linux-kernel - Re: [PATCHv2 0/4] tools/memory-model: Define more of LKMM in tools/memory-model

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Message-ID: <76bc2c08-655c-4ca4-a573-16a98b7dd919@huaweicloud.com>
Date: Mon, 29 Jul 2024 18:05:36 +0200
From: Jonas Oberhauser <jonas.oberhauser@...weicloud.com>
To: Hernan Ponce de Leon <hernan.poncedeleon@...weicloud.com>,
 Alan Stern <stern@...land.harvard.edu>
Cc: paulmck@...nel.org, parri.andrea@...il.com, will@...nel.org,
 peterz@...radead.org, boqun.feng@...il.com, npiggin@...il.com,
 dhowells@...hat.com, j.alglave@....ac.uk, luc.maranget@...ia.fr,
 akiyks@...il.com, dlustig@...dia.com, joel@...lfernandes.org,
 urezki@...il.com, quic_neeraju@...cinc.com, frederic@...nel.org,
 linux-kernel@...r.kernel.org, lkmm@...ts.linux.dev
Subject: Re: [PATCHv2 0/4] tools/memory-model: Define more of LKMM in
 tools/memory-model



Am 7/29/2024 um 5:53 PM schrieb Hernan Ponce de Leon:
> On 7/29/2024 5:44 PM, Jonas Oberhauser wrote:
>>
>>
>> I don't think this is a problem. If the old version is the default, 
>> and we define it in the .cfg file for the tree version of LKMM, then 
>> it will work correctly for both the old and new versions. People 
>> playing around with Memory Models should be careful enough not to 
>> intentionally break the model by passing bogus options.
> 
> The same was true for my implementation using the lkmm-legacy option

Yeah, I'm fine with that one. (Although it may be better to have a 
version number as value instead of just a boolean flag, like 
-model-version=x_y_z - just in case this is not the last time).

> rather than the model variant, but this was still considered to break 
> backward compatibility.
> 
> https://github.com/herd/herdtools7/pull/865#issuecomment-2229930493

I think Akira is a bit overzealous here. What if a user accidentally 
puts -lkmm-legacy false and accidentally also adds the version number 
into the litmus test and/or model?

The request can be fulfilled, by defining some relation in the bell file 
that has a magic name like version_x_y_z and checks that the x_y_z 
matches the -model-version=x_y_z provided as an argument.

But I don't think we need to go that far.

jonas