From e1eeb422b39505438346587b8a7660082dcb6f11 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Wed, 27 Mar 2013 10:26:02 +1100 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. Signed-off-by: Rik van Riel Acked-by: Davidlohr Bueso Cc: Chegu Vinod Cc: Emmanuel Benisty Cc: Jason Low Cc: Linus Torvalds Cc: Michel Lespinasse Cc: Peter Hurley Cc: Stanislav Kinsbursky Signed-off-by: Andrew Morton --- ipc/sem.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/ipc/sem.c b/ipc/sem.c index 2c57e2143c0e..26c39ec01ab7 100644 --- a/ipc/sem.c +++ b/ipc/sem.c @@ -194,14 +194,29 @@ 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; + rcu_read_lock(); + ipcp = ipc_obtain_object(&sem_ids(ns), id); if (IS_ERR(ipcp)) - return (struct sem_array *)ipcp; + goto err1; + + 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) + goto err0; return container_of(ipcp, struct sem_array, sem_perm); +err0: + spin_unlock(&ipcp->lock); +err1: + rcu_read_unlock(); + return ERR_PTR(-EINVAL); } static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) @@ -1591,7 +1606,7 @@ 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. -- 2.39.5