sysvipc: duplicate lock comments wrt ipc_addid()

The comment in msgqueues when using ipc_addid() is quite useful imo.
Duplicate it for shm and semaphores.

Link: http://lkml.kernel.org/r/20170831172049.14576-3-dave@stgolabs.net
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 2 insertions, 0 deletions

diff --git a/ipc/sem.c b/ipc/sem.c
index b2698ebdcb31..28a5c9f0be87 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -515,6 +515,7 @@ static int newary(struct ipc_namespace *ns, struct ipc_params *params)
         sma->sem_nsems = nsems;
         sma->sem_ctime = ktime_get_real_seconds();
 
+        /* ipc_addid() locks sma upon success. */
         retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
         if (retval < 0) {
                 call_rcu(&sma->sem_perm.rcu, sem_rcu_free);
diff --git a/ipc/shm.c b/ipc/shm.c
index bd652755d32c..378c929194ce 100644
--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -601,6 +601,7 @@ static int newseg(struct ipc_namespace *ns, struct ipc_params *params)
         shp->shm_file = file;
         shp->shm_creator = current;
 
+        /* ipc_addid() locks shp upon success. */
         error = ipc_addid(&shm_ids(ns), &shp->shm_perm, ns->shm_ctlmni);
         if (error < 0)
                 goto no_id;