linux-kernel - Re: [patch V3 7/7] rtmutex: Avoid pointless requeueing in the deadlock detection chain walk

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Message-ID: <20140610111942.668d4058@gandalf.local.home>
Date:	Tue, 10 Jun 2014 11:19:42 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Brad Mouring" <bmouring@...com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Jason Low <jason.low2@...com>
Subject: Re: [patch V3 7/7] rtmutex: Avoid pointless requeueing in the
 deadlock detection chain walk

On Tue, 10 Jun 2014 09:57:25 -0500
"Brad Mouring" <bmouring@...com> wrote:


> > +		/* Store whether owner is blocked itself and drop locks */
> > +		next_lock = task_blocked_on(task);
> task_blocked_on(task) is not clear to me, the recipient of the
> return is the only clue that hints at what the function does.

Well, this is more than confusing, it's the only user, all other users
are task_blocked_on_lock(), and this causes the code not to compile.

-- Steve


> > +		raw_spin_unlock_irqrestore(&task->pi_lock, flags);
> > +		raw_spin_unlock(&lock->wait_lock);
> > +
> > +		/* If owner is not blocked, end of chain. */
> > +		if (!next_lock)
> > +			goto out_put_task;
> > +		goto again;
> > +	}
> > +
> > +	/*
> >  	 * Store the current top waiter before doing the requeue
> >  	 * operation on @lock. We need it for the boost/deboost
> >  	 * decision below.
> > 
> > 

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