X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=ipc%2Futil.c;h=1aa0ebf71bac7e5c30559eb0f60a89bdc6688efb;hb=3ba5619f06300cd0944150901ed20de87483ad8c;hp=fd29246dc3c8ae1b6869f7ec3a8787c98d042ae2;hpb=f4566f04854d78acfc74b9acb029744acde9d033;p=linux-2.6 diff --git a/ipc/util.c b/ipc/util.c index fd29246dc3..1aa0ebf71b 100644 --- a/ipc/util.c +++ b/ipc/util.c @@ -32,6 +32,7 @@ #include #include #include +#include #include @@ -136,7 +137,7 @@ __initcall(ipc_init); void ipc_init_ids(struct ipc_ids *ids) { - mutex_init(&ids->mutex); + init_rwsem(&ids->rw_mutex); ids->in_use = 0; ids->seq = 0; @@ -191,7 +192,7 @@ void __init ipc_init_proc_interface(const char *path, const char *header, * @ids: Identifier set * @key: The key to find * - * Requires ipc_ids.mutex locked. + * Requires ipc_ids.rw_mutex 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 @@ -225,7 +226,7 @@ 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.mutex held. + * Called with ipc_ids.rw_mutex held. */ int ipc_get_maxid(struct ipc_ids *ids) @@ -261,9 +262,9 @@ int ipc_get_maxid(struct ipc_ids *ids) * Add an entry 'new' to the IPC ids idr. The permissions object is * initialised and the first free entry is set up and the id assigned * is returned. The 'new' entry is returned in a locked state on success. - * On failure the entry is not locked and -1 is returned. + * On failure the entry is not locked and a negative err-code is returned. * - * Called with ipc_ids.mutex held. + * Called with ipc_ids.rw_mutex held as a writer. */ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size) @@ -274,11 +275,11 @@ int ipc_addid(struct ipc_ids* ids, struct kern_ipc_perm* new, int size) size = IPCMNI; if (ids->in_use >= size) - return -1; + return -ENOSPC; err = idr_get_new(&ids->ipcs_idr, new, &id); if (err) - return -1; + return err; ids->in_use++; @@ -310,15 +311,18 @@ int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, struct ipc_ops *ops, struct ipc_params *params) { int err; - +retry: err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL); if (!err) return -ENOMEM; - mutex_lock(&ids->mutex); + down_write(&ids->rw_mutex); err = ops->getnew(ns, params); - mutex_unlock(&ids->mutex); + up_write(&ids->rw_mutex); + + if (err == -EAGAIN) + goto retry; return err; } @@ -335,7 +339,7 @@ int ipcget_new(struct ipc_namespace *ns, struct ipc_ids *ids, * * On success, the IPC id is returned. * - * It is called with ipc_ids.mutex and ipcp->lock held. + * It is called with ipc_ids.rw_mutex and ipcp->lock held. */ static int ipc_check_perms(struct kern_ipc_perm *ipcp, struct ipc_ops *ops, struct ipc_params *params) @@ -373,10 +377,14 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, struct kern_ipc_perm *ipcp; int flg = params->flg; int err; - +retry: err = idr_pre_get(&ids->ipcs_idr, GFP_KERNEL); - mutex_lock(&ids->mutex); + /* + * 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); ipcp = ipc_findkey(ids, params->key); if (ipcp == NULL) { /* key not used */ @@ -404,7 +412,10 @@ int ipcget_public(struct ipc_namespace *ns, struct ipc_ids *ids, } ipc_unlock(ipcp); } - mutex_unlock(&ids->mutex); + up_write(&ids->rw_mutex); + + if (err == -EAGAIN) + goto retry; return err; } @@ -415,8 +426,8 @@ 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.mutex and the spinlock for this ID are held before this - * function is called, and remain locked on the exit. + * ipc_ids.rw_mutex (as a writer) and the spinlock for this ID are held + * before this function is called, and remain locked on the exit. */ void ipc_rmid(struct ipc_ids *ids, struct kern_ipc_perm *ipcp) @@ -680,15 +691,17 @@ void ipc64_perm_to_ipc_perm (struct ipc64_perm *in, struct ipc_perm *out) } /** - * ipc_lock - Lock an ipc structure + * ipc_lock - Lock an ipc structure without rw_mutex held * @ids: IPC identifier set * @id: ipc id to look for * * Look for an id in the ipc ids idr and lock the associated ipc object. * - * ipc_ids.mutex is not necessarily held before this function is called, - * that's why we enter a RCU read section. * The ipc object is locked on exit. + * + * This is the routine that should be called when the rw_mutex is not already + * held, i.e. idr tree not protected: it protects the idr tree in read mode + * during the idr_find(). */ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) @@ -696,13 +709,18 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) struct kern_ipc_perm *out; int lid = ipcid_to_idx(id); + down_read(&ids->rw_mutex); + rcu_read_lock(); out = idr_find(&ids->ipcs_idr, lid); if (out == NULL) { rcu_read_unlock(); + up_read(&ids->rw_mutex); return ERR_PTR(-EINVAL); } + up_read(&ids->rw_mutex); + spin_lock(&out->lock); /* ipc_rmid() may have already freed the ID while ipc_lock @@ -717,6 +735,40 @@ struct kern_ipc_perm *ipc_lock(struct ipc_ids *ids, int id) return out; } +/** + * ipc_lock_down - Lock an ipc structure with rw_sem held + * @ids: IPC identifier set + * @id: ipc id to look for + * + * Look for an id in the ipc ids idr and lock the associated ipc object. + * + * The ipc object is locked on exit. + * + * This is the routine that should be called when the rw_mutex is already + * held, i.e. idr tree protected. + */ + +struct kern_ipc_perm *ipc_lock_down(struct ipc_ids *ids, int id) +{ + struct kern_ipc_perm *out; + int lid = ipcid_to_idx(id); + + rcu_read_lock(); + out = idr_find(&ids->ipcs_idr, lid); + if (out == NULL) { + rcu_read_unlock(); + return ERR_PTR(-EINVAL); + } + + spin_lock(&out->lock); + + /* + * No need to verify that the structure is still valid since the + * rw_mutex is held. + */ + return out; +} + #ifdef __ARCH_WANT_IPC_PARSE_VERSION @@ -808,7 +860,7 @@ 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(). */ - mutex_lock(&ids->mutex); + down_read(&ids->rw_mutex); /* pos < 0 is invalid */ if (*pos < 0) @@ -835,7 +887,7 @@ static void sysvipc_proc_stop(struct seq_file *s, void *it) ids = iter->ns->ids[iface->ids]; /* Release the lock we took in start() */ - mutex_unlock(&ids->mutex); + up_read(&ids->rw_mutex); } static int sysvipc_proc_show(struct seq_file *s, void *it)