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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Marcelo Tosatti <mtosatti@redhat.com>,
        Nitesh Narayan Lal <nitesh@redhat.com>
Cc:     Robin Murphy <robin.murphy@arm.com>,
        Nitesh Narayan Lal <nitesh@redhat.com>,
        linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        frederic@kernel.org, juri.lelli@redhat.com, abelits@marvell.com,
        bhelgaas@google.com, linux-pci@vger.kernel.org,
        rostedt@goodmis.org, mingo@kernel.org, peterz@infradead.org,
        davem@davemloft.net, akpm@linux-foundation.org,
        sfr@canb.auug.org.au, stephen@networkplumber.org,
        rppt@linux.vnet.ibm.com, jinyuqi@huawei.com,
        zhangshaokun@hisilicon.com
Subject: Re: [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs
In-Reply-To: <20210128165903.GB38339@fuller.cnet>
References: <20200625223443.2684-1-nitesh@redhat.com> <20200625223443.2684-2-nitesh@redhat.com> <3e9ce666-c9cd-391b-52b6-3471fe2be2e6@arm.com> <20210127121939.GA54725@fuller.cnet> <87r1m5can2.fsf@nanos.tec.linutronix.de> <20210128165903.GB38339@fuller.cnet>
Date:   Thu, 28 Jan 2021 21:01:37 +0100
Message-ID: <87h7n0de5a.fsf@nanos.tec.linutronix.de>
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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