diff options
| author | Rik van Riel <riel@surriel.com> | 2013-04-30 19:15:35 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-05-01 08:12:58 -0700 |
| commit | c460b662d5cae467f1c341c59b02a5c5e68fed0b (patch) | |
| tree | 0cc2f44f5a0abd0a7a143d8bd57630e27bc52311 /ipc/sem.c | |
| parent | 16df3674efe39f3ab63e7052f1244dd3d50e7f84 (diff) | |
| download | lwn-c460b662d5cae467f1c341c59b02a5c5e68fed0b.tar.gz lwn-c460b662d5cae467f1c341c59b02a5c5e68fed0b.zip | |
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 <riel@redhat.com>
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Chegu Vinod <chegu_vinod@hp.com>
Cc: Emmanuel Benisty <benisty.e@gmail.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc/sem.c')
| -rw-r--r-- | ipc/sem.c | 29 |
1 files changed, 23 insertions, 6 deletions
diff --git a/ipc/sem.c b/ipc/sem.c index cd1093cf7e8f..70020066ac0d 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. |