Messages in this thread Patch in this message | | | From | Rik van Riel <> | Subject | [PATCH 5/7] ipc,sem: open code and rename sem_lock | Date | Wed, 20 Mar 2013 15:55:35 -0400 |
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Rename sem_lock to sem_obtain_lock, so we can introduce a sem_lock function 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 <riel@redhat.com> --- ipc/sem.c | 23 +++++++++++++++++++---- 1 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/ipc/sem.c b/ipc/sem.c index ff3d4ff..d25f9b6 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) @@ -1562,7 +1577,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, 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. -- 1.7.7.6
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