linux-kernel - Re: [PATCH 9/9] perf tests: Use arch__compare_symbol

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Message-ID: <20180215151018.GI30974@kernel.org>
Date:   Thu, 15 Feb 2018 12:10:18 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Jiri Olsa <jolsa@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        David Ahern <dsahern@...il.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>,
        Sandipan Das <sandipan@...ux.vnet.ibm.com>
Subject: Re: [PATCH 9/9] perf tests: Use arch__compare_symbol_names to
 compare symbols

Em Thu, Feb 15, 2018 at 08:18:51PM +0530, Naveen N. Rao escreveu:
> Arnaldo Carvalho de Melo wrote:
> > Em Thu, Feb 15, 2018 at 01:26:35PM +0100, Jiri Olsa escreveu:
> > > The symbol search called by machine__find_kernel_symbol_by_name
> > > is using internally arch__compare_symbol_names function to compare
> > > 2 symbol names, because different archs have different ways of
> > > comparing symbols. Mostly for skipping '.' prefixes and similar.
> > > 
> > > In test 1 when we try to find matching symbols in kallsyms and
> > > vmlinux, by address and by symbol name. When either is found
> > > we compare the pair symbol names  by simple strcmp, which is not
> > > good enough for reasons explained in previous paragraph.
> > > 
> > > On powerpc this can cause lockup, because even thought we found
> > > the pair, the compared names are different and don't match
> > > simple strcmp. Following code path is executed, that leads
> > > to lockup:
> > 
> > Added a:
> > 
> >     Fixes: 031b84c407c3 ("perf probe ppc: Enable matching against dot symbols automatically")
> > 
> > And CCed Naveen, the author of that patch, so that gets notified of this
> > fix.
> 
> Thanks! This does fix the test on ppc64 BE. So:
> Acked-and-Tested-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Thanks!

- Arnaldo