linux-kernel - Re: [PATCH 8/8] fs/aio: Use rcu_work instead of explicit rcu and work item

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Date:   Wed, 21 Mar 2018 10:53:56 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Oleg Nesterov <oleg@...hat.com>
Cc:     torvalds@...ux-foundation.org, jannh@...gle.com,
        paulmck@...ux.vnet.ibm.com, bcrl@...ck.org,
        viro@...iv.linux.org.uk, kent.overstreet@...il.com,
        security@...nel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com
Subject: Re: [PATCH 8/8] fs/aio: Use rcu_work instead of explicit rcu and
 work item

Hello,

On Wed, Mar 21, 2018 at 06:17:43PM +0100, Oleg Nesterov wrote:
> Mostly I am asking because I do not really understand
> "[PATCH 6/8] RCU, workqueue: Implement rcu_work".
> 
> I mean, the code looks simple and correct but why does it play with
> WORK_STRUCT_PENDING_BIT? IOW, I do not see a "good" use-case when 2 or more
> queue_rcu_work()'s can use the same rwork and hit work_pending() == T. And
> what the caller should do if queue_rcu_work() returns false?

It's just following standard workqueue conventions.  We can try to
make it more specialized but then flush_rcu_work()'s behavior would
have to different too and it gets confusing quickly.  Unless there are
overriding reasons to deviate, I'd like to keep it consistent.

Thanks.

-- 
tejun