Changeset 692bd3f2 in mainline

Timestamp:

2012-11-06T22:51:56Z (12 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

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

Children:

1107050

Parents:

338810f

Message:

Define AS_AREA_NORESERVE and allow its use in the anonymous backend.

• NORESERVE areas do not reserve physical memory in advance.
• NORESERVE areas do not block while waiting for physical memory.
• if a NORESERVE area cannot allocate a page of physical memory, it kills the task instantly

Files:

• abi/include/mm/as.h (modified) (1 diff)
• kernel/generic/src/mm/backend_anon.c (modified) (6 diffs)

abi/include/mm/as.h

@@ -42 +42 @@
 #define AS_AREA_CACHEABLE  0x08
 #define AS_AREA_GUARD      0x10
+#define AS_AREA_NORESERVE  0x20
 
 /** Address space area info exported to uspace. */

kernel/generic/src/mm/backend_anon.c

@@ -74 +74 @@
 bool anon_create(as_area_t *area)
 {
+        if (area->flags & AS_AREA_NORESERVE)
+                return true;
+
         return reserve_try_alloc(area->pages);
 }
@@ -79 +82 @@
 bool anon_resize(as_area_t *area, size_t new_pages)
 {
+        if (area->flags & AS_AREA_NORESERVE)
+                return true;
+
         if (new_pages > area->pages)
                 return reserve_try_alloc(new_pages - area->pages);
@@ -100 +106 @@
         ASSERT(mutex_locked(&area->as->lock));
         ASSERT(mutex_locked(&area->lock));
+        ASSERT(!(area->flags & AS_AREA_NORESERVE));
 
         /*
@@ -139 +146 @@
 void anon_destroy(as_area_t *area)
 {
+        if (area->flags & AS_AREA_NORESERVE)
+                return;
+
         reserve_free(area->pages);
 }
@@ -225 +235 @@
                  *   the different causes
                  */
-                kpage = km_temporary_page_get(&frame, FRAME_NO_RESERVE);
+
+                unsigned int flags;
+
+                if (area->flags & AS_AREA_NORESERVE) {
+                        /*
+                         * This is a NORESERVE area, which means that no
+                         * physical memory has been reserved beforehands.
+                         * We therefore need to make an atomic and reserving
+                         * allocation.
+                         */
+                        flags = FRAME_ATOMIC;
+                } else {
+                        /*
+                         * The physical memory has already been reserved
+                         * when this part of the area was created. Avoid
+                         * double reservation by using the appropriate flag.
+                         */
+                        flags = FRAME_NO_RESERVE;
+                }
+
+                kpage = km_temporary_page_get(&frame, flags);
+                if (!kpage)
+                        return AS_PF_FAULT;
                 memsetb((void *) kpage, PAGE_SIZE, 0);
                 km_temporary_page_put(kpage);
@@ -255 +287 @@
         ASSERT(mutex_locked(&area->lock));
 
-        frame_free_noreserve(frame);
+        if (area->flags & AS_AREA_NORESERVE) {
+                /*
+                 * In case of the NORESERVE areas, physical memory will not be
+                 * unreserved when the area is destroyed so we need to use the
+                 * normal unreserving frame_free().
+                 */
+                frame_free(frame);
+        } else {
+                /*
+                 * The reserve will be given back when the area is destroyed or
+                 * resized, so use the frame_free_noreserve() which does not
+                 * manipulate the reserve or it would be given back twice.
+                 */
+                frame_free_noreserve(frame);
+        }
 }