linux-kernel - Re: [PATCH] RT: Add priority-queuing and priority-inheritance to workqueue infrastructure

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Message-ID: <20070801205053.GA263@tv-sign.ru>
Date:	Thu, 2 Aug 2007 00:50:53 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...e.hu>,
	Gregory Haskins <ghaskins@...ell.com>,
	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RT: Add priority-queuing and priority-inheritance to workqueue infrastructure

On 08/01, Daniel Walker wrote:
>
> On Thu, 2007-08-02 at 00:18 +0400, Oleg Nesterov wrote:
> > On 08/01, Daniel Walker wrote:
> > >
> > > On Wed, 2007-08-01 at 22:12 +0400, Oleg Nesterov wrote:
> > > 
> > > > And I personally think it is not very useful, even if it was correct.
> > > > You can create your own workqueue and change the priority of cwq->thread.
> > > 
> > > This change is more dynamic than than just setting a single priority ..
> > > There was some other work going on around this, so it's not totally
> > > clear what the benefits are ..
> > 
> > Yes, I see. But still I think the whole idea is broken, not just the
> > implementation.
> 
> It's translating priorities through the work queues, which doesn't seem
> to happen with the current implementation. A high priority, say
> SCHED_FIFO priority 99, task may have to wait for a nice -5 work queue
> to finish..

Why should that task wait?

> > What about delayed_work? insert_work() will use ->normal_prio of
> > the random interrupted process, while queue_work() uses current.
> 
> Actually it would be the priority of the timer softirq .. I think what
> is desired here would be saving the priority of the task calling
> delayed_work then using that..

But mainline calls  __do_softirq() from interrupt (irq_exit).

Oleg.

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