linux-kernel - Re: [PATCH 6/7] workqueue: Allow cancel_work_sync() and disable_work() from atomic contexts on BH work items

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Date: Wed, 21 Feb 2024 22:32:17 -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 6/7] workqueue: Allow cancel_work_sync() and
 disable_work() from atomic contexts on BH work items

Hello,

On Thu, Feb 22, 2024 at 12:36:29PM +0800, Lai Jiangshan wrote:
> On Thu, Feb 22, 2024 at 1:43 AM Tejun Heo <tj@...nel.org> wrote:
> 
> > @@ -4077,11 +4076,37 @@ static bool __flush_work(struct work_struct *work, bool from_cancel)
> >
> >         rcu_read_lock();
> >         pool = start_flush_work(work, &barr, from_cancel);
> > +       is_bh = pool && (pool->flags & POOL_BH);
> >         rcu_read_unlock();
> >         if (!pool)
> >                 return false;
> >
> > -       wait_for_completion(&barr.done);
> > +       if (is_bh && from_cancel) {
> 
> Can "*work_data_bits(work) & WORK_OFFQ_BH" be used here?
> If so, the previous patch will not be needed.

Hmm... yeah, if we test from_cancel first, we should know that the work item
is offq and then can depend on OFFQ_BH. Maybe I'm missing something. Will
try that.

Thanks.

-- 
tejun