linux-kernel - Re: [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and ARCH_ENABLE_TAGGED

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Message-Id: <5a92ba37-69ae-477e-9747-315d41d3206e@www.fastmail.com>
Date:   Wed, 29 Jun 2022 19:04:24 -0700
From:   "Andy Lutomirski" <luto@...nel.org>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Cc:     "Rick P Edgecombe" <rick.p.edgecombe@...el.com>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        "H.J. Lu" <hjl.tools@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "Dave Hansen" <dave.hansen@...ux.intel.com>,
        "andreyknvl@...il.com" <andreyknvl@...il.com>,
        "kcc@...gle.com" <kcc@...gle.com>,
        "Andi Kleen" <ak@...ux.intel.com>,
        "dvyukov@...gle.com" <dvyukov@...gle.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "ryabinin.a.a@...il.com" <ryabinin.a.a@...il.com>,
        "glider@...gle.com" <glider@...gle.com>
Subject: Re: [PATCHv3 6/8] x86/mm: Provide ARCH_GET_UNTAG_MASK and
 ARCH_ENABLE_TAGGED_ADDR



On Thu, Jun 16, 2022, at 9:54 AM, Kirill A. Shutemov wrote:
> On Thu, Jun 16, 2022 at 11:44:59AM +0200, Peter Zijlstra wrote:
>> > get_nr_threads() is the wrong thing.  Either look at mm->mm_users or
>> > find a way to get rid of this restriction entirely.
>> 
>> mm->mm_users should indeed be sufficient here.
>
> Hm. kthread_use_mm() doesn't bump mm_users. Do we care?

I think the idea is that the kthread in question is expected to hold an mm_users reference. 

>
> -- 
>  Kirill A. Shutemov