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From d58f0ac175e0506a9e76e4197497be20337e444d Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Tue, 6 May 2014 18:58:10 +0200
Subject: [PATCH 06/16] libdiskfs: lock-less reference counting for peropen
objects
* libdiskfs/diskfs.h (struct peropen): Use refcount_t for field refcnt.
* libdiskfs/peropen-make.c (diskfs_make_peropen): Initialize refcnt.
* libdiskfs/peropen-rele.c (diskfs_release_peropen): Adjust accordingly.
* libdiskfs/protid-make.c (diskfs_start_protid): Likewise. Also, the
node must no longer be locked, adjust comment accordingly.
(diskfs_create_protid): Likewise.
---
libdiskfs/diskfs.h | 7 ++++---
libdiskfs/peropen-make.c | 2 +-
libdiskfs/peropen-rele.c | 21 ++++++++++-----------
libdiskfs/protid-make.c | 8 ++++----
4 files changed, 19 insertions(+), 19 deletions(-)
diff --git a/libdiskfs/diskfs.h b/libdiskfs/diskfs.h
index a3f860d..acd1910 100644
--- a/libdiskfs/diskfs.h
+++ b/libdiskfs/diskfs.h
@@ -28,6 +28,7 @@
#include <hurd/iohelp.h>
#include <idvec.h>
#include <features.h>
+#include <refcount.h>
#ifdef DISKFS_DEFINE_EXTERN_INLINE
#define DISKFS_EXTERN_INLINE
@@ -57,7 +58,7 @@ struct peropen
{
int filepointer;
int lock_status;
- int refcnt;
+ refcount_t refcnt;
int openstat;
struct node *np;
@@ -817,12 +818,12 @@ diskfs_create_node (struct node *dir, const char *name, mode_t mode,
struct dirstat *ds);
/* Create and return a protid for an existing peropen PO in CRED,
- referring to user USER. The node PO->np must be locked. */
+ referring to user USER. */
error_t diskfs_create_protid (struct peropen *po, struct iouser *user,
struct protid **cred);
/* Build and return in CRED a protid which has no user identification, for
- peropen PO. The node PO->np must be locked. */
+ peropen PO. */
error_t diskfs_start_protid (struct peropen *po, struct protid **cred);
/* Finish building protid CRED started with diskfs_start_protid;
diff --git a/libdiskfs/peropen-make.c b/libdiskfs/peropen-make.c
index eba037f..6d5ca01 100644
--- a/libdiskfs/peropen-make.c
+++ b/libdiskfs/peropen-make.c
@@ -31,7 +31,7 @@ diskfs_make_peropen (struct node *np, int flags, struct peropen *context,
po->filepointer = 0;
po->lock_status = LOCK_UN;
- po->refcnt = 0;
+ refcount_init (&po->refcnt, 0);
po->openstat = flags;
po->np = np;
po->path = NULL;
diff --git a/libdiskfs/peropen-rele.c b/libdiskfs/peropen-rele.c
index d3f7492..877137b 100644
--- a/libdiskfs/peropen-rele.c
+++ b/libdiskfs/peropen-rele.c
@@ -22,13 +22,8 @@
void
diskfs_release_peropen (struct peropen *po)
{
- pthread_mutex_lock (&po->np->lock);
-
- if (--po->refcnt)
- {
- pthread_mutex_unlock (&po->np->lock);
- return;
- }
+ if (refcount_deref (&po->refcnt) > 0)
+ return;
if (po->root_parent)
mach_port_deallocate (mach_task_self (), po->root_parent);
@@ -40,10 +35,14 @@ diskfs_release_peropen (struct peropen *po)
mach_port_deallocate (mach_task_self (), po->shadow_root_parent);
if (po->lock_status != LOCK_UN)
- fshelp_acquire_lock (&po->np->userlock, &po->lock_status,
- &po->np->lock, LOCK_UN);
-
- diskfs_nput (po->np);
+ {
+ pthread_mutex_lock (&po->np->lock);
+ fshelp_acquire_lock (&po->np->userlock, &po->lock_status,
+ &po->np->lock, LOCK_UN);
+ diskfs_nput (po->np);
+ }
+ else
+ diskfs_nrele (po->np);
free (po->path);
free (po);
diff --git a/libdiskfs/protid-make.c b/libdiskfs/protid-make.c
index b39b92a..22aaa2e 100644
--- a/libdiskfs/protid-make.c
+++ b/libdiskfs/protid-make.c
@@ -20,7 +20,7 @@
#include <assert.h>
/* Build and return in CRED a protid which has no user identification, for
- peropen PO. The node PO->np must be locked. */
+ peropen PO. */
error_t
diskfs_start_protid (struct peropen *po, struct protid **cred)
{
@@ -29,7 +29,7 @@ diskfs_start_protid (struct peropen *po, struct protid **cred)
sizeof (struct protid), cred);
if (! err)
{
- po->refcnt++;
+ refcount_ref (&po->refcnt);
(*cred)->po = po;
(*cred)->shared_object = MACH_PORT_NULL;
(*cred)->mapped = 0;
@@ -55,8 +55,8 @@ diskfs_finish_protid (struct protid *cred, struct iouser *user)
assert_perror (err);
}
-/* Create and return a protid for an existing peropen PO in CRED for USER.
- The node PO->np must be locked. */
+/* Create and return a protid for an existing peropen PO in CRED for
+ USER. */
error_t
diskfs_create_protid (struct peropen *po, struct iouser *user,
struct protid **cred)
--
2.0.0.rc2
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