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[NET]: socket family using RCU 

Replace the gross custom locking done in socket code for net_family[]
with simple RCU usage. Some reordering necessary to avoid sleep issues
with sock_alloc.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2006-09-01 00:23:39 -07:00 committed by David S. Miller
parent 757dbb494b
commit 55737fda0b
1 changed files with 76 additions and 98 deletions
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174
net/socket.c
View File

@ -59,11 +59,11 @@
*/
#include <linux/mm.h>
#include <linux/smp_lock.h>
#include <linux/socket.h>
#include <linux/file.h>
#include <linux/net.h>
#include <linux/interrupt.h>
#include <linux/rcupdate.h>
#include <linux/netdevice.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
@ -146,51 +146,8 @@ static struct file_operations socket_file_ops = {
* The protocol list. Each protocol is registered in here.
*/
static struct net_proto_family *net_families[NPROTO];
#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
static atomic_t net_family_lockct = ATOMIC_INIT(0);
static DEFINE_SPINLOCK(net_family_lock);
/* The strategy is: modifications net_family vector are short, do not
sleep and veeery rare, but read access should be free of any exclusive
locks.
*/
static void net_family_write_lock(void)
{
spin_lock(&net_family_lock);
while (atomic_read(&net_family_lockct) != 0) {
spin_unlock(&net_family_lock);
yield();
spin_lock(&net_family_lock);
}
}
static __inline__ void net_family_write_unlock(void)
{
spin_unlock(&net_family_lock);
}
static __inline__ void net_family_read_lock(void)
{
atomic_inc(&net_family_lockct);
spin_unlock_wait(&net_family_lock);
}
static __inline__ void net_family_read_unlock(void)
{
atomic_dec(&net_family_lockct);
}
#else
#define net_family_write_lock() do { } while(0)
#define net_family_write_unlock() do { } while(0)
#define net_family_read_lock() do { } while(0)
#define net_family_read_unlock() do { } while(0)
#endif
static const struct net_proto_family *net_families[NPROTO];
/*
* Statistics counters of the socket lists
@ -1138,6 +1095,7 @@ static int __sock_create(int family, int type, int protocol,
{
int err;
struct socket *sock;
const struct net_proto_family *pf;
/*
* Check protocol is in range
@ -1166,6 +1124,21 @@ static int __sock_create(int family, int type, int protocol,
if (err)
return err;
/*
* Allocate the socket and allow the family to set things up. if
* the protocol is 0, the family is instructed to select an appropriate
* default.
*/
sock = sock_alloc();
if (!sock) {
if (net_ratelimit())
printk(KERN_WARNING "socket: no more sockets\n");
return -ENFILE; /* Not exactly a match, but its the
closest posix thing */
}
sock->type = type;
#if defined(CONFIG_KMOD)
/* Attempt to load a protocol module if the find failed.
*
@ -1173,72 +1146,61 @@ static int __sock_create(int family, int type, int protocol,
* requested real, full-featured networking support upon configuration.
* Otherwise module support will break!
*/
if (net_families[family] == NULL) {
if (net_families[family] == NULL)
request_module("net-pf-%d", family);
}
#endif
net_family_read_lock();
if (net_families[family] == NULL) {
err = -EAFNOSUPPORT;
goto out;
}
/*
* Allocate the socket and allow the family to set things up. if
* the protocol is 0, the family is instructed to select an appropriate
* default.
*/
if (!(sock = sock_alloc())) {
if (net_ratelimit())
printk(KERN_WARNING "socket: no more sockets\n");
err = -ENFILE; /* Not exactly a match, but its the
closest posix thing */
goto out;
}
sock->type = type;
rcu_read_lock();
pf = rcu_dereference(net_families[family]);
err = -EAFNOSUPPORT;
if (!pf)
goto out_release;
/*
* We will call the ->create function, that possibly is in a loadable
* module, so we have to bump that loadable module refcnt first.
*/
err = -EAFNOSUPPORT;
if (!try_module_get(net_families[family]->owner))
if (!try_module_get(pf->owner))
goto out_release;
if ((err = net_families[family]->create(sock, protocol)) < 0) {
sock->ops = NULL;
/* Now protected by module ref count */
rcu_read_unlock();
err = pf->create(sock, protocol);
if (err < 0)
goto out_module_put;
}
/*
* Now to bump the refcnt of the [loadable] module that owns this
* socket at sock_release time we decrement its refcnt.
*/
if (!try_module_get(sock->ops->owner)) {
sock->ops = NULL;
goto out_module_put;
}
if (!try_module_get(sock->ops->owner))
goto out_module_busy;
/*
* Now that we're done with the ->create function, the [loadable]
* module can have its refcnt decremented
*/
module_put(net_families[family]->owner);
*res = sock;
module_put(pf->owner);
err = security_socket_post_create(sock, family, type, protocol, kern);
if (err)
goto out_release;
*res = sock;
out:
net_family_read_unlock();
return err;
return 0;
out_module_busy:
err = -EAFNOSUPPORT;
out_module_put:
module_put(net_families[family]->owner);
out_release:
sock->ops = NULL;
module_put(pf->owner);
out_sock_release:
sock_release(sock);
goto out;
return err;
out_release:
rcu_read_unlock();
goto out_sock_release;
}
int sock_create(int family, int type, int protocol, struct socket **res)
@ -2109,12 +2071,15 @@ asmlinkage long sys_socketcall(int call, unsigned long __user *args)
#endif /* __ARCH_WANT_SYS_SOCKETCALL */
/*
/**
* sock_register - add a socket protocol handler
* @ops: description of protocol
*
* This function is called by a protocol handler that wants to
* advertise its address family, and have it linked into the
* SOCKET module.
* socket interface. The value ops->family coresponds to the
* socket system call protocol family.
*/
int sock_register(struct net_proto_family *ops)
{
int err;
@ -2124,31 +2089,44 @@ int sock_register(struct net_proto_family *ops)
NPROTO);
return -ENOBUFS;
}
net_family_write_lock();
err = -EEXIST;
if (net_families[ops->family] == NULL) {
spin_lock(&net_family_lock);
if (net_families[ops->family])
err = -EEXIST;
else {
net_families[ops->family] = ops;
err = 0;
}
net_family_write_unlock();
spin_unlock(&net_family_lock);
printk(KERN_INFO "NET: Registered protocol family %d\n", ops->family);
return err;
}
/*
/**
* sock_unregister - remove a protocol handler
* @family: protocol family to remove
*
* This function is called by a protocol handler that wants to
* remove its address family, and have it unlinked from the
* SOCKET module.
* new socket creation.
*
* If protocol handler is a module, then it can use module reference
* counts to protect against new references. If protocol handler is not
* a module then it needs to provide its own protection in
* the ops->create routine.
*/
int sock_unregister(int family)
{
if (family < 0 || family >= NPROTO)
return -1;
return -EINVAL;
net_family_write_lock();
spin_lock(&net_family_lock);
net_families[family] = NULL;
net_family_write_unlock();
spin_unlock(&net_family_lock);
synchronize_rcu();
printk(KERN_INFO "NET: Unregistered protocol family %d\n", family);
return 0;
}