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From:   SeongJae Park <sj@kernel.org>
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     Xin Hao <xhao@linux.alibaba.com>, sj@kernel.org,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND MERGE REQUEST] mm/damon: move damon_rand() definition into damon.h
Date:   Fri,  3 Dec 2021 09:19:36 +0000
Message-Id: <20211203091936.19804-1-sj@kernel.org>
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On Thu, 2 Dec 2021 15:12:13 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:

> On Thu,  2 Dec 2021 15:58:59 +0800 Xin Hao <xhao@linux.alibaba.com> wrote:
> 
> > damon_rand() is called in three files:damon/core.c, damon/
> > paddr.c, damon/vaddr.c, i think there is no need to redefine
> > this twice, So move it to damon.h will be a good choice.
> 
> Fair enough.
> 
> > +/* Get a random number in [l, r) */
> > +#define damon_rand(l, r) (l + prandom_u32_max(r - l))
> 
> This shouldn't be implemented as a macro, for all the usual reasons
> (typechecking, side-effects, ugliness, code-documentation site, etc).

Yes, agreed.

> 
> In particular, this expression references `l' twice, so calling
> 
> 	damon_rand(a++, b);
> 
> will increment `a' twice, surprise surprise.

Thank you for this nice explanation.

> 
> Can someone please send a followup patch to convert this (and any
> similar damon macros) into (probably static inlined) C functions?

Sure, I will do, unless someone shows interest here.


Thanks,
SJ