linux-kernel - Re: [PATCH 1/5] ipc/sem: do not call wake_sem_queue

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Date:   Tue, 13 Sep 2016 01:14:41 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Manfred Spraul <manfred@...orfullife.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 1/5] ipc/sem: do not call wake_sem_queue_do() prematurely

On Tue, 13 Sep 2016, Manfred Spraul wrote:

>>-	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
>>-		goto out_rcu_wakeup;
>>+	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
>>+		rcu_read_unlock();
>>+		goto out_free;
>>+	}
>Is this really better/simpler?
>You replace "if (error) goto cleanup" with "if (error) {cleanup_1(); 
>goto cleanup_2()}".

I believe it is better as it clearly separates blocking from non-blocking
exit paths. Overhead of course is irrelevant in both in-house wake_up_sem_queue_do
and wake_up_q.

Thanks,
Davidlohr