Changeset 38dc82d in mainline for kernel/generic/src/synch/futex.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/synch/futex.c (modified) (2 diffs)

kernel/generic/src/synch/futex.c

@@ -291 +291 @@
         spinlock_lock(&futex_ht_lock);
 
-        bool found = false;
-        pte_t *t = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE), true);
-        
-        if (t && PTE_VALID(t) && PTE_PRESENT(t)) {
-                found = true;
-                *paddr = PTE_GET_FRAME(t) + (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
+        bool success = false;
+
+        pte_t t;
+        bool found;
+
+        found = page_mapping_find(AS, ALIGN_DOWN(uaddr, PAGE_SIZE), true, &t);
+        if (found && PTE_VALID(&t) && PTE_PRESENT(&t)) {
+                success = true;
+                *paddr = PTE_GET_FRAME(&t) +
+                    (uaddr - ALIGN_DOWN(uaddr, PAGE_SIZE));
         }
         
@@ -302 +306 @@
         page_table_unlock(AS, false);
         
-        return found;
+        return success;
 }