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From c4bd59b5b1bda56338215fd509e9414ec8c7f052 Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Tue, 6 May 2014 19:07:13 +0200
Subject: [PATCH 07/15] libtrivfs: lock-less reference counting for
trivfs_peropen objects
* libtrivfs/trivfs.h (struct trivfs_peropen): Use refcount_t for field
refcnt.
(struct trivfs_control): Remove unused field lock.
* libtrivfs/cntl-create.c (trivfs_create_control): Drop the mutex
initialization.
* libtrivfs/io-reauthenticate.c (trivfs_S_io_reauthenticate): Adjust
accordingly.
* libtrivfs/io-restrict-auth.c (trivfs_S_io_restrict_auth): Likewise.
* libtrivfs/open.c (trivfs_open): Initialize refcnt.
* libtrivfs/protid-clean.c (trivfs_clean_protid): Likewise.
* libtrivfs/protid-dup.c (trivfs_protid_dup): Likewise.
---
libtrivfs/cntl-create.c | 1 -
libtrivfs/io-reauthenticate.c | 5 +----
libtrivfs/io-restrict-auth.c | 4 +---
libtrivfs/open.c | 2 +-
libtrivfs/protid-clean.c | 26 +++++++++++++++-----------
libtrivfs/protid-dup.c | 5 +----
libtrivfs/trivfs.h | 4 ++--
7 files changed, 21 insertions(+), 26 deletions(-)
diff --git a/libtrivfs/cntl-create.c b/libtrivfs/cntl-create.c
index 910daf3..eb9a834 100644
--- a/libtrivfs/cntl-create.c
+++ b/libtrivfs/cntl-create.c
@@ -85,7 +85,6 @@ trivfs_create_control (mach_port_t underlying,
}
(*control)->hook = 0;
- pthread_mutex_init (&(*control)->lock, NULL);
}
out:
diff --git a/libtrivfs/io-reauthenticate.c b/libtrivfs/io-reauthenticate.c
index 7677697..df0ed2e 100644
--- a/libtrivfs/io-reauthenticate.c
+++ b/libtrivfs/io-reauthenticate.c
@@ -62,11 +62,8 @@ trivfs_S_io_reauthenticate (struct trivfs_protid *cred,
newcred->isroot = 1;
newcred->hook = cred->hook;
-
- pthread_mutex_lock (&cred->po->cntl->lock);
newcred->po = cred->po;
- newcred->po->refcnt++;
- pthread_mutex_unlock (&cred->po->cntl->lock);
+ refcount_ref (&newcred->po->refcnt);
do
err = io_restrict_auth (newcred->po->cntl->underlying, &newcred->realnode,
diff --git a/libtrivfs/io-restrict-auth.c b/libtrivfs/io-restrict-auth.c
index 65b4fd6..39670fe 100644
--- a/libtrivfs/io-restrict-auth.c
+++ b/libtrivfs/io-restrict-auth.c
@@ -110,10 +110,8 @@ trivfs_S_io_restrict_auth (struct trivfs_protid *cred,
}
newcred->isroot = 0;
- pthread_mutex_lock (&cred->po->cntl->lock);
newcred->po = cred->po;
- newcred->po->refcnt++;
- pthread_mutex_unlock (&cred->po->cntl->lock);
+ refcount_ref (&newcred->po->refcnt);
if (cred->isroot && idvec_contains (user->uids, 0))
newcred->isroot = 1;
newcred->user = user;
diff --git a/libtrivfs/open.c b/libtrivfs/open.c
index f64d2ff..97e70a1 100644
--- a/libtrivfs/open.c
+++ b/libtrivfs/open.c
@@ -40,7 +40,7 @@ trivfs_open (struct trivfs_control *cntl,
ports_port_ref (cntl);
- po->refcnt = 1;
+ refcount_init (&po->refcnt, 1);
po->cntl = cntl;
po->openmodes = flags;
po->hook = 0;
diff --git a/libtrivfs/protid-clean.c b/libtrivfs/protid-clean.c
index f98da6a..cce736d 100644
--- a/libtrivfs/protid-clean.c
+++ b/libtrivfs/protid-clean.c
@@ -31,19 +31,23 @@ trivfs_clean_protid (void *arg)
(*trivfs_protid_destroy_hook) (cred);
/* If we hold the only reference to the peropen, try to get rid of it. */
- pthread_mutex_lock (&cntl->lock);
- if (cred->po->refcnt == 1 && trivfs_peropen_destroy_hook)
+ if (refcount_deref (&cred->po->refcnt) == 0)
{
- pthread_mutex_unlock (&cntl->lock);
- (*trivfs_peropen_destroy_hook) (cred->po);
- pthread_mutex_lock (&cntl->lock);
+ if (trivfs_peropen_destroy_hook)
+ {
+ /* Reaquire a reference while we call the hook. */
+ refcount_ref (&cred->po->refcnt);
+ (*trivfs_peropen_destroy_hook) (cred->po);
+ if (refcount_deref (&cred->po->refcnt) == 0)
+ goto free_po;
+ }
+ else
+ {
+ free_po:
+ ports_port_deref (cntl);
+ free (cred->po);
+ }
}
- if (--cred->po->refcnt == 0)
- {
- ports_port_deref (cntl);
- free (cred->po);
- }
- pthread_mutex_unlock (&cntl->lock);
iohelp_free_iouser (cred->user);
diff --git a/libtrivfs/protid-dup.c b/libtrivfs/protid-dup.c
index 6169603..75f3ca8 100644
--- a/libtrivfs/protid-dup.c
+++ b/libtrivfs/protid-dup.c
@@ -35,11 +35,8 @@ trivfs_protid_dup (struct trivfs_protid *cred, struct trivfs_protid **dup)
if (! err)
{
- pthread_mutex_lock (&cred->po->cntl->lock);
new->po = cred->po;
- new->po->refcnt++;
- pthread_mutex_unlock (&cred->po->cntl->lock);
-
+ refcount_ref (&new->po->refcnt);
new->isroot = cred->isroot;
err = iohelp_dup_iouser (&new->user, cred->user);
diff --git a/libtrivfs/trivfs.h b/libtrivfs/trivfs.h
index bb456ff..8902338 100644
--- a/libtrivfs/trivfs.h
+++ b/libtrivfs/trivfs.h
@@ -24,6 +24,7 @@
#include <mach/mach.h>
#include <hurd/ports.h>
#include <hurd/iohelp.h>
+#include <refcount.h>
struct trivfs_protid
{
@@ -41,14 +42,13 @@ struct trivfs_peropen
{
void *hook; /* for user use */
int openmodes;
- int refcnt;
+ refcount_t refcnt;
struct trivfs_control *cntl;
};
struct trivfs_control
{
struct port_info pi;
- pthread_mutex_t lock;
struct port_class *protid_class;
struct port_bucket *protid_bucket;
mach_port_t filesys_id;
--
2.0.0.rc0
|
