linux-kernel - Re: [RFC PATCH 14/17] perf: Add ioctl(REATTACH) for detached events

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Date:   Tue, 3 Oct 2017 16:50:27 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        acme@...hat.com, kirill.shutemov@...ux.intel.com,
        Borislav Petkov <bp@...en8.de>, rric@...nel.org
Subject: Re: [RFC PATCH 14/17] perf: Add ioctl(REATTACH) for detached events

On Tue, Sep 05, 2017 at 04:30:23PM +0300, Alexander Shishkin wrote:
> This adds an ioctl command to demote a detached event to a 'normal' one
> that gets destroyed when its file descriptor is closed. It can still be
> used to mmap the buffers, but not very useful otherwise.

why not simply use the fd obtained from open() on our special
filesystem?

If you open and then unlink, you loose the 'detached' state and the
filedesc is the only life-line.