linux-kernel - Re: [PATCH 01/13] seqnum_ops: Introduce Sequence Number Ops

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Date:   Wed, 11 Nov 2020 11:28:13 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     corbet@....net, keescook@...omium.org, gregkh@...uxfoundation.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 01/13] seqnum_ops: Introduce Sequence Number Ops

On 11/11/20 10:50 AM, Peter Zijlstra wrote:
> On Wed, Nov 11, 2020 at 10:34:05AM -0700, Shuah Khan wrote:
> 
>> Not sure what to make of the 6080 atomic_read()s and 3413
>> atomic_inc()s, some of which might be assuming uniqueness
>> guarantee.
> 
> Well, clearly you just did: git grep atimic_{read,inc}() | wc -l and
> didn't look at the usage. Equally clearly there can be bugs. Also
> evidently much of those are not in fact sequence numbers.
> 

Looking at the usage and classifying which usages are sequence
numbers is part of may audit and we are covered. Your explanation
and this discussion helps with do a better audit of these usages.

> All I'm saying is that if you want a sequence number, inc_return (or
> fetch_inc) is the only sane option.
> 

Cool.

thanks,
-- Shuah