linux-kernel - Re: [PATCH] ARM: dove: fix returnvar.cocci warnings

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Message-ID: <CAK8P3a1fjHnLg774-CfSPaWY16PtS56RgsRuEVA8JRrh+ZoY=g@mail.gmail.com>
Date:   Fri, 6 May 2022 09:17:44 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Philip Li <philip.li@...el.com>
Cc:     Dave Hansen <dave.hansen@...el.com>, Arnd Bergmann <arnd@...db.de>,
        kernel test robot <lkp@...el.com>, kbuild-all@...ts.01.org,
        Linux Memory Management List <linux-mm@...ck.org>,
        Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        linux-omap <linux-omap@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: dove: fix returnvar.cocci warnings

On Fri, May 6, 2022 at 3:09 AM Philip Li <philip.li@...el.com> wrote:
> On Thu, May 05, 2022 at 09:31:37AM -0700, Dave Hansen wrote:
> > On 5/3/22 00:21, Arnd Bergmann wrote:
> > > On Tue, May 3, 2022 at 4:45 AM kernel test robot <lkp@...el.com> wrote:
> > >> From: kernel test robot <lkp@...el.com>
> > >>
> > >> arch/arm/mach-omap2/dma.c:82:10-16: Unneeded variable: "errata". Return "0" on line 161
> > >>
> > >>  Remove unneeded variable used to store return value.
> > >>
> > >> Generated by: scripts/coccinelle/misc/returnvar.cocci
> > >>
> > >> Reported-by: kernel test robot <lkp@...el.com>
> > >> Signed-off-by: kernel test robot <lkp@...el.com>
> > > I checked the patch, and unfortunately it is wrong, the current code
> > > needs to stay.
> > > The problem is the SET_DMA_ERRATA() macro that accesses the
> > > local 'errata' variable.
> >
> > 0day folks, do we have humans looking over these before they're going
> > out to the list?  If not, can we add some?  If so, can the humans get a
> > little more discerning? ;)
>
> Sorry all for the bad patch. So far, we pick up several cocci warnings that
> we have confidence based on early result analysis and feedback, for these
> warnings, 0day sends out patch automatically.
>
> Thanks for the suggestion Dave, We will change current process to be more
> conservative and to avoid false patch by adding human analysis.

For the returnvar.cocci false-positives, I wonder if it's possible to find them
using another coccinelle helper that detects badly formed macros which
access variables out of scope. I can't think of how this would be expressed,
but maybe someone has an idea.

Something else went wrong in this particular patch,  and I can't explain
how this happened: the subject line contains the name of the wrong platform,
"dove" rather than "omap2". My guess is that this was human error copying
the subject line from another patch, but if this came from a script, you
may want to check how this gets generated.

       Arnd