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authorRik van Riel <riel@surriel.com>2013-04-30 19:15:35 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-01 08:12:58 -0700
commitc460b662d5cae467f1c341c59b02a5c5e68fed0b (patch)
tree0cc2f44f5a0abd0a7a143d8bd57630e27bc52311 /ipc
parent16df3674efe39f3ab63e7052f1244dd3d50e7f84 (diff)
downloadlinux-c460b662d5cae467f1c341c59b02a5c5e68fed0b.tar.gz
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')
-rw-r--r--ipc/sem.c29
1 files changed, 23 insertions, 6 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index cd1093cf7e8..70020066ac0 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.