linux-kernel - Re: [PATCH 2/3] Fix: tracepoint: static call function vs data state mismatch (v2)

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Message-ID: <20210805153817.1c82dcc6@oasis.local.home>
Date:   Thu, 5 Aug 2021 15:38:17 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        paulmck <paulmck@...nel.org>,
        Stefan Metzmacher <metze@...ba.org>,
        stable <stable@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] Fix: tracepoint: static call function vs data state
 mismatch (v2)

On Thu, 5 Aug 2021 15:15:43 -0400 (EDT)
Mathieu Desnoyers <mathieu.desnoyers@...icios.com> wrote:

> ----- On Aug 5, 2021, at 2:56 PM, rostedt rostedt@...dmis.org wrote:
> 
> > Note, there shouldn't be a "(v2)" outside the "[PATCH ]" part.
> > Otherwise it gets added into the git commit during "git am".  
> 
> Out of curiosity, do you know any way to annotate my local commits to have the
> [PATCH v2] tag automatically generated by git send-email ?

I pass -v2 to git send-email, and it adds the v2 for me.

> > This is a big enough regression, I'll even add a Fixes tag to the next
> > patch on the final sha1 of this patch! Such that this patch won't be
> > backported without the next patch.  
> 
> This makes sense. I still wanted to keep the two patches separate so we would
> introduce the (slow) state machine in the first patch, and optimize for
> speed in the second. My intent is to facilitate of small logical changes,
> and make bisection more precise in the future if we introduce an issue
> here.

I agree which is why I didn't ask you to fold them. The logic in this
code was a big enough change, where I agree it should be kept separate.
Unfortunately, it caused a huge performance regression :-(, but at the
same time, fixed a correctness issue, which Thomas always says that
correctness trumps performance.

But the compromise is to add a Fixes tag to the next patch and document
why they are separated, but still required to act as "one". I'll add
that commentary.

-- Steve

> 
> Calling out more clearly how slow things become with this patch is indeed
> important.
> 
> >   
> >> 
>