linux-kernel - Re: [PATCH 2/3] locking/percpu-rwsem: Replace bulky wait-queues with swait

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Message-ID: <20161121172647.GB31288@linux-80c1.suse>
Date:   Mon, 21 Nov 2016 09:26:47 -0800
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     mingo@...nel.org, peterz@...radead.org, john.stultz@...aro.org,
        dimitrysh@...gle.com, linux-kernel@...r.kernel.org,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH 2/3] locking/percpu-rwsem: Replace bulky wait-queues with
 swait

On Mon, 21 Nov 2016, Oleg Nesterov wrote:

>On 11/18, Davidlohr Bueso wrote:
>>
>> @@ -12,7 +12,7 @@ struct percpu_rw_semaphore {
>>  	struct rcu_sync		rss;
>>  	unsigned int __percpu	*read_count;
>>  	struct rw_semaphore	rw_sem;
>> -	wait_queue_head_t	writer;
>> +	struct swait_queue_head	writer;
>
>I won't argue, but even swait_queue_head is overkill in this case.
>
>We can just add "struct task_struct *writer" into percpu_rw_semaphore,

Given that this is how all things locking/ work, I very much agree with
you, lemme send a v2.