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

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Date:   Tue, 31 Jul 2018 13:45:54 +0800
From:   "Huang\, Ying" <ying.huang@...el.com>
To:     Byungchul Park <byungchul.park@....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

Byungchul Park <byungchul.park@....com> writes:

> 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,

Hello Byungchul,

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

Can you provide more details about your use case?

Best Regards,
Huang, Ying

>> 
>> 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