;
         }
         
-        *phys = PTE_GET_FRAME(pte) +
+        *phys = PTE_GET_FRAME(&pte) +
             (virt - ALIGN_DOWN(virt, PAGE_SIZE));