linux-kernel - Re: [PATCH v2 12/14] torture: Replace cpu_up/down with device

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Date:   Wed, 27 Nov 2019 13:47:25 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Qais Yousef <qais.yousef@....com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Josh Triplett <josh@...htriplett.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 12/14] torture: Replace cpu_up/down with
 device_online/offline

On Mon, Nov 25, 2019 at 11:27:52AM +0000, Qais Yousef wrote:
> The core device API performs extra housekeeping bits that are missing
> from directly calling cpu_up/down.
> 
> See commit a6717c01ddc2 ("powerpc/rtas: use device model APIs and
> serialization during LPM") for an example description of what might go
> wrong.
> 
> This also prepares to make cpu_up/down a private interface for anything
> but the cpu subsystem.
> 
> Signed-off-by: Qais Yousef <qais.yousef@....com>
> CC: Davidlohr Bueso <dave@...olabs.net>
> CC: "Paul E. McKenney" <paulmck@...nel.org>
> CC: Josh Triplett <josh@...htriplett.org>
> CC: linux-kernel@...r.kernel.org

Looks fine from an rcutorture viewpoint, but why not provide an API
that pulled lock_device_hotplug() and unlock_device_hotplug() into the
online/offline calls?

							Thanx, Paul

> ---
>  kernel/torture.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/torture.c b/kernel/torture.c
> index 7c13f5558b71..12115024feb2 100644
> --- a/kernel/torture.c
> +++ b/kernel/torture.c
> @@ -97,7 +97,9 @@ bool torture_offline(int cpu, long *n_offl_attempts, long *n_offl_successes,
>  			 torture_type, cpu);
>  	starttime = jiffies;
>  	(*n_offl_attempts)++;
> -	ret = cpu_down(cpu);
> +	lock_device_hotplug();
> +	ret = device_offline(get_cpu_device(cpu));
> +	unlock_device_hotplug();
>  	if (ret) {
>  		if (verbose)
>  			pr_alert("%s" TORTURE_FLAG
> @@ -148,7 +150,9 @@ bool torture_online(int cpu, long *n_onl_attempts, long *n_onl_successes,
>  			 torture_type, cpu);
>  	starttime = jiffies;
>  	(*n_onl_attempts)++;
> -	ret = cpu_up(cpu);
> +	lock_device_hotplug();
> +	ret = device_online(get_cpu_device(cpu));
> +	unlock_device_hotplug();
>  	if (ret) {
>  		if (verbose)
>  			pr_alert("%s" TORTURE_FLAG
> @@ -192,17 +196,20 @@ torture_onoff(void *arg)
>  	for_each_online_cpu(cpu)
>  		maxcpu = cpu;
>  	WARN_ON(maxcpu < 0);
> -	if (!IS_MODULE(CONFIG_TORTURE_TEST))
> +	if (!IS_MODULE(CONFIG_TORTURE_TEST)) {
> +		lock_device_hotplug();
>  		for_each_possible_cpu(cpu) {
>  			if (cpu_online(cpu))
>  				continue;
> -			ret = cpu_up(cpu);
> +			ret = device_online(get_cpu_device(cpu));
>  			if (ret && verbose) {
>  				pr_alert("%s" TORTURE_FLAG
>  					 "%s: Initial online %d: errno %d\n",
>  					 __func__, torture_type, cpu, ret);
>  			}
>  		}
> +		unlock_device_hotplug();
> +	}
>  
>  	if (maxcpu == 0) {
>  		VERBOSE_TOROUT_STRING("Only one CPU, so CPU-hotplug testing is disabled");
> -- 
> 2.17.1
>