Changeset 7e4e532 in mainline for generic/src/mm/as.c

Timestamp:

2006-02-08T23:37:38Z (19 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

874878a

Parents:

bb68433

Message:

Reimplement ASID stealing logic.
This time, hopefully, with correct synchronization.

File:

• generic/src/mm/as.c (modified) (4 diffs)

generic/src/mm/as.c

@@ -57 +57 @@
 as_operations_t *as_operations = NULL;
 
+/** Address space lock. It protects inactive_as_with_asid_head. */
+SPINLOCK_INITIALIZE(as_lock);
+
+/**
+ * This list contains address spaces that are not active on any
+ * processor and that have valid ASID.
+ */
+LIST_INITIALIZE(inactive_as_with_asid_head);
+
 /** Kernel address space. */
 as_t *AS_KERNEL = NULL;
@@ -80 +89 @@
 
         as = (as_t *) malloc(sizeof(as_t), 0);
-
-        list_initialize(&as->as_with_asid_link);
+        link_initialize(&as->inactive_as_with_asid_link);
         spinlock_initialize(&as->lock, "as_lock");
         list_initialize(&as->as_area_head);
@@ -90 +98 @@
                 as->asid = ASID_INVALID;
         
+        as->refcount = 0;
         as->page_table = page_table_create(flags);
 
@@ -268 +277 @@
 }
 
-/** Install address space on CPU.
- *
- * @param as Address space.
- */
-void as_install(as_t *as)
+/** Switch address spaces.
+ *
+ * @param old Old address space or NULL.
+ * @param new New address space.
+ */
+void as_switch(as_t *old, as_t *new)
 {
         ipl_t ipl;
-        
-        asid_install(as);
+        bool needs_asid = false;
         
         ipl = interrupts_disable();
-        spinlock_lock(&as->lock);
-        SET_PTL0_ADDRESS(as->page_table);
-        spinlock_unlock(&as->lock);
+        spinlock_lock(&as_lock);
+
+        /*
+         * First, take care of the old address space.
+         */     
+        if (old) {
+                spinlock_lock(&old->lock);
+                ASSERT(old->refcount);
+                if((--old->refcount == 0) && (old != AS_KERNEL)) {
+                        /*
+                         * The old address space is no longer active on
+                         * any processor. It can be appended to the
+                         * list of inactive address spaces with assigned
+                         * ASID.
+                         */
+                         ASSERT(old->asid != ASID_INVALID);
+                         list_append(&old->inactive_as_with_asid_link, &inactive_as_with_asid_head);
+                }
+                spinlock_unlock(&old->lock);
+        }
+
+        /*
+         * Second, prepare the new address space.
+         */
+        spinlock_lock(&new->lock);
+        if ((new->refcount++ == 0) && (new != AS_KERNEL)) {
+                if (new->asid != ASID_INVALID)
+                        list_remove(&new->inactive_as_with_asid_link);
+                else
+                        needs_asid = true;      /* defer call to asid_get() until new->lock is released */
+        }
+        SET_PTL0_ADDRESS(new->page_table);
+        spinlock_unlock(&new->lock);
+
+        if (needs_asid) {
+                /*
+                 * Allocation of new ASID was deferred
+                 * until now in order to avoid deadlock.
+                 */
+                asid_t asid;
+                
+                asid = asid_get();
+                spinlock_lock(&new->lock);
+                new->asid = asid;
+                spinlock_unlock(&new->lock);
+        }
+        spinlock_unlock(&as_lock);
         interrupts_restore(ipl);
-
+        
         /*
          * Perform architecture-specific steps.
          * (e.g. write ASID to hardware register etc.)
          */
-        as_install_arch(as);
-        
-        AS = as;
+        as_install_arch(new);
+        
+        AS = new;
 }