Re: [Xenomai-core] rt_heap in userspace, heapsize [patch]

[Stefan Kisdaroczi <kisda@domain.hid>]

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Hi again,

I looked at the sources now...

Am Tuesday 17 January 2006 14:57 schrieb Stefan Kisdaroczi:
> Hi,
>
> I made a small test with rt_heap_ in userspace,
> i think I understood the actual limitations of the userspace support.
> I used 10000 as heapsize. Xenomai 2.1-RC2/x86.
>
> This should alloc the entire heap, according to the API documentation:
> rt_heap_create( ..., ..., 10000, ... )
> rt_heap_alloc( ..., 10000, ..., .... ) -> This call fails, but it should
> work
API documentation: "If the heap is shared, this value can be either zero, or 
the same value given to rt_heap_create()."

Looking at the code, calculating the right value can be tricky and would 
depend on xeno-internals. rt_heap_inquire would be another way to get it.

Only accepting 0 would be less confusing. See (untested) patch as as 
suggestion.

> Using heapsize 0 it works:
> rt_heap_create( ..., ..., 10000, ... )
> rt_heap_alloc( ..., 0, ..., .... )
>
> rt_heap_inquire shows a heapsize of 12228 (IIRC).
> So, this would probably work (untested):
> rt_heap_create( ..., ..., 10000, ... )
> rt_heap_alloc( ..., 12228, ..., .... )
>
> The 2228 bytes difference seems to be the space needed for the heap control
> structures.
>
> I think the following should be fixed:
> 1) rt_create_alloc should alter the heapsize the same as rt_heap_create
> does 
Makes no sense, after looking at the code.

> > 2) rt_heap_inquire should return the _real_ heapsize 
The real heap space can be bigger than the requested, so this can happen.

thx again
kisda

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Index: include/native/heap.h
===================================================================
--- include/native/heap.h	(Revision 465)
+++ include/native/heap.h	(Arbeitskopie)
@@ -32,6 +32,9 @@
 #define H_DMA    0x100		/* Use memory suitable for DMA. */
 #define H_SHARED 0x200		/* Use mappable shared memory. */
 
+/* Operation flags. */
+#define H_ALL    0x0	        /* Entire heap space. */
+
 typedef struct rt_heap_info {
 
     int nwaiters;		/* !< Number of pending tasks. */
Index: ksrc/skins/native/heap.c
===================================================================
--- ksrc/skins/native/heap.c	(Revision 465)
+++ ksrc/skins/native/heap.c	(Arbeitskopie)
@@ -410,10 +410,9 @@
  * from.
  *
  * @param size The requested size in bytes of the block. If the heap
- * is shared, this value can be either zero, or the same value given
- * to rt_heap_create(). In any case, the same block covering the
- * entire heap space will always be returned to all callers of this
- * service.
+ * is shared, H_ALL should be passed, as always the same block
+ * covering the entire heap space will be returned to all callers of
+ * this service.
  *
  * @param timeout The number of clock ticks to wait for a block of
  * sufficient size to be available from a local heap (see
@@ -432,8 +431,7 @@
  * @return 0 is returned upon success. Otherwise:
  *
  * - -EINVAL is returned if @a heap is not a heap descriptor, or @a
- * heap is shared (i.e. H_SHARED mode) and @a size is non-zero but
- * does not match the actual heap size passed to rt_heap_create().
+ * heap is shared (i.e. H_SHARED mode) and @a size is not H_ALL.
  *
  * - -EIDRM is returned if @a heap is a deleted heap descriptor.
  *
@@ -503,12 +501,7 @@
 
 	if (!block)
 	    {
-	    /* It's ok to pass zero for size here, since the requested
-	       size is implicitely the whole heap space; but if
-	       non-zero is given, it must match the actual heap
-	       size. */
-
-	    if (size > 0 && size != xnheap_size(&heap->heap_base))
+	    if (size != H_ALL)
 		{
 		err = -EINVAL;
 		goto unlock_and_exit;

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