The patch titled
Subject: ipc,sem: open code and rename sem_lock
has been added to the -mm tree. Its filename is
ipcsem-open-code-and-rename-sem_lock.patch
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From: Rik van Riel <riel@xxxxxxxxxxx>
Subject: 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 <riel@xxxxxxxxxx>
Acked-by: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Cc: Chegu Vinod <chegu_vinod@xxxxxx>
Cc: Emmanuel Benisty <benisty.e@xxxxxxxxx>
Cc: Jason Low <jason.low2@xxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Cc: Stanislav Kinsbursky <skinsbursky@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)
diff -puN ipc/sem.c~ipcsem-open-code-and-rename-sem_lock ipc/sem.c
--- a/ipc/sem.c~ipcsem-open-code-and-rename-sem_lock
+++ a/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.
_
Patches currently in -mm which might be from riel@xxxxxxxxxxx are
ipcsem-open-code-and-rename-sem_lock.patch
ipcsem-open-code-and-rename-sem_lock-fix.patch
ipcsem-have-only-one-list-in-struct-sem_queue.patch
ipcsem-fine-grained-locking-for-semtimedop.patch
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