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From:   Thomas Gleixner <tglx@linutronix.de>
To:     Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
        Ming Lei <ming.lei@redhat.com>
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Subject: Re: io_uring vs CPU hotplug, was Re: [PATCH 5/9] blk-mq: don't set data->ctx and data->hctx in blk_mq_alloc_request_hctx
In-Reply-To: <448d3660-0d83-889b-001f-a09ea53fa117@kernel.dk>
References: <20200518093155.GB35380@T590> <87imgty15d.fsf@nanos.tec.linutronix.de> <20200518115454.GA46364@T590> <20200518131634.GA645@lst.de> <20200518141107.GA50374@T590> <20200518165619.GA17465@lst.de> <20200519015420.GA70957@T590> <20200519153000.GB22286@lst.de> <20200520011823.GA415158@T590> <20200520030424.GI416136@T590> <20200520080357.GA4197@lst.de> <8f893bb8-66a9-d311-ebd8-d5ccd8302a0d@kernel.dk> <448d3660-0d83-889b-001f-a09ea53fa117@kernel.dk>
Date:   Wed, 20 May 2020 21:41:05 +0200
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Jens Axboe <axboe@kernel.dk> writes:
> On 5/20/20 8:45 AM, Jens Axboe wrote:
>> It just uses kthread_create_on_cpu(), nothing home grown. Pretty sure
>> they just break affinity if that CPU goes offline.
>
> Just checked, and it works fine for me. If I create an SQPOLL ring with
> SQ_AFF set and bound to CPU 3, if CPU 3 goes offline, then the kthread
> just appears unbound but runs just fine. When CPU 3 comes online again,
> the mask appears correct.

When exactly during the unplug operation is it unbound?

Thanks,

        tglx