linux-kernel - Re: [PATCH] blk-cgroup: Remove unnecessary rcu_read

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Message-ID: <1dad86bb-ae31-5bf8-5810-9e81c68be8ff@kernel.dk>
Date:   Wed, 18 May 2022 16:29:35 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Marek Szyprowski <m.szyprowski@...sung.com>, bh1scw@...il.com,
        tj@...nel.org
Cc:     cgroups@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, songmuchun@...edance.com
Subject: Re: [PATCH] blk-cgroup: Remove unnecessary rcu_read_lock/unlock()

On 5/18/22 1:28 PM, Marek Szyprowski wrote:
> On 16.05.2022 19:39, bh1scw@...il.com wrote:
>> From: Fanjun Kong <bh1scw@...il.com>
>>
>> spin_lock_irq/spin_unlock_irq contains preempt_disable/enable().
>> Which can serve as RCU read-side critical region, so remove
>> rcu_read_lock/unlock().
>>
>> Signed-off-by: Fanjun Kong <bh1scw@...il.com>
> 
> This patch landed in today's linux next-20220518 as commit 77c570a1ea85 
> ("blk-cgroup: Remove unnecessary rcu_read_lock/unlock()").
> 
> Unfortunately it triggers the following warning on ARM64 based Raspberry 
> Pi 4B board:>
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 1 at block/blk-cgroup.c:301 blkg_create+0x398/0x4e0

Should this use rcu_read_lock_any_held() rather than rcu_read_lock_held()?

-- 
Jens Axboe