linux-kernel - Re: [QUESTION] llist: Comment releasing 'must delete' restriction before traversing

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Date:   Tue, 31 Jul 2018 14:25:51 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     linux-kernel@...r.kernel.org, kernel-team@....com,
        peterz@...radead.org, mingo@...nel.org, jiangshanlai@...il.com,
        paulmck@...ux.vnet.ibm.com, josh@...htriplett.org,
        rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        joel@...lfernandes.org, len.brown@...el.com, glider@...gle.com,
        peter@...leysoftware.com, aik@...abs.ru
Subject: Re: [QUESTION] llist: Comment releasing 'must delete' restriction
 before traversing

On Tue, Jul 31, 2018 at 09:37:50AM +0800, Huang, Ying wrote:
> Byungchul Park <byungchul.park@....com> writes:
> 
> > Hello folks,
> >
> > I'm careful in saying.. and curious about..
> >
> > In restrictive cases like only addtions happen but never deletion, can't
> > we safely traverse a llist? I believe llist can be more useful if we can
> > release the restriction. Can't we?
> >
> > If yes, we may add another function traversing starting from a head. Or
> > just use existing funtion with head->first.
> >
> > Thank a lot for your answers in advance :)
> 
> What's the use case?  I don't know how it is useful that items are never
> deleted from the llist.
> 
> Some other locks could be used to provide mutual exclusive between
> 
> - llist add, llist traverse

Hello Huang,

In my use case, I only do adding and traversing on a llist.

> 
> and
> 
> - llist delete

Of course, I will use a lock when deletion is needed.

So.. in the case only adding into and traversing a llist is needed,
can't we safely traverse a llist in the way I thought? Or am I missing
something?

Thank you.

> Is this your use case?
> 
> Best Regards,
> Huang, Ying