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Date:   Wed, 21 Nov 2018 12:31:50 -0800
From:   Matthew Wilcox <willy@infradead.org>
To:     Daniel Colascione <dancol@google.com>
Cc:     linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        timmurray@google.com, primiano@google.com, joelaf@google.com,
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        Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [PATCH] Add /proc/pid_generation
Message-ID: <20181121203150.GK3065@bombadil.infradead.org>
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On Wed, Nov 21, 2018 at 12:14:44PM -0800, Daniel Colascione wrote:
> This change adds a per-pid-namespace 64-bit generation number,
> incremented on PID rollover, and exposes it via a new proc file
> /proc/pid_generation. By examining this file before and after /proc
> enumeration, user code can detect the potential reuse of a PID and
> restart the task enumeration process, repeating until it gets a
> coherent snapshot.
> 
> PID rollover ought to be rare, so in practice, scan repetitions will
> be rare.

Then why does it need to be 64-bit?