linux-kernel - Re: [PATCH v2] perf script python: Fix dict reference counting

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Message-ID: <20180709145502.GB7917@krava>
Date:   Mon, 9 Jul 2018 16:55:02 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Janne Huttunen <janne.huttunen@...ia.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jaroslav Škarvada <jskarvad@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2] perf script python: Fix dict reference counting

On Mon, Jul 09, 2018 at 01:59:50PM +0300, Janne Huttunen wrote:
> The dictionaries are attached to the parameter tuple that steals
> the references and takes care of releasing them when appropriate.
> The code should not decrement the reference counts explicitly.
> E.g. if libpython has been built with reference debugging enabled,
> the superfluous DECREFs will trigger this error when running perf
> script:
> 
>   Fatal Python error: Objects/tupleobject.c:238 object at
>   0x7f10f2041b40 has negative ref count -1
>   Aborted (core dumped)
> 
> If the reference debugging is not enabled, the superfluous DECREFs
> might cause the dict objects to be silently released while they are
> still in use. This may trigger various other assertions or just
> cause perf crashes and/or weird and unexpected data changes in the
> stored Python objects.
> 
> Signed-off-by: Janne Huttunen <janne.huttunen@...ia.com>

Acked-by: Jiri Olsa <jolsa@...nel.org>

thanks,
jirka