diff options
Diffstat (limited to 'ipc/util.c')
| -rw-r--r-- | ipc/util.c | 129 |
1 files changed, 57 insertions, 72 deletions
diff --git a/ipc/util.c b/ipc/util.c index 4704223bfad4..7684f41bce76 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -15,6 +15,29 @@ * Jun 2006 - namespaces ssupport * OpenVZ, SWsoft Inc. * Pavel Emelianov <xemul@openvz.org> + * + * General sysv ipc locking scheme: + * rcu_read_lock() + * obtain the ipc object (kern_ipc_perm) by looking up the id in an idr + * tree. + * - perform initial checks (capabilities, auditing and permission, + * etc). + * - perform read-only operations, such as STAT, INFO commands. + * acquire the ipc lock (kern_ipc_perm.lock) through + * ipc_lock_object() + * - perform data updates, such as SET, RMID commands and + * mechanism-specific operations (semop/semtimedop, + * msgsnd/msgrcv, shmat/shmdt). + * drop the ipc lock, through ipc_unlock_object(). + * rcu_read_unlock() + * + * The ids->rwsem must be taken when: + * - creating, removing and iterating the existing entries in ipc + * identifier sets. + * - iterating through files under /proc/sysvipc/ + * + * Note that sems have a special fast path that avoids kern_ipc_perm.lock - + * see sem_lock(). */ #include <linux/mm.h> @@ -119,7 +142,7 @@ __initcall(ipc_init); void ipc_init_ids(struct ipc_ids *ids) { - init_rwsem(&ids->rw_mutex); + init_rwsem(&ids->rwsem); ids->in_use = 0; ids->seq = 0; @@ -174,7 +197,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header, * @ids: Identifier set * @key: The key to find * - * Requires ipc_ids.rw_mutex locked. + * Requires ipc_ids.rwsem locked. * Returns the LOCKED pointer to the ipc structure if found or NULL * if not. * If key is found ipc points to the owning ipc structure @@ -197,7 +220,8 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key) continue; } - ipc_lock_by_ptr(ipc); + rcu_read_lock(); + ipc_lock_object(ipc); return ipc; } @@ -208,7 +232,7 @@ static struct kern_ipc_perm *ipc_findkey(struct ipc_ids *ids, key_t key) * ipc_get_maxid - get the last assigned id * @ids: IPC identifier set * - * Called with ipc_ids.rw_mutex held. + * Called with ipc_ids.rwsem held. */ int ipc_get_maxid(struct ipc_ids *ids) @@ -246,7 +270,7 @@ int ipc_get_maxid(struct ipc_ids *ids) * is returned. The 'new' entry is returned in a locked state on success. * On failure the entry is not locked and a negative err-code is returned. * - * Called with writer ipc_ids.rw_mutex held. + * Called with writer ipc_ids.rwsem held. */ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size) { @@ -312,9 +336,9 @@ static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, { int err; - down_write(&ids->rw_mutex); + down_write(&ids->rwsem); err = ops->getnew(ns, params); - up_write(&ids->rw_mutex); + up_write(&ids->rwsem); return err; } @@ -331,7 +355,7 @@ static int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, * * On success, the IPC id is returned. * - * It is called with ipc_ids.rw_mutex and ipcp->lock held. + * It is called with ipc_ids.rwsem and ipcp->lock held. */ static int ipc_check_perms(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp, @@ -376,7 +400,7 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, * Take the lock as a writer since we are potentially going to add * a new entry + read locks are not "upgradable" */ - down_write(&ids->rw_mutex); + down_write(&ids->rwsem); ipcp = ipc_findkey(ids, params->key); if (ipcp == NULL) { /* key not used */ @@ -402,7 +426,7 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, } ipc_unlock(ipcp); } - up_write(&ids->rw_mutex); + up_write(&ids->rwsem); return err; } @@ -413,7 +437,7 @@ static int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, * @ids: IPC identifier set * @ipcp: ipc perm structure containing the identifier to remove * - * ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held + * ipc_ids.rwsem (as a writer) and the spinlock for this ID are held * before this function is called, and remain locked on the exit. */ @@ -465,11 +489,6 @@ void ipc_free(void* ptr, int size) kfree(ptr); } -struct ipc_rcu { - struct rcu_head rcu; - atomic_t refcount; -} ____cacheline_aligned_in_smp; - /** * ipc_rcu_alloc - allocate ipc and rcu space * @size: size desired @@ -496,27 +515,24 @@ int ipc_rcu_getref(void *ptr) return atomic_inc_not_zero(&p->refcount); } -/** - * ipc_schedule_free - free ipc + rcu space - * @head: RCU callback structure for queued work - */ -static void ipc_schedule_free(struct rcu_head *head) -{ - vfree(container_of(head, struct ipc_rcu, rcu)); -} - -void ipc_rcu_putref(void *ptr) +void ipc_rcu_putref(void *ptr, void (*func)(struct rcu_head *head)) { struct ipc_rcu *p = ((struct ipc_rcu *)ptr) - 1; if (!atomic_dec_and_test(&p->refcount)) return; - if (is_vmalloc_addr(ptr)) { - call_rcu(&p->rcu, ipc_schedule_free); - } else { - kfree_rcu(p, rcu); - } + call_rcu(&p->rcu, func); +} + +void ipc_rcu_free(struct rcu_head *head) +{ + struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu); + + if (is_vmalloc_addr(p)) + vfree(p); + else + kfree(p); } /** @@ -621,7 +637,7 @@ struct kern_ipc_perm *ipc_obtain_object(struct ipc_ids *ids, int id) } /** - * ipc_lock - Lock an ipc structure without rw_mutex held + * ipc_lock - Lock an ipc structure without rwsem held * @ids: IPC identifier set * @id: ipc id to look for * @@ -677,22 +693,6 @@ out: return out; } -struct kern_ipc_perm *ipc_lock_check(struct ipc_ids *ids, int id) -{ - struct kern_ipc_perm *out; - - out = ipc_lock(ids, id); - if (IS_ERR(out)) - return out; - - if (ipc_checkid(out, id)) { - ipc_unlock(out); - return ERR_PTR(-EIDRM); - } - - return out; -} - /** * ipcget - Common sys_*get() code * @ns : namsepace @@ -733,7 +733,7 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out) } /** - * ipcctl_pre_down - retrieve an ipc and check permissions for some IPC_XXX cmd + * ipcctl_pre_down_nolock - retrieve an ipc and check permissions for some IPC_XXX cmd * @ns: the ipc namespace * @ids: the table of ids where to look for the ipc * @id: the id of the ipc to retrieve @@ -746,29 +746,13 @@ int ipc_update_perm(struct ipc64_perm *in, struct kern_ipc_perm *out) * It must be called without any lock held and * - retrieves the ipc with the given id in the given table. * - performs some audit and permission check, depending on the given cmd - * - returns the ipc with the ipc lock held in case of success - * or an err-code without any lock held otherwise. + * - returns a pointer to the ipc object or otherwise, the corresponding error. * - * Call holding the both the rw_mutex and the rcu read lock. + * Call holding the both the rwsem and the rcu read lock. */ -struct kern_ipc_perm *ipcctl_pre_down(struct ipc_namespace *ns, - struct ipc_ids *ids, int id, int cmd, - struct ipc64_perm *perm, int extra_perm) -{ - struct kern_ipc_perm *ipcp; - - ipcp = ipcctl_pre_down_nolock(ns, ids, id, cmd, perm, extra_perm); - if (IS_ERR(ipcp)) - goto out; - - spin_lock(&ipcp->lock); -out: - return ipcp; -} - struct kern_ipc_perm *ipcctl_pre_down_nolock(struct ipc_namespace *ns, - struct ipc_ids *ids, int id, int cmd, - struct ipc64_perm *perm, int extra_perm) + struct ipc_ids *ids, int id, int cmd, + struct ipc64_perm *perm, int extra_perm) { kuid_t euid; int err = -EPERM; @@ -846,7 +830,8 @@ static struct kern_ipc_perm *sysvipc_find_ipc(struct ipc_ids *ids, loff_t pos, ipc = idr_find(&ids->ipcs_idr, pos); if (ipc != NULL) { *new_pos = pos + 1; - ipc_lock_by_ptr(ipc); + rcu_read_lock(); + ipc_lock_object(ipc); return ipc; } } @@ -884,7 +869,7 @@ static void *sysvipc_proc_start(struct seq_file *s, loff_t *pos) * Take the lock - this will be released by the corresponding * call to stop(). */ - down_read(&ids->rw_mutex); + down_read(&ids->rwsem); /* pos < 0 is invalid */ if (*pos < 0) @@ -911,7 +896,7 @@ static void sysvipc_proc_stop(struct seq_file *s, void *it) ids = &iter->ns->ids[iface->ids]; /* Release the lock we took in start() */ - up_read(&ids->rw_mutex); + up_read(&ids->rwsem); } static int sysvipc_proc_show(struct seq_file *s, void *it) |