linux-kernel - Re: [PATCH v7 1/3] block: add blk_mq_is_queue

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Message-ID: <20210315120608.GA30489@veeam.com>
Date:   Mon, 15 Mar 2021 15:06:08 +0300
From:   Sergei Shtepa <sergei.shtepa@...am.com>
To:     Christoph Hellwig <hch@...radead.org>
CC:     Mike Snitzer <snitzer@...hat.com>,
        Alasdair Kergon <agk@...hat.com>,
        Hannes Reinecke <hare@...e.de>, Jens Axboe <axboe@...nel.dk>,
        "dm-devel@...hat.com" <dm-devel@...hat.com>,
        "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        Pavel Tide <Pavel.TIde@...am.com>
Subject: Re: [PATCH v7 1/3] block: add blk_mq_is_queue_frozen()

The 03/14/2021 12:14, Christoph Hellwig wrote:
> On Fri, Mar 12, 2021 at 02:06:41PM -0500, Mike Snitzer wrote:
> > This is returning a frozen state that is immediately stale.  I don't
> > think any code calling this is providing the guarantees you think it
> > does due to the racey nature of this state once the mutex is dropped.
> 
> The code only uses it for asserts in the form of WARN_ONs.

But perhaps it is possible to come up with a more elegant solution?
I'll think about it.
-- 
Sergei Shtepa
Veeam Software developer.