diff options
| -rw-r--r-- | net/socket.c | 174 |
1 files changed, 76 insertions, 98 deletions
diff --git a/net/socket.c b/net/socket.c index 156f2ef..b5a3fcb 100644 --- a/net/socket.c +++ b/net/socket.c @@ -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; } |
