refcount: correct the documentation

2015-07-14T10:16:51+00:00

The only check that _gf_ref_get() needs is "== 0" for detecting a
failure. The actual return value is not guaranteed to be the number of
active refences (they can change in other threads anyway).

Cherry picked from commit c7f309116d8fa62f6b9fd6ff2902e8ce4bfa192d:
> BUG: 1163543
> Change-Id: I8801601eab37046f5a5ee0bce5a62606115ca151
> Signed-off-by: Niels de Vos 
> Reviewed-on: http://review.gluster.org/11328
> Tested-by: NetBSD Build System 
> Tested-by: Gluster Build System 
> Reviewed-by: Kaleb KEITHLEY 

Change-Id: I8801601eab37046f5a5ee0bce5a62606115ca151
BUG: 1242515
Signed-off-by: Niels de Vos 
Reviewed-on: http://review.gluster.org/11647
Tested-by: NetBSD Build System 
Tested-by: Gluster Build System 
Reviewed-by: Krishnan Parthasarathi

core: add "gf_ref_t" for common refcounting structures

2015-06-27T05:26:24+00:00

Checks for compiler supported atomic operations comes from client_t.h.

An example usage of this change can be found in adding reference
counting to "struct auth_cache_entry" in http://review.gluster.org/11023

Basic usage looks like this:

   #include "refcount.h"

   struct my_struct {
       GF_REF_DECL;
       ... /* more members */
   }

   void my_destructor (void *data)
   {
       struct my_struct *my_ptr = (struct my_struct *) data;

       ... /* do some more cleanups */
       GF_FREE (my_ptr);
   }

   void init_ptr (struct parent *parent)
   {
       struct my_struct *my_ptr = malloc (sizeof (struct my_struct));

       GF_REF_INIT (my_ptr, my_destructor); /* refcount is set to 1 */

       ... /* my_ptr probably gets added to some parent structure */
       parent_add_ptr (parent, my_ptr);
   }

   void do_something (struct parent *parent)
   {
       struct my_struct *my_ptr = NULL;

       /* likely need to lock parent, depends on its access pattern */
       my_ptr = parent_remove_first_ptr (parent);
       /* unlock parent */

       ... /* do something */

       GF_REF_PUT (my_ptr); /* calls my_destructor on refcount = 0 */
   }

URL: http://thread.gmane.org/gmane.comp.file-systems.gluster.devel/11202
Change-Id: Idb98a5861a44c31676108ed8876db12c320912ef
BUG: 1235939
Signed-off-by: Niels de Vos 
Reviewed-on: http://review.gluster.org/11022
Reviewed-by: Xavier Hernandez 
Reviewed-by: Krishnan Parthasarathi 
Tested-by: Gluster Build System 
Tested-by: NetBSD Build System 
(cherry picked from commit ea1d2b0045e2c2ad82a2162a58f9fc36f9d07b20)
Reviewed-on: http://review.gluster.org/11421
Reviewed-by: Raghavendra G 
Tested-by: Raghavendra G

glusterfs.git/libglusterfs/src/refcount.h, branch v3.7.9

refcount: correct the documentation

core: add "gf_ref_t" for common refcounting structures