From c460b662d5cae467f1c341c59b02a5c5e68fed0b Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Tue, 30 Apr 2013 19:15:35 -0700 Subject: [PATCH] ipc,sem: open code and rename sem_lock Rename sem_lock() to sem_obtain_lock(), so we can introduce a sem_lock() later that only locks the sem_array and does nothing else. Open code the locking from ipc_lock() in sem_obtain_lock() so we can introduce finer grained locking for the sem_array in the next patch. [akpm@linux-foundation.org: propagate the ipc_obtain_object() errno out of sem_obtain_lock()] Signed-off-by: Rik van Riel Acked-by: Davidlohr Bueso Cc: Chegu Vinod Cc: Emmanuel Benisty Cc: Jason Low Cc: Michel Lespinasse Cc: Peter Hurley Cc: Stanislav Kinsbursky Tested-by: Sedat Dilek Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- ipc/sem.c | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index cd1093c..7002006 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -194,14 +194,31 @@ void __init sem_init (void) * sem_lock_(check_) routines are called in the paths where the rw_mutex * is not held. */ -static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id) +static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns, int id) { - struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id); + struct kern_ipc_perm *ipcp; + struct sem_array *sma; - if (IS_ERR(ipcp)) - return (struct sem_array *)ipcp; + rcu_read_lock(); + ipcp = ipc_obtain_object(&sem_ids(ns), id); + if (IS_ERR(ipcp)) { + sma = ERR_CAST(ipcp); + goto err; + } - return container_of(ipcp, struct sem_array, sem_perm); + spin_lock(&ipcp->lock); + + /* ipc_rmid() may have already freed the ID while sem_lock + * was spinning: verify that the structure is still valid + */ + if (!ipcp->deleted) + return container_of(ipcp, struct sem_array, sem_perm); + + spin_unlock(&ipcp->lock); + sma = ERR_PTR(-EINVAL); +err: + rcu_read_unlock(); + return sma; } static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) @@ -1593,7 +1610,7 @@ sleep_again: goto out_free; } - sma = sem_lock(ns, semid); + sma = sem_obtain_lock(ns, semid); /* * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing. -- 2.7.4