diff options
Diffstat (limited to 'ipc/shm.c')
| -rw-r--r-- | ipc/shm.c | 39 |
1 files changed, 26 insertions, 13 deletions
diff --git a/ipc/shm.c b/ipc/shm.c index e2de16efe10..f28f2a3163e 100644 --- a/ipc/shm.c +++ b/ipc/shm.c @@ -82,6 +82,10 @@ static void __shm_init_ns(struct ipc_namespace *ns, struct ipc_ids *ids) ipc_init_ids(ids); } +/* + * Called with shm_ids.mutex and the shp structure locked. + * Only shm_ids.mutex remains locked on exit. + */ static void do_shm_rmid(struct ipc_namespace *ns, struct shmid_kernel *shp) { if (shp->shm_nattch){ @@ -182,6 +186,7 @@ static void shm_open(struct vm_area_struct *vma) /* * shm_destroy - free the struct shmid_kernel * + * @ns: namespace * @shp: struct to free * * It has to be called with shp and shm_ids.mutex locked, @@ -343,6 +348,14 @@ static struct vm_operations_struct shm_vm_ops = { #endif }; +/** + * newseg - Create a new shared memory segment + * @ns: namespace + * @params: ptr to the structure that contains key, size and shmflg + * + * Called with shm_ids.mutex held + */ + static int newseg(struct ipc_namespace *ns, struct ipc_params *params) { key_t key = params->key; @@ -428,6 +441,9 @@ no_file: return error; } +/* + * Called with shm_ids.mutex and ipcp locked. + */ static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg) { struct shmid_kernel *shp; @@ -436,6 +452,9 @@ static inline int shm_security(struct kern_ipc_perm *ipcp, int shmflg) return security_shm_associate(shp, shmflg); } +/* + * Called with shm_ids.mutex and ipcp locked. + */ static inline int shm_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params) { @@ -558,6 +577,9 @@ static inline unsigned long copy_shminfo_to_user(void __user *buf, struct shminf } } +/* + * Called with shm_ids.mutex held + */ static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss, unsigned long *swp) { @@ -573,18 +595,6 @@ static void shm_get_stat(struct ipc_namespace *ns, unsigned long *rss, struct shmid_kernel *shp; struct inode *inode; - /* - * idr_find() is called via shm_get(), so with shm_ids.mutex - * locked. Since ipc_addid() is also called with - * shm_ids.mutex down, there is no need to add read barriers - * here to gurantee the writes in ipc_addid() are seen in - * order here (for Alpha). - * However idr_find() itself does not necessary require - * ipc_ids.mutex down. So if idr_find() is used by other - * places without ipc_ids.mutex down, then it needs read - * read memory barriers as ipc_lock() does. - */ - shp = idr_find(&shm_ids(ns).ipcs_idr, next_id); if (shp == NULL) continue; @@ -638,8 +648,11 @@ asmlinkage long sys_shmctl (int shmid, int cmd, struct shmid_ds __user *buf) shminfo.shmmin = SHMMIN; if(copy_shminfo_to_user (buf, &shminfo, version)) return -EFAULT; - /* reading a integer is always atomic */ + + mutex_lock(&shm_ids(ns).mutex); err = ipc_get_maxid(&shm_ids(ns)); + mutex_unlock(&shm_ids(ns).mutex); + if(err<0) err = 0; goto out; |