linux-kernel - Re: [PATCH 12/17] workqueue: Implement disable/enable for (delayed) work items

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Message-ID: <ZdTxisk3zp_eXDVb@slm.duckdns.org>
Date: Tue, 20 Feb 2024 08:38:02 -1000
From: Tejun Heo <tj@...nel.org>
To: Lai Jiangshan <jiangshanlai@...il.com>
Cc: torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	allen.lkml@...il.com, kernel-team@...a.com
Subject: Re: [PATCH 12/17] workqueue: Implement disable/enable for (delayed)
 work items

Hello,

On Tue, Feb 20, 2024 at 03:22:26PM +0800, Lai Jiangshan wrote:
> > - A work item carries 10bit disable count in work->data while not queued.
> >   The access to the count is synchronized by the PENDING bit like all other
> >   parts of work->data.
> 
> It is 16bit disable count in the code.

Fixed.

> It misses the same handling  at queue_work_node() and queue_rcu_work().

Oops, fixed queued_work_node() but I don't think the latter is an issue
given that calling work interface functions in the embedded work is not
supported and rcu_work can't even be canceled.

I'm not quite sure flush_delayed_work() is safe. Will think more about that.

> But it is bad idea to cancel or disable rcu work since it can be possibly
> in the rcu's waiting list.

Yeah, this isn't currently supported. If we want to add this, we'd have to
have a mechanism to shoot it down from RCU's pending list.

Thanks.

-- 
tejun