linux-kernel - Re: [PATCH] buffer: Avoid setting buffer bits that are already set

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Message-ID: <131ef377-7edb-738c-4ed1-debac7857434@intel.com>
Date:   Tue, 24 Oct 2017 09:25:44 +0800
From:   kemi <kemi.wang@...el.com>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@...e.cz>,
        Darrick J Wong <darrick.wong@...cle.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        Jeff Layton <jlayton@...hat.com>,
        Dave <dave.hansen@...ux.intel.com>,
        Andi Kleen <andi.kleen@...el.com>,
        Tim Chen <tim.c.chen@...el.com>,
        Ying Huang <ying.huang@...el.com>,
        Aaron Lu <aaron.lu@...el.com>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] buffer: Avoid setting buffer bits that are already set



On 2017年10月24日 09:21, Andi Kleen wrote:
> kemi <kemi.wang@...el.com> writes:
>>
>> I'll see if I can find some
>>> time to implement the above in a nice way.
>>
>> Agree. Maybe something like test_and_set_bit() would be more suitable.
> 
> test_and_set_bit is a very different operation for the CPU because
> it is atomic for both. But we want the initial read to not
> be atomic.
> 

I meant to express the meaning of test before setting bit.
Apologize to make you confused.

> If you add special functions use a different variant that is only
> atomic for the set.
> 
> -Andi
>