linux-kernel - Re: [PATCH v2] blk_iocost: remove some duplicate irq disable/enables

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Message-ID: <d5b34514-aa3a-47dc-9521-d2774c1785a2@kernel.dk>
Date: Thu, 3 Oct 2024 16:06:28 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Tejun Heo <tj@...nel.org>
Cc: Dan Carpenter <dan.carpenter@...aro.org>, Waiman Long
 <longman@...hat.com>, Yu Kuai <yukuai3@...wei.com>,
 Josef Bacik <josef@...icpanda.com>, cgroups@...r.kernel.org,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
 kernel-janitors@...r.kernel.org, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v2] blk_iocost: remove some duplicate irq disable/enables

On 10/3/24 3:30 PM, Tejun Heo wrote:
> On Thu, Oct 03, 2024 at 11:22:09AM -1000, Tejun Heo wrote:
>> Yeah, that should be spin_lock_irq() for consistency but at the same time it
>> doesn't look like anything is actually grabbing that lock (or blkcg->lock
>> nesting outside of it) from an IRQ context, so no actual deadlock scenario
>> exists and lockdep doesn't trigger.
> 
> Oh, wait, it's not that. blkg_conf_prep() implies queue_lock, so the IRQ is
> disabled around it and adding _irq will trigger lockdep.

Ah makes sense, didn't realize it was nested under the queue lock. Then it
does look like it's just that one spot.

-- 
Jens Axboe