Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Sun, 21 Mar 2021 19:30:37 +0000
From:   Qais Yousef <qais.yousef@arm.com>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     valentin.schneider@arm.com, tglx@linutronix.de, mingo@kernel.org,
        bigeasy@linutronix.de, swood@redhat.com, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com, vincent.donnefort@arm.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] cpumask: Introduce DYING mask
Message-ID: <20210321193037.7o3mqcmwjthbos7n@e107158-lin>
References: <20210310145258.899619710@infradead.org>
 <20210310150109.151441252@infradead.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20210310150109.151441252@infradead.org>
Precedence: bulk

On 03/10/21 15:53, Peter Zijlstra wrote:
> --- a/kernel/cpu.c
> +++ b/kernel/cpu.c
> @@ -160,6 +160,9 @@ static int cpuhp_invoke_callback(unsigne
>  	int (*cb)(unsigned int cpu);
>  	int ret, cnt;
>  
> +	if (bringup != !cpu_dying(cpu))

nit: this condition is hard to read

> +		set_cpu_dying(cpu, !bringup);

since cpu_dying() will do cpumask_test_cpu(), are we saving  much if we
unconditionally call set_cpu_dying(cpu, !bringup) which performs
cpumask_{set, clear}_cpu()?

> +
>  	if (st->fail == state) {
>  		st->fail = CPUHP_INVALID;
>  		return -EAGAIN;

Thanks

--
Qais yousef