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Date:   Mon, 23 Nov 2020 15:38:36 +1100
From:   Balbir Singh <bsingharora@gmail.com>
To:     "Joel Fernandes (Google)" <joel@joelfernandes.org>
Cc:     Nishanth Aravamudan <naravamudan@digitalocean.com>,
        Julien Desfossez <jdesfossez@digitalocean.com>,
        Peter Zijlstra <peterz@infradead.org>,
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Subject: Re: [PATCH -tip 13/32] sched: Trivial forced-newidle balancer
Message-ID: <20201123043836.GG110669@balbir-desktop>
References: <20201117232003.3580179-1-joel@joelfernandes.org>
 <20201117232003.3580179-14-joel@joelfernandes.org>
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On Tue, Nov 17, 2020 at 06:19:43PM -0500, Joel Fernandes (Google) wrote:
> From: Peter Zijlstra <peterz@infradead.org>
> 
> When a sibling is forced-idle to match the core-cookie; search for
> matching tasks to fill the core.
> 
> rcu_read_unlock() can incur an infrequent deadlock in
> sched_core_balance(). Fix this by using the RCU-sched flavor instead.
> 
...
> +
> +		if (p->core_occupation > dst->idle->core_occupation)
> +			goto next;
> +

I am unable to understand this check, a comment or clarification in the
changelog will help. I presume we are looking at either one or two cpus
to define the core_occupation and we expect to match it against the
destination CPU.

Balbir Singh.