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Message-ID: <Y1o2k+2PTMJ2X9QA@kadam>
Date: Thu, 27 Oct 2022 10:43:15 +0300
From: Dan Carpenter <dan.carpenter@...cle.com>
To: Liam Howlett <liam.howlett@...cle.com>
Cc: Lukas Bulwahn <lukas.bulwahn@...il.com>,
Matthew Wilcox <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>
Subject: Re: [PATCH 0/1] Dead stores in maple-tree
On Wed, Oct 26, 2022 at 02:23:19PM +0000, Liam Howlett wrote:
> * Lukas Bulwahn <lukas.bulwahn@...il.com> [221026 08:01]:
> > Dear maple-tree authors, dear Liam, dear Matthew,
> >
> > there are some Dead Stores that clang-analyzer reports:
> >
> > lib/maple_tree.c:2906:2: warning: Value stored to 'last' is never read [clang-analyzer-deadcode.DeadStores]
> > lib/maple_tree.c:2907:2: warning: Value stored to 'prev_min' is never read [clang-analyzer-deadcode.DeadStores]
> >
> > I addressed these two cases, which were most obvious and clear to fix;
> > see patch of this one-element series.
> >
> > Further, clang-analyzer reports more, which I did not address:
> >
> > lib/maple_tree.c:332:2: warning: Value stored to 'node' is never read [clang-analyzer-deadcode.DeadStores]
> > lib/maple_tree.c:337:2: warning: Value stored to 'node' is never read [clang-analyzer-deadcode.DeadStores]
> >
> > Unclear to me if the tool is wrong or right in its analysis here for the two functions above.
>
> The tool is correct but these aren't going anywhere. They are compiled
> out and are needed for the future.
>
lib/maple_tree.c
330 static inline void mte_set_full(const struct maple_enode *node)
331 {
332 node = (void *)((unsigned long)node & ~MAPLE_ENODE_NULL);
333 }
334
335 static inline void mte_clear_full(const struct maple_enode *node)
336 {
337 node = (void *)((unsigned long)node | MAPLE_ENODE_NULL);
338 }
That code is really puzzling... How far into the future before it starts
making sense?
regards,
dan carpenter
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