library: minimize the use of 'cleanup_stacks' routines

Some parts of our newlib implementation are the result
of functions which have been propagated from module to
module. In particular, those 'cleanup_stacks' routines
are all similar & likely originated in the <pids> api.

In that interface there was a need to free dynamically
acquired memory before the result structure was reused
to satisfy subsequent 'get', 'select' or 'reap' calls.
This, in turn, led to a concept of 'dirty' stacks with
the need to call one of two 'cleanup_stack' functions.

None of the remaining interfaces deal with such memory
yet they each had their own 'cleanup_stack' functions.
Those functions were responsible for resetting each of
the result unions to zero, excluding any 'noop' items.

The bottom line is that for all interfaces, repetitive
calls would require iterating through the stack(s) two
separate times: once to 'cleanup' another to 'assign'.

With this commit we will reduce iterations to just the
'assign' routine. A reset to zero will be accomplished
in the 'extra' item set routine (which is the only one
actually requiring any reset). All other items will be
reinitialized automatically by a new current set value
or upon reallocation when an items compliment changes.

In the <pids> interface, any freeing of dynamic memory
could have been accomplished by adding that 'freefunc'
check to the 'assign' function. However, that requires
an Item_table test with every item. Instead, we'll now
satisfy such needs as the very first step in those set
functions responsible for dynamically acquired memory.

[ the <pids> api retains 2 'cleanup_stack' functions ]
[ to accommodate stack(s) 'reset' & to serve 'unref' ]

Lastly, all the 'itemize_stack' functions were tweaked
by eliminating an unnecessary initialization of result
unions. That objective was already accomplished by the
calloc() in a 'stacks_alloc' function or the remaining
'cleanup_stack' routine found in the <pids> interface.

Signed-off-by: Jim Warner <james.warner@comcast.net>

proc/diskstats.c

@@ -85,7 +85,6 @@ struct ext_support {
     int numitems;                      // includes 'logical_end' delimiter
     enum diskstats_item *items;        // includes 'logical_end' delimiter
     struct stacks_extent *extents;     // anchor for these extents
-    int dirty_stacks;
 };
 
 struct fetch_support {
@@ -122,7 +121,7 @@ struct diskstats_info {
 #define HST_set(e,t,x) setDECL(e) { R->result. t = ( N->new . x - N->old. x ); }
 
 setDECL(noop)  { (void)R; (void)N; }
-setDECL(extra) { (void)R; (void)N; }
+setDECL(extra) { (void)N; R->result.ul_int = 0; }
 
 DEV_set(DISKSTATS_NAME,                 str,     name)
 DEV_set(DISKSTATS_TYPE,                 s_int,   type)
@@ -429,34 +428,6 @@ static inline void diskstats_assign_results (
 } // end: diskstats_assign_results
 
 
-static inline void diskstats_cleanup_stack (
-        struct diskstats_result *this)
-{
-    for (;;) {
-        if (this->item >= DISKSTATS_logical_end)
-            break;
-        if (this->item > DISKSTATS_noop)
-            this->result.ul_int = 0;
-        ++this;
-    }
-} // end: diskstats_cleanup_stack
-
-
-static inline void diskstats_cleanup_stacks_all (
-        struct ext_support *this)
-{
-    struct stacks_extent *ext = this->extents;
-    int i;
-
-    while (ext) {
-        for (i = 0; ext->stacks[i]; i++)
-            diskstats_cleanup_stack(ext->stacks[i]->head);
-        ext = ext->next;
-    };
-    this->dirty_stacks = 0;
-} // end: diskstats_cleanup_stacks_all
-
-
 static void diskstats_extents_free_all (
         struct ext_support *this)
 {
@@ -478,7 +449,6 @@ static inline struct diskstats_result *diskstats_itemize_stack (
 
     for (i = 0; i < depth; i++) {
         p->item = items[i];
-        p->result.ul_int = 0;
         ++p;
     }
     return p_sav;
@@ -653,7 +623,6 @@ static int diskstats_stacks_fetch (
             return -1;       // here, errno was set to ENOMEM
         memcpy(info->fetch.anchor, ext->stacks, sizeof(void *) * n_alloc);
     }
-    diskstats_cleanup_stacks_all(&info->fetch_ext);
 
     // iterate stuff --------------------------------------
     n_inuse = 0;
@@ -872,14 +841,10 @@ PROCPS_EXPORT struct diskstats_reap *procps_diskstats_reap (
         return NULL;         // here, errno may be overridden with ENOMEM
     errno = 0;
 
-    if (info->fetch_ext.dirty_stacks)
-        diskstats_cleanup_stacks_all(&info->fetch_ext);
-
     if (diskstats_read_failed(info))
         return NULL;
     if (0 > diskstats_stacks_fetch(info))
         return NULL;
-    info->fetch_ext.dirty_stacks = 1;
 
     return &info->fetch.results;
 } // end: procps_diskstats_reap
@@ -911,9 +876,6 @@ PROCPS_EXPORT struct diskstats_stack *procps_diskstats_select (
     && (!diskstats_stacks_alloc(&info->select_ext, 1)))
        return NULL;
 
-    if (info->select_ext.dirty_stacks)
-        diskstats_cleanup_stacks_all(&info->select_ext);
-
     if (diskstats_read_failed(info))
         return NULL;
     if (!(node = node_get(info, name))) {
@@ -922,7 +884,6 @@ PROCPS_EXPORT struct diskstats_stack *procps_diskstats_select (
     }
 
     diskstats_assign_results(info->select_ext.extents->stacks[0], node);
-    info->select_ext.dirty_stacks = 1;
 
     return info->select_ext.extents->stacks[0];
 } // end: procps_diskstats_select