linux-kernel - Re: [PATCH v2] perf: Synchronously cleanup child events

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Message-ID: <20160127175233.GA50601@ast-mbp.thefacebook.com>
Date:	Wed, 27 Jan 2016 09:52:34 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	vince@...ter.net, eranian@...gle.com,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Wang Nan <wangnan0@...wei.com>
Subject: Re: [PATCH v2] perf: Synchronously cleanup child events

On Wed, Jan 27, 2016 at 10:58:22AM +0100, Peter Zijlstra wrote:
> 
> > Meaning there gotta be always a user space process
> > that will be holding perf_event FDs.
> 
> By using fget() the BPF array thing will hold the FDs, right? I mean
> once you do a full fget() userspace can go and kill itself, the struct
> file will persists.

Right. I mistakenly thought that fget() will prevent the task
from freeing or some fs/directory resources will be hanging.
It's from anon_inode. So all good. All concerns cleared.