linux-kernel - Re: [PATCH 3/7] wait.[ch]: Introduce the simple waitqueue (swait) implementation

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Message-ID: <20141020124716.465dce45@gandalf.local.home>
Date:	Mon, 20 Oct 2014 12:47:16 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	<linux-rt-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 3/7] wait.[ch]: Introduce the simple waitqueue (swait)
 implementation

On Mon, 20 Oct 2014 12:05:42 -0400
Paul Gortmaker <paul.gortmaker@...driver.com> wrote:
 
> > No. You move the items off the main list head and add it to the local
> > list and they never go back. Just start processing that local list.
> > Anything added to the main list after that will not get woken up by
> > that current wake_all call. It will need to be woken by another wake_up.
> 
> OK.  But we may not run all of the wakeups, because of:
> 
> +                       if (++woken == nr_exclusive)
> +                               break;
> 
> > 
> > > 
> > > What would need to be done as an unwind at the end of processing the
> > > local list head before it disappears from existence?  Anything?
> > 
> > Not sure what you mean here.
> 
> Per above -- can't there be "orphaned" entries that only exist on the
> local list head that didn't get processed?  What happens to those?
> 

Why not just take off nr_exclusive tasks off the main list and add
those to the local list, and then wake up all on the local list?

-- Steve
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