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Date:   Tue, 1 Dec 2020 13:56:08 -0500
From:   Joel Fernandes <joel@joelfernandes.org>
To:     Peter Zijlstra <peterz@infradead.org>
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Subject: Re: [PATCH -tip 22/32] sched: Split the cookie and setup per-task
 cookie on fork
Message-ID: <20201201185608.GA219024@google.com>
References: <20201117232003.3580179-1-joel@joelfernandes.org>
 <20201117232003.3580179-23-joel@joelfernandes.org>
 <20201125110709.GR2414@hirez.programming.kicks-ass.net>
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On Wed, Nov 25, 2020 at 12:07:09PM +0100, Peter Zijlstra wrote:
> On Tue, Nov 17, 2020 at 06:19:52PM -0500, Joel Fernandes (Google) wrote:
> > Also, for the per-task cookie, it will get weird if we use pointers of any
> > emphemeral objects. For this reason, introduce a refcounted object who's sole
> > purpose is to assign unique cookie value by way of the object's pointer.
> 
> Might be useful to explain why exactly none of the many pid_t's are
> good enough.

I thought about this already and it does not seem a good fit. When 2
processes share, it is possible that more processes are added to that logical
group. Then the original processes that share die, but if we hold on to the
pid_t or task_struct, that would be awkward. It seemed introducing a new
refcounted struct was the right way to go. I can add these details to the
change log.

thanks!

 - Joel