linux-kernel - Re: [PATCH] perf python: Do not force closing original perf descriptor in evlist.get

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Date:   Thu, 27 Dec 2018 09:06:38 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Jiri Olsa <jolsa@...nel.org>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Ondřej Lysoněk <olysonek@...hat.com>,
        Jaroslav Škarvada <jskarvad@...hat.com>
Subject: Re: [PATCH] perf python: Do not force closing original perf
 descriptor in evlist.get_pollfd

On Wed, Dec 26, 2018 at 12:21:21PM +0100, Jiri Olsa wrote:
> Ondřej reported that when compiled with python3, the python
> extension regress in evlist.get_pollfd function behaviour.
> 
> The evlist.get_pollfd creates file objects from evlist's fds
> and returns them in the list. The python3 version also sets
> them to 'close the original descriptor' when the object die
> (is closed), by passing True via 'closefd' arg in PyFile_FromFd
> call.
> 
> The python's closefd doc says:
>   If closefd is False, the underlying file descriptor will be kept open
>   when the file is closed.
> 
> That's why following line in python3 closes all evlist fds:
>   evlist.get_pollfd()
> 
> the returned list is immediately destroyed and that takes
> down the original events fds.
> 
> Passing closefd as False to PyFile_FromFd to fix this.
> 
> Reported-by: Ondřej Lysoněk <olysonek@...hat.com>
> Link: http://lkml.kernel.org/n/tip-ru9hmsaliew8p01kr0050mvg@git.kernel.org
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>

oops, forgot to add.. and cc-ing Jaroslav Škarvada

Fixes: 66dfdff03d19 ("perf tools: Add Python 3 support")

jirka

> ---
>  tools/perf/util/python.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
> index 47628e85c5eb..dda0ac978b1e 100644
> --- a/tools/perf/util/python.c
> +++ b/tools/perf/util/python.c
> @@ -939,7 +939,8 @@ static PyObject *pyrf_evlist__get_pollfd(struct pyrf_evlist *pevlist,
>  
>  		file = PyFile_FromFile(fp, "perf", "r", NULL);
>  #else
> -		file = PyFile_FromFd(evlist->pollfd.entries[i].fd, "perf", "r", -1, NULL, NULL, NULL, 1);
> +		file = PyFile_FromFd(evlist->pollfd.entries[i].fd, "perf", "r", -1,
> +				     NULL, NULL, NULL, 0);
>  #endif
>  		if (file == NULL)
>  			goto free_list;
> -- 
> 2.17.2
>