Re: [patch V2 08/24] hwtracing/coresight-etm3x: Use cpuhp_setup_state_nocalls_cpuslocked()

[Mathieu Poirier]

On 18 April 2017 at 11:04, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
>
> etm_probe() holds get_online_cpus() while invoking
> cpuhp_setup_state_nocalls().
>
> cpuhp_setup_state_nocalls() invokes get_online_cpus() as well. This is
> correct, but prevents the conversion of the hotplug locking to a percpu
> rwsem.
>
> Use cpuhp_setup_state_nocalls_cpuslocked() to avoid the nested call.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>
> ---
>  drivers/hwtracing/coresight/coresight-etm3x.c |   12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
>
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> @@ -803,12 +803,12 @@ static int etm_probe(struct amba_device
>                 dev_err(dev, "ETM arch init failed\n");
>
>         if (!etm_count++) {
> -               cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING,
> -                                         "arm/coresight:starting",
> -                                         etm_starting_cpu, etm_dying_cpu);
> -               ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
> -                                               "arm/coresight:online",
> -                                               etm_online_cpu, NULL);
> +               cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING,
> +                                                    "arm/coresight:starting",
> +                                                    etm_starting_cpu, etm_dying_cpu);
> +               ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
> +                                                          "arm/coresight:online",
> +                                                          etm_online_cpu, NULL);
>                 if (ret < 0)
>                         goto err_arch_supported;
>                 hp_online = ret;
>

Acked-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>