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

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Date:	Thu, 2 Aug 2007 00:32:12 +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 08/02, Oleg Nesterov wrote:
>
> And I don't understand why rt_mutex_setprio() is called just before
> calling work->func(). This means that a high-priority work could
> be delayed by the low-priority ->current_work.

Aha, I missed the rt_mutex_setprio() in insert_work().

This is not good either. Suppose we have

	void work_handler(struct work_struct *self)
	{
		if (!try_lock()) {
			// try again later...
			queue_work(wq, self);
			return;
		}

		do_the_work();
	}

What if that work was queued by the low-priority thread, and
then a high-priority thread inserts a new work when work_handler()
is running?

Oleg.

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