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Date:   Thu, 22 Nov 2018 16:58:34 +0300
From:   Cyrill Gorcunov <gorcunov@gmail.com>
To:     Andy Lutomirski <luto@amacapital.net>
Cc:     Daniel Colascione <dancol@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Jonathan Corbet <corbet@lwn.net>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>, Roman Gushchin <guro@fb.com>,
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Subject: Re: [PATCH v2] Add /proc/pid_gen
Message-ID: <20181122135834.GA29449@uranus>
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On Wed, Nov 21, 2018 at 04:35:34PM -0700, Andy Lutomirski wrote:
> > 
> > I'm going to have Android's systrace and Perfetto use this approach.
> > Exactly how many tools signed up to use this feature do you need?
> > 
> >> Those people are the intended audience and the
> >> best-positioned reviewers so let's hear from them?
> > 
> > I'm writing plenty of trace analysis tools myself, so I'm part of this
> > intended audience. Other tracing tool authors have told me about
> > out-of-tree hacks for process atomic snapshots via ftrace events. This
> > approach avoids the necessity of these more-invasive hacks.
> 
> Would a tracepoint for pid reuse solve your problem?

FWIW we've had similar problem in criu for memory snapshotting,
because memory data is PID-driven and snapshots are rather
discrete events. So we use task_struct::real_start_time as
a second guard agains pid reuse.