diff options
author | Niels de Vos <ndevos@redhat.com> | 2015-05-31 15:16:41 +0200 |
---|---|---|
committer | Niels de Vos <ndevos@redhat.com> | 2015-06-20 05:01:43 -0700 |
commit | ea1d2b0045e2c2ad82a2162a58f9fc36f9d07b20 (patch) | |
tree | 986f6c3039c26e0d4547b1ddde8b0f324270113d /libglusterfs/src/refcount.c | |
parent | f460d1c9a2d83b24500c574aabce75438bdc8f9d (diff) |
core: add "gf_ref_t" for common refcounting structures
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: 1228157
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Reviewed-on: http://review.gluster.org/11022
Reviewed-by: Xavier Hernandez <xhernandez@datalab.es>
Reviewed-by: Krishnan Parthasarathi <kparthas@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Tested-by: NetBSD Build System <jenkins@build.gluster.org>
Diffstat (limited to 'libglusterfs/src/refcount.c')
-rw-r--r-- | libglusterfs/src/refcount.c | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/libglusterfs/src/refcount.c b/libglusterfs/src/refcount.c new file mode 100644 index 00000000000..96edc10982a --- /dev/null +++ b/libglusterfs/src/refcount.c @@ -0,0 +1,112 @@ +/* + Copyright (c) 2015 Red Hat, Inc. <http://www.redhat.com> + This file is part of GlusterFS. + + This file is licensed to you under your choice of the GNU Lesser + General Public License, version 3 or any later version (LGPLv3 or + later), or the GNU General Public License, version 2 (GPLv2), in all + cases as published by the Free Software Foundation. +*/ + +#include "common-utils.h" +#include "refcount.h" + +#ifndef REFCOUNT_NEEDS_LOCK + +unsigned int +_gf_ref_get (gf_ref_t *ref) +{ + unsigned int cnt = __sync_fetch_and_add (&ref->cnt, 1); + + /* if cnt == 0, we're in a fatal position, the object will be free'd + * + * There is a race when two threads do a _gf_ref_get(). Only one of + * them may get a 0 returned. That is acceptible, because one + * _gf_ref_get() returning 0 should be handled as a fatal problem and + * when correct usage/locking is used, it should never happen. + */ + GF_ASSERT (cnt != 0); + + return cnt; +} + +unsigned int +_gf_ref_put (gf_ref_t *ref) +{ + unsigned int cnt = __sync_fetch_and_sub (&ref->cnt, 1); + + /* if cnt == 1, the last user just did a _gf_ref_put() + * + * When cnt == 0, one _gf_ref_put() was done too much and there has + * been a thread using the refcounted structure when it was not + * supposed to. + */ + GF_ASSERT (cnt != 0); + + if (cnt == 1 && ref->release) { + ref->release (ref->data); + /* set return value to 0 to inform the caller correctly */ + cnt = 0; + } + + return cnt; +} + +#else + +unsigned int +_gf_ref_get (gf_ref_t *ref) +{ + unsigned int cnt = 0; + + LOCK (&ref->lk); + { + /* never can be 0, should have been free'd */ + if (ref->cnt > 0) + cnt = ++ref->cnt; + else + GF_ASSERT (ref->cnt > 0); + } + UNLOCK (&ref->lk); + + return cnt; +} + +unsigned int +_gf_ref_put (gf_ref_t *ref) +{ + unsigned int cnt = 0; + int release = 0; + + LOCK (&ref->lk); + { + if (ref->cnt != 0) { + cnt = --ref->cnt; + /* call release() only when cnt == 0 */ + release = (cnt == 0); + } else + GF_ASSERT (ref->cnt != 0); + } + UNLOCK (&ref->lk); + + if (release && ref->release) + ref->release (ref->data); + + return cnt; +} + +#endif /* REFCOUNT_NEEDS_LOCK */ + + +void +_gf_ref_init (gf_ref_t *ref, gf_ref_release_t release, void *data) +{ + GF_ASSERT (ref); + +#ifdef REFCOUNT_NEEDS_LOCK + LOCK_INIT (&ref->lk); +#endif + ref->cnt = 1; + ref->release = release; + ref->data = data; +} |