linux-kernel - Re: [PATCH 0/2] blk-mq: support physical CPU hotplug

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Message-Id: <64c62449-27d2-a0a1-c7db-d2d08a3eb893@de.ibm.com>
Date:   Fri, 12 Jan 2018 09:12:24 +0100
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Ming Lei <ming.lei@...hat.com>, Jens Axboe <axboe@...com>,
        linux-block@...r.kernel.org, Christoph Hellwig <hch@...radead.org>
Cc:     Stefan Haberland <sth@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] blk-mq: support physical CPU hotplug

I think we also need cc stable for this. The bug was introduced with 
 
commit 4b855ad37194f7bdbb200ce7a1c7051fecb56a08 upstream.
("blk-mq: Create hctx for each present CPU")

and that was even backported into 4.12 stable.



On 01/12/2018 03:53 AM, Ming Lei wrote:
> Hi,
> 
> This two patches support physical CPU hotplug, so that we can make blk-mq
> scale well when new physical CPU is added or removed, and this use case
> is normal for VM world.
> 
> Also this patchset fixes the following warning reported by Christian
> Borntraeger:
> 
> 	https://marc.info/?l=linux-block&m=151092973417143&w=2
> 
> Christoph Hellwig (2):
>   genirq/affinity: assign vectors to all possible CPUs
>   blk-mq: simplify queue mapping & schedule with each possisble CPU
> 
>  block/blk-mq.c        | 19 ++++++++-----------
>  kernel/irq/affinity.c | 30 +++++++++++++++---------------
>  2 files changed, 23 insertions(+), 26 deletions(-)
>