include/linux/sem.h: correctly document sem_ctime

sem_ctime is initialized to the semget() time and then updated at every
semctl() that changes the array.

Thus it does not represent the time of the last change.

Especially, semop() calls are only stored in sem_otime, not in
sem_ctime.

This is already described in ipc/sem.c, I just overlooked that there is
a comment in include/linux/sem.h and man semctl(2) as well.

So: Correct wrong comments.

Link: http://lkml.kernel.org/r/20170515171912.6298-4-manfred@colorfullife.com
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: <1vier1@web.de>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/sem.h b/include/linux/sem.h
index 9db1409..be5cf2e 100644 (file)
--- a/include/linux/sem.h
+++ b/include/linux/sem.h
@@ -30,7 +30,7 @@ struct sem {
 /* One sem_array data structure for each set of semaphores in the system. */
 struct sem_array {
        struct kern_ipc_perm    sem_perm;       /* permissions .. see ipc.h */
-       time_t                  sem_ctime;      /* last change time */
+       time_t                  sem_ctime;      /* create/last semctl() time */
        struct list_head        pending_alter;  /* pending operations */
                                                /* that alter the array */
        struct list_head        pending_const;  /* pending complex operations */

diff --git a/include/uapi/linux/sem.h b/include/uapi/linux/sem.h
index dd73b90..67eb903 100644 (file)
--- a/include/uapi/linux/sem.h
+++ b/include/uapi/linux/sem.h
@@ -23,7 +23,7 @@
 struct semid_ds {
        struct ipc_perm sem_perm;               /* permissions .. see ipc.h */
        __kernel_time_t sem_otime;              /* last semop time */
-       __kernel_time_t sem_ctime;              /* last change time */
+       __kernel_time_t sem_ctime;              /* create/last semctl() time */
        struct sem      *sem_base;              /* ptr to first semaphore in array */
        struct sem_queue *sem_pending;          /* pending operations to be processed */
        struct sem_queue **sem_pending_last;    /* last pending operation */