The patch titled
Subject: ipc/sem: make semctl setting sempid consistent
has been added to the -mm tree. Its filename is
ipc-sem-make-semctl-setting-sempid-consistent.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ipc-sem-make-semctl-setting-sempid-consistent.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ipc-sem-make-semctl-setting-sempid-consistent.patch
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From: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Subject: ipc/sem: make semctl setting sempid consistent
As indicated by bug#112271, Linux sets the sempid value upon semctl, and
not only for semop calls. However, within semctl we only do this for
SETVAL, leaving SETALL without updating the field, and therefore rather
inconsistent behavior when compared to other Unices.
There is really no documentation regarding this and therefore users should
not make assumptions. With this patch, along with updating semctl.2
manpages, this scenario should become less ambiguous As such, set sempid
on SETALL cmd.
Also update some in-code documentation, specifying where the
sempid is set.
Passes ltp and custom testcase where a child (fork) does SETALL
to the set.
Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
Reported-by: Philip Semanchuk <linux_kernel.20.ick@xxxxxxxxxxxxxxx>
Cc: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
Cc: PrasannaKumar Muralidharan <prasannatsmkumar@xxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
Cc: Herton R. Krzesinski <herton@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
ipc/sem.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff -puN ipc/sem.c~ipc-sem-make-semctl-setting-sempid-consistent ipc/sem.c
--- a/ipc/sem.c~ipc-sem-make-semctl-setting-sempid-consistent
+++ a/ipc/sem.c
@@ -92,7 +92,14 @@
/* One semaphore structure for each semaphore in the system. */
struct sem {
int semval; /* current value */
- int sempid; /* pid of last operation */
+ /*
+ * PID of the process that last modified the semaphore. For
+ * Linux, specifically these are:
+ * - semop
+ * - semctl, via SETVAL and SETALL.
+ * - at task exit when performing undo adjustments (see exit_sem).
+ */
+ int sempid;
spinlock_t lock; /* spinlock for fine-grained semtimedop */
struct list_head pending_alter; /* pending single-sop operations */
/* that alter the semaphore */
@@ -1444,8 +1451,10 @@ static int semctl_main(struct ipc_namesp
goto out_unlock;
}
- for (i = 0; i < nsems; i++)
+ for (i = 0; i < nsems; i++) {
sma->sem_base[i].semval = sem_io[i];
+ sma->sem_base[i].sempid = task_tgid_vnr(current);
+ }
ipc_assert_locked_object(&sma->sem_perm);
list_for_each_entry(un, &sma->list_id, list_id) {
_
Patches currently in -mm which might be from dave@xxxxxxxxxxxx are
ipc-sem-make-semctl-setting-sempid-consistent.patch
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