Re: [PATCH] x86/platform/uv: Dont use smp_processor_id while preemptable

["Travis, Mike" <mike.travis@hpe.com>]

Thanks, I'll do that.

________________________________________
From: Hans de Goede <hdegoede@redhat.com>
Sent: Saturday, May 21, 2022 6:57 AM
To: Travis, Mike; Borislav Petkov; Dave Hansen; Ingo Molnar; Thomas Gleixner; Wahl, Steve; x86@kernel.org
Cc: Sivanich, Dimitri; Andy Shevchenko; Darren Hart; H. Peter Anvin; Anderson, Russ; linux-kernel@vger.kernel.org; platform-driver-x86@vger.kernel.org
Subject: Re: [PATCH] x86/platform/uv: Dont use smp_processor_id while preemptable

Hi Mike,

On 5/20/22 22:37, Mike Travis wrote:
> To avoid a "BUG: using smp_processor_id() in preemptible" debug
> warning message, disable preemption around use of the processor id.
>
> Signed-off-by: Mike Travis <mike.travis@hpe.com>
> Reviewed-by: Steve Wahl <steve.wahl@hpe.com>
> Reviewed-by: Dimitri Sivanich <dimitri.sivanich@hpe.com>

A git blame shows that this code has been around for quite
a while; so presumably this should be backported to some of
the stable kernel series ?

Maybe add an appropriate Cc: stable tag with the range of
kernels this should be added to and/or add a Fixes: tag?

Regards,

Hans


> ---
>  arch/x86/platform/uv/uv_time.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/platform/uv/uv_time.c b/arch/x86/platform/uv/uv_time.c
> index 54663f3e00cb..094190814a28 100644
> --- a/arch/x86/platform/uv/uv_time.c
> +++ b/arch/x86/platform/uv/uv_time.c
> @@ -275,14 +275,17 @@ static int uv_rtc_unset_timer(int cpu, int force)
>   */
>  static u64 uv_read_rtc(struct clocksource *cs)
>  {
> -     unsigned long offset;
> +     unsigned long offset, time;
> +     unsigned int cpu = get_cpu();
>
>       if (uv_get_min_hub_revision_id() == 1)
>               offset = 0;
>       else
> -             offset = (uv_blade_processor_id() * L1_CACHE_BYTES) % PAGE_SIZE;
> +             offset = (uv_cpu_blade_processor_id(cpu) * L1_CACHE_BYTES) % PAGE_SIZE;
>
> -     return (u64)uv_read_local_mmr(UVH_RTC | offset);
> +     time = (u64)uv_read_local_mmr(UVH_RTC | offset);
> +     put_cpu();
> +     return time;
>  }
>
>  /*