Re: [PATCH v2 12/14] torture: Replace cpu_up/down with device_online/offline

Paul E. McKenney
2019-11-27T21:47:28Z

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@arm.com>
> CC: Davidlohr Bueso <dave@stgolabs.net>
> CC: "Paul E. McKenney" <paulmck@kernel.org>
> CC: Josh Triplett <josh@joshtriplett.org>
> CC: linux-kernel@vger.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
>