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Sender: Tejun Heo <htejun@gmail.com>
Date: Mon, 29 Jan 2024 23:22:19 -1000
From: Tejun Heo <tj@kernel.org>
To: torvalds@linux-foundation.org, mpatocka@redhat.com,
	Lai Jiangshan <jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org, dm-devel@lists.linux.dev,
	msnitzer@redhat.com, ignat@cloudflare.com, damien.lemoal@wdc.com,
	houtao1@huawei.com, peterz@infradead.org, mingo@kernel.org,
	netdev@vger.kernel.org, allen.lkml@gmail.com, kernel-team@meta.com
Subject: Re: [PATCHSET wq/for-6.9] workqueue: Implement BH workqueue and
 convert several tasklet users
Message-ID: <Zbi_y9w6ze7qfxQ2@slm.duckdns.org>
References: <20240130091300.2968534-1-tj@kernel.org>
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In-Reply-To: <20240130091300.2968534-1-tj@kernel.org>

Oops, forgot to cc Lai.

On Mon, Jan 29, 2024 at 11:11:47PM -1000, Tejun Heo wrote:
> Hello,
> 
> The only generic interface to execute asynchronously in the BH context is
> tasklet; however, it's marked deprecated and has some design flaws such as
> the execution code accessing the tasklet item after the execution is
> complete which can lead to subtle use-after-free in certain usage scenarios
> and less-developed flush and cancel mechanisms.
> 
> Mikulas Patocka recently reported that dm-crypt and dm-crypt are affected by
> the access-after-completion issue and suggested adding TASKLET_STATE_ONESHOT
> flag which selectively removes post-completion access while significantly
> limiting how the tasklet can be used in the following thread:
> 
>  http://lkml.kernel.org/r/82b964f0-c2c8-a2c6-5b1f-f3145dc2c8e5@redhat.com
> 
> Linus didn't like the approach and suggested extending workqueue to support
> execution from atomic context:
> 
>  http://lkml.kernel.org/r/CAHk-=wjDW53w4-YcSmgKC5RruiRLHmJ1sXeYdp_ZgVoBw=5byA@mail.gmail.com
> 
> As suggested, this patchset implements BH workqueues which are like regular
> workqueues but executes work items in the BH (softirq) context and converts
> several tasklet users.

Lai, the patchset is at:

 http://lkml.kernel.org/r/20240130091300.2968534-1-tj@kernel.org

I'd really appreciate if you can take a look.

Thanks.

-- 
tejun