linux-kernel - Re: [Patch v4 1/3] lib: Restrict cpumask_local

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Date:   Thu, 28 Jan 2021 21:01:37 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marcelo Tosatti <mtosatti@...hat.com>,
        Nitesh Narayan Lal <nitesh@...hat.com>
Cc:     Robin Murphy <robin.murphy@....com>,
        Nitesh Narayan Lal <nitesh@...hat.com>,
        linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
        frederic@...nel.org, juri.lelli@...hat.com, abelits@...vell.com,
        bhelgaas@...gle.com, linux-pci@...r.kernel.org,
        rostedt@...dmis.org, mingo@...nel.org, peterz@...radead.org,
        davem@...emloft.net, akpm@...ux-foundation.org,
        sfr@...b.auug.org.au, stephen@...workplumber.org,
        rppt@...ux.vnet.ibm.com, jinyuqi@...wei.com,
        zhangshaokun@...ilicon.com
Subject: Re: [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs

On Thu, Jan 28 2021 at 13:59, Marcelo Tosatti wrote:
>> The whole pile wants to be reverted. It's simply broken in several ways.
>
> I was asking for your comments on interaction with CPU hotplug :-)

Which I answered in an seperate mail :)

> So housekeeping_cpumask has multiple meanings. In this case:

...

> So as long as the meaning of the flags are respected, seems
> alright.

Yes. Stuff like the managed interrupts preference for housekeeping CPUs
when a affinity mask spawns housekeeping and isolated is perfectly
fine. It's well thought out and has no limitations.

> Nitesh, is there anything preventing this from being fixed
> in userspace ? (as Thomas suggested previously).

Everything with is not managed can be steered by user space.

Thanks,

        tglx