linux-kernel - Re: [PATCH 1/2] completion: move blk_wait

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Message-ID: <362c3c63-6fd9-401c-9281-e2e0c7efc14a@kernel.dk>
Date: Thu, 18 Apr 2024 09:09:07 -0600
From: Jens Axboe <axboe@...nel.dk>
To: Christoph Hellwig <hch@...radead.org>
Cc: Mikulas Patocka <mpatocka@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>, Mike Snitzer <msnitzer@...hat.com>,
 Damien Le Moal <dlemoal@...nel.org>, Ingo Molnar <mingo@...hat.com>,
 Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
 Guangwu Zhang <guazhang@...hat.com>, dm-devel@...ts.linux.dev,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] completion: move blk_wait_io to
 kernel/sched/completion.c

On 4/18/24 8:46 AM, Christoph Hellwig wrote:
> On Thu, Apr 18, 2024 at 08:30:14AM -0600, Jens Axboe wrote:
>> It certainly is a hack/work-around, but unless there are a lot more that
>> should be using something like this, I don't think adding extra core
>> complexity in terms of a special task state (or per-task flag, at least
>> that would be easier) is really warranted.
> 
> Basically any kernel thread doing on-demand work has the same problem.
> It just has an easier workaround hack, as the kernel threads can simply
> claim to do an interruptible sleep to not trigger the softlockup
> warnings.

A kernel thread can just use TASK_INTERRUPTIBLE, as it doesn't take
signals anyway. But yeah, I guess you could view that as a work-around
as well.

Outside of that, mostly only a block problem, where our sleep is always
uninterruptible. Unless there are similar hacks elsewhere in the kernel
that I'm not aware of?

-- 
Jens Axboe