path: root/ipc
diff options
authorManfred Spraul <manfred@colorfullife.com>2014-06-06 14:37:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-06 16:08:15 -0700
commit9b44ee2eef124885d407a5f59bbd7a72634a05ba (patch)
treedac074013457836c44164039bab63d6cc8b32018 /ipc
parentb220c57aeccf903ec6550b30c52cc0248ddb26bf (diff)
ipc/sem.c: add a printk_once for semctl(GETNCNT/GETZCNT)
The actual Linux implementation for semctl(GETNCNT) and semctl(GETZCNT) always (since 0.99.10) reported a thread as sleeping on all semaphores that are listed in the semop() call. The documented behavior (both in the Linux man page and in the Single Unix Specification) is that a task should be reported on exactly one semaphore: The semaphore that caused the thread to got to sleep. This patch adds a pr_info_once() that is triggered if a thread hits the relevant case. The code triggers slightly too often, otherwise it would be necessary to replicate the old code. As there are no known users of GETNCNT or GETZCNT, this is done to prevent unnecessary bloat. The task that triggered is reported with name (tsk->comm) and pid. Signed-off-by: Manfred Spraul <manfred@colorfullife.com> Acked-by: Davidlohr Bueso <davidlohr@hp.com> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Joe Perches <joe@perches.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'ipc')
1 files changed, 11 insertions, 0 deletions
diff --git a/ipc/sem.c b/ipc/sem.c
index 910c7a3865c8..454f6c6020a8 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1000,6 +1000,17 @@ static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
struct sembuf *sop = q->blocking;
+ /*
+ * Linux always (since 0.99.10) reported a task as sleeping on all
+ * semaphores. This violates SUS, therefore it was changed to the
+ * standard compliant behavior.
+ * Give the administrators a chance to notice that an application
+ * might misbehave because it relies on the Linux behavior.
+ */
+ pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
+ "The task %s (%d) triggered the difference, watch for misbehavior.\n",
+ current->comm, task_pid_nr(current));
if (sop->sem_num != semnum)
return 0;

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