WebSVN – HelenOS-historic – Diff – /kernel/trunk/genarch/src/mm/asid.c

 /*
  * Copyright (C) 2006 Jakub Jermar
  * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
+ *
  * - Redistributions of source code must retain the above copyright
  *   notice, this list of conditions and the following disclaimer.
  * - Redistributions in binary form must reproduce the above copyright
  *   notice, this list of conditions and the following disclaimer in the
  *   documentation and/or other materials provided with the distribution.
  * - The name of the author may not be used to endorse or promote products
  *   derived from this software without specific prior written permission.
+ *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 /*
  * ASID management.
+ *
  * Modern processor architectures optimize TLB utilization
  * by using ASIDs (a.k.a. memory contexts on sparc64 and
  * region identifiers on ia64). These ASIDs help to associate
  * each TLB item with an address space, thus making
  * finer-grained TLB invalidation possible.
+ *
  * Unfortunatelly, there are usually less ASIDs available than
  * there can be unique as_t structures (i.e. address spaces
  * recognized by the kernel).
+ *
  * When system runs short of ASIDs, it will attempt to steal
  * ASID from an address space that has not been active for
  * a while.
+ *
+ * This code depends on the fact that ASIDS_ALLOCABLE
+ * is greater than number of supported CPUs (i.e. the
+ * amount of concurently active address spaces).
+ *
  * Architectures that don't have hardware support for address
  * spaces do not compile with this file.
  */
 #include <mm/asid.h>
 #include <mm/as.h>
 #include <mm/tlb.h>
 #include <arch/mm/asid.h>
 #include <synch/spinlock.h>
 #include <arch.h>
 #include <adt/list.h>
 #include <debug.h>
 /**
- * asidlock protects both the asids_allocated counter
+ * asidlock protects the asids_allocated counter.
- * and the list of address spaces that were already
- * assigned ASID.
  */
 SPINLOCK_INITIALIZE(asidlock);
 static count_t asids_allocated = 0;
-/**
- * List of address spaces with assigned ASID.
- * When the system runs short of allocable
- * ASIDS, inactive address spaces are guaranteed
- * to be at the beginning of the list.
- */
-LIST_INITIALIZE(as_with_asid_head);
 /** Allocate free address space identifier.
+ *
- * This code depends on the fact that ASIDS_ALLOCABLE
+ * Interrupts must be disabled and as_lock must be held
- * is greater than number of supported CPUs.
+ * prior to this call
+ *
  * @return New ASID.
  */
 asid_t asid_get(void)
+{
-    ipl_t ipl;
     asid_t asid;
     link_t *tmp;
     as_t *as;
     /*
      * Check if there is an unallocated ASID.
      */
-    ipl = interrupts_disable();
     spinlock_lock(&asidlock);
     if (asids_allocated == ASIDS_ALLOCABLE) {
         /*
          * All ASIDs are already allocated.
          * Resort to stealing.
          */
         /*
          * Remove the first item on the list.
          * It is guaranteed to belong to an
          * inactive address space.
          */
-        tmp = as_with_asid_head.next;
+        ASSERT(!list_empty(&inactive_as_with_asid_head));
-        ASSERT(tmp != &as_with_asid_head);
+        tmp = inactive_as_with_asid_head.next;
         list_remove(tmp);
-        as = list_get_instance(tmp, as_t, as_with_asid_link);
+        as = list_get_instance(tmp, as_t, inactive_as_with_asid_link);
         spinlock_lock(&as->lock);
         /*
          * Steal the ASID.
          * Note that the stolen ASID is not active.
          */
         asid = as->asid;
         ASSERT(asid != ASID_INVALID);
         /*
          * Notify the address space from wich the ASID
          * was stolen by invalidating its asid member.
          */
         as->asid = ASID_INVALID;
         spinlock_unlock(&as->lock);
         /*
          * Get the system rid of the stolen ASID.
          */
         tlb_shootdown_start(TLB_INVL_ASID, asid, 0, 0);
         tlb_shootdown_finalize();
         tlb_invalidate_asid(asid);
     } else {
         /*
          * There is at least one unallocated ASID.
          * Find it and assign it.
          */
         asid = asid_find_free();
         asids_allocated++;
+    }
     spinlock_unlock(&asidlock);
-    interrupts_restore(ipl);
     return asid;
+}
 /** Release address space identifier.
+ *
  * This code relies on architecture
  * dependent functionality.
+ *
  * @param asid ASID to be released.
  */
 void asid_put(asid_t asid)
+{
     ipl_t ipl;
     ipl = interrupts_disable();
     spinlock_lock(&asidlock);
     asids_allocated--;
     asid_put_arch(asid);
     spinlock_unlock(&asidlock);
-    interrupts_restore(ipl);
-}
-/** Install ASID.
- *
- * This function is to be executed on each address space switch.
- *
- * @param as Address space.
- */
-void asid_install(as_t *as)
-{
-    ipl_t ipl;
-    ipl = interrupts_disable();
-    spinlock_lock(&asidlock);
-    spinlock_lock(&as->lock);
-    if (as->asid != ASID_KERNEL) {
-        if (as->asid != ASID_INVALID) {
-            /*
-             * This address space has valid ASID.
-             * Remove 'as' from the list of address spaces
-             * with assigned ASID, so that it can be later
-             * appended to the tail of the same list.
-             * This is to prevent stealing of ASIDs from
-             * recently installed address spaces.
-             */
-            list_remove(&as->as_with_asid_link);
-        } else {
-            spinlock_unlock(&as->lock);
-            spinlock_unlock(&asidlock);
-            /*
-             * This address space doesn't have ASID assigned.
-             * It was stolen or the address space is being
-             * installed for the first time.
-             * Allocate new ASID for it.
-             */
-            as->asid = asid_get();
-            spinlock_lock(&asidlock);
-            spinlock_lock(&as->lock);
-        }
-        /*
-         * Now it is sure that 'as' has ASID.
-         * It is therefore appended to the list
-         * of address spaces from which it can
-         * be stolen.
-         */
-        list_append(&as->as_with_asid_link, &as_with_asid_head);
-    }
-    spinlock_unlock(&as->lock);
-    spinlock_unlock(&asidlock);
     interrupts_restore(ipl);
+}

Subversion Repositories HelenOS-historic

(root)/kernel/trunk/genarch/src/mm/asid.c – Rev 788 → 823