linux-kernel - Re: [PATCH] perf/x86/amd/uncore: fix error codes in amd_uncore

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Message-ID: <ZSkInflBriOL9V3M@gmail.com>
Date:   Fri, 13 Oct 2023 11:06:37 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Sandipan Das <sandipan.das@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Uros Bizjak <ubizjak@...il.com>
Subject: Re: [PATCH] perf/x86/amd/uncore: fix error codes in amd_uncore_init()


* Dan Carpenter <dan.carpenter@...aro.org> wrote:

> On Fri, Oct 13, 2023 at 09:30:46AM +0200, Ingo Molnar wrote:
>
> > Ugh, why on Earth didn't GCC warn about this? The bad pattern is pretty 
> > simple & obvious once pointed out ... compilers should have no trouble 
> > realizing that 'ret' is returned uninitialized in some of these control 
> > paths. Yet not a peep from the compiler ...
> 
> We disabled that warning years ago (5?) because GCC had too many false 
> positives.

GCC had some pretty bogus notions about 'possible' uninitialized use that 
encouraged some bad code patterns, but in this case there's readily 
provable uninitialized use, that a compiler should warn about.

Is it possible to disable just the unreliable, probabilistic part of GCC's 
uninitialized variables warnings?

Thanks,

	Ingo