linux-kernel - Re: [PATCH] x86,mm: print likely CPU at segfault time

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Date:   Wed, 21 Jul 2021 22:38:32 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Rik van Riel <riel@...riel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>, kernel-team@...com,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org
Subject: Re: [PATCH] x86,mm: print likely CPU at segfault time

On Mon, Jul 19 2021 at 15:34, Rik van Riel wrote:

> On Mon, 2021-07-19 at 12:20 -0700, Dave Hansen wrote:
>
>> If it's as trivial as:
>> 
>>         printk(KERN_CONT " on cpu/core %d/%d",
>>                 raw_smp_processor_id(),
>>                 topology_core_id(raw_smp_processor_id()));
>> 
>> it would be handy.  But, it's also not hard to look at 10 segfaults,
>> see
>> that they happened only on 2 CPUs and realize that hyperthreading is
>> enabled.
>
> One problem with topology_core_id() is that that, on a
> multi-socket system, the core number may not be unique.

Just add topology_physical_package_id() and you have a complete picture.

Thanks,

        tglx