linux-kernel - Re: [PATCH 2/3] lockdep: clarify size for LOCKDEP_*

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Message-ID: <ZrJgnP5Nv03k8rMG@boqun-archlinux>
Date: Tue, 6 Aug 2024 10:42:52 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Waiman Long <longman@...hat.com>
Cc: Carlos Llamas <cmllamas@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, kernel-team@...roid.com,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH 2/3] lockdep: clarify size for LOCKDEP_*_BITS configs

On Tue, Aug 06, 2024 at 10:52:52AM -0400, Waiman Long wrote:
> 
> On 8/6/24 10:47, Carlos Llamas wrote:
> > On Mon, Aug 05, 2024 at 09:36:43PM -0400, Waiman Long wrote:
> > > Many kernel developers understand that BITS refers to a size of 2^n. Besides
> > > LOCKDEP, there are also many instances of such use in other kconfig entries.
> > > It can be a bit odd to explicitly state that just for LOCKDEP.
> > > 
> > > Cheers,
> > > Longman
> > Right, and similar to BITS there is SHIFT, which is also a common way to
> > specify the 2^n values. I'd point out though, that it is also common to
> > clarify the "power of two" explicitly. To name a few examples that are
> > doing so: SECURITY_SELINUX_SIDTAB_HASH_BITS, NODES_SHIFT, CMA_ALIGNMENT,
> > IP_VS_SH_TAB_BITS, LOG_BUF_SHIFT but there is more.
> > 
> > Perhaps this is because the audience for these configs is not always a
> > kernel developer?
> > 
> > Anyway, this is pretty much a trivial patch to address Andrew's comment
> > below. But let me know if you think I should drop it, it seems to me it
> > can be helpful.
> > 
> >    [...]
> >    btw, the help text "Bitsize for MAX_LOCKDEP_CHAINS" is odd.  What's a
> >    bitsize?  Maybe "bit shift count for..." or such.
> 
> I am not against this patch. Currently I am neutral. Let's see what Boqun
> think about it.
> 

This looks good to me. Maybe it's a bit verbose but that's what the doc
part should be: providing enough information so more people can be on
the same page. Please keep this one, thanks!

Regards,
Boqun

> Cheers,
> Longman
>