WebSVN – HelenOS – Diff – /trunk/kernel/generic/src/mm/as.c

  */
 static slab_cache_t *as_slab;
 #endif
 /**
+ * This lock serializes access to the ASID subsystem.
+ * It protects:
- * This lock protects inactive_as_with_asid_head list. It must be acquired
+ * - inactive_as_with_asid_head list
+ * - as->asid for each as of the as_t type
- * before as_t mutex.
+ * - asids_allocated counter
  */
-SPINLOCK_INITIALIZE(inactive_as_with_asid_lock);
+SPINLOCK_INITIALIZE(asidlock);
 /**
  * This list contains address spaces that are not active on any
  * processor and that have valid ASID.
  */
     /*
      * Since there is no reference to this area,
      * it is safe not to lock its mutex.
      */
     ipl = interrupts_disable();
-    spinlock_lock(&inactive_as_with_asid_lock);
+    spinlock_lock(&asidlock);
     if (as->asid != ASID_INVALID && as != AS_KERNEL) {
         if (as != AS && as->cpu_refcount == 0)
             list_remove(&as->inactive_as_with_asid_link);
         asid_put(as->asid);
+    }
-    spinlock_unlock(&inactive_as_with_asid_lock);
+    spinlock_unlock(&asidlock);
     /*
      * Destroy address space areas of the address space.
      * The B+tree must be walked carefully because it is
      * also being destroyed.
+}
 /** Switch address spaces.
+ *
  * Note that this function cannot sleep as it is essentially a part of
- * scheduling. Sleeping here would lead to deadlock on wakeup.
+ * scheduling. Sleeping here would lead to deadlock on wakeup. Another
+ * thing which is forbidden in this context is locking the address space.
+ *
  * @param old Old address space or NULL.
  * @param new New address space.
  */
 void as_switch(as_t *old_as, as_t *new_as)
+{
-    ipl_t ipl;
-    bool needs_asid = false;
-    ipl = interrupts_disable();
-    spinlock_lock(&inactive_as_with_asid_lock);
+    spinlock_lock(&asidlock);
     /*
      * First, take care of the old address space.
      */
     if (old_as) {
-        mutex_lock_active(&old_as->lock);
         ASSERT(old_as->cpu_refcount);
         if((--old_as->cpu_refcount == 0) && (old_as != AS_KERNEL)) {
             /*
              * The old address space is no longer active on
              * any processor. It can be appended to the
              */
             ASSERT(old_as->asid != ASID_INVALID);
             list_append(&old_as->inactive_as_with_asid_link,
                 &inactive_as_with_asid_head);
+        }
-        mutex_unlock(&old_as->lock);
         /*
          * Perform architecture-specific tasks when the address space
          * is being removed from the CPU.
          */
+    }
     /*
      * Second, prepare the new address space.
      */
-    mutex_lock_active(&new_as->lock);
     if ((new_as->cpu_refcount++ == 0) && (new_as != AS_KERNEL)) {
-        if (new_as->asid != ASID_INVALID) {
+        if (new_as->asid != ASID_INVALID)
             list_remove(&new_as->inactive_as_with_asid_link);
-        } else {
+        else
-            /*
-             * Defer call to asid_get() until new_as->lock is released.
-             */
-            needs_asid = true;
+            new_as->asid = asid_get();
-        }
+    }
 #ifdef AS_PAGE_TABLE
     SET_PTL0_ADDRESS(new_as->genarch.page_table);
 #endif
-    mutex_unlock(&new_as->lock);
-    if (needs_asid) {
-        /*
-         * Allocation of new ASID was deferred
-         * until now in order to avoid deadlock.
-         */
-        asid_t asid;
-        asid = asid_get();
-        mutex_lock_active(&new_as->lock);
-        new_as->asid = asid;
-        mutex_unlock(&new_as->lock);
-    }
-    spinlock_unlock(&inactive_as_with_asid_lock);
-    interrupts_restore(ipl);
     /*
      * Perform architecture-specific steps.
      * (e.g. write ASID to hardware register etc.)
      */
     as_install_arch(new_as);
+    spinlock_unlock(&asidlock);
     AS = new_as;
+}
 /** Convert address space area flags to page flags.

Subversion Repositories HelenOS

(root)/trunk/kernel/generic/src/mm/as.c – Rev 2141 → 2170