Changeset fbcdeb8 in mainline for uspace/lib/c/generic/malloc.c

Timestamp:

2011-12-19T17:30:39Z (12 years ago)

Author:

Martin Decky <martin@…>

Branches:

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

Children:

58f6229

Parents:

24cf31f1

Message:

Remove the two-phase way of creating virtual memory areas (first asking for a mappable address and then mapping it) which was prone to race conditions when two or more calls to as_get_mappable_page() and as_area_create() were interleaved. This for example caused the e1k driver to randomly fail.

The memory area related syscalls and IPC calls have all been altered to accept a special value (void *) -1, representing a demand to atomically search for a mappable address space "hole" and map to it.

Individual changes:

• IPC_M_SHARE_OUT: the destination address space area is supplied by the kernel, the callee only specifies the lower bound

(the address is returned to the callee via a pointer in an IPC reply argument)

• IPC_M_SHARE_IN: the destination address space ares is supplied by the kernel, the callee only specifies the lower bound

(the address is returned to the caller as usual via an IPC argument)

• SYS_AS_GET_UNMAPPED_AREA was removed
• dummy implementations of SYS_PHYSMEM_UNMAP and SYS_IOSPACE_DISABLE were added for the sake of symmetry (they do nothing yet)
• SYS_PHYSMEM_MAP and SYS_DMAMEM_MAP were altered to accept (void *) -1 as address space area base and a lower bound
• kernel as_area_create() and as_area_share() were altered to accept (void *) -1 as address space area base and a lower bound
• uspace libraries and programs were altered to reflect the new API

File:

• uspace/lib/c/generic/malloc.c (modified) (1 diff)

uspace/lib/c/generic/malloc.c

@@ -283 +283 @@
 static bool area_create(size_t size)
 {
-        void *start = as_get_mappable_page(size);
-        if (start == NULL)
-                return false;
-        
-        /* Align the heap area on page boundary */
-        void *astart = (void *) ALIGN_UP((uintptr_t) start, PAGE_SIZE);
+        /* Align the heap area size on page boundary */
         size_t asize = ALIGN_UP(size, PAGE_SIZE);
-        
-        astart = as_area_create(astart, asize, AS_AREA_WRITE | AS_AREA_READ);
+        void *astart = as_area_create((void *) -1, asize,
+            AS_AREA_WRITE | AS_AREA_READ);
         if (astart == (void *) -1)
                 return false;