On Sun, 2014-05-25 at 20:21 +0200, Manfred Spraul wrote:
> 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 printk_once() that is triggered if a thread hits
> the relevant case.
[]
> diff --git a/ipc/sem.c b/ipc/sem.c
[]
> @@ -1000,6 +1000,18 @@ 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.
> + */
> + printk_once(KERN_INFO "semctl(GETNCNT/GETZCNT) is since 3.16 Single " \
> + "Unix Specification compliant.\n" \
> + "The task %d triggered the difference, " \
> + "watch for misbehavior.", current->pid);
Unnecessary line continuations.
Missing terminating newline after "misbehavior"
Ideally coalesced or broken at linebreaks like:
pr_info_once("semctl(GETNCNT/GETZCNT) is Single Unix Specification
compliant since kernel v3.16\n"
"Task %d triggered the difference, watch for
misbehavior\n",
current->pid);
> if (sop->sem_num != semnum)
> return 0;
>
Should the printk_once (which could be pr_info_once or _ratelimited
or maybe even emitted at KERN_DEBUG) be done only when
the return is 1?
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