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Subject[PATCH v2 6/4] ipc: open code and rename sem_lock
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 efb49e7..d92ba32 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;
+
+ write_lock(&ipcp->lock);
+
+ /* ipc_rmid() may have already freed the ID while write_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:
+ write_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)
@@ -1558,7 +1573,7 @@ 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.


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