linux-kernel - Re: [PATCH 2/4] workqueues: Account unbound workqueue in a seperate list

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Message-ID: <20140403154303.GG23338@localhost.localdomain>
Date:	Thu, 3 Apr 2014 17:43:07 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Christoph Lameter <cl@...ux.com>,
	Kevin Hilman <khilman@...aro.org>,
	Mike Galbraith <bitbucket@...ine.de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>
Subject: Re: [PATCH 2/4] workqueues: Account unbound workqueue in a seperate
 list

On Thu, Apr 03, 2014 at 11:01:28AM -0400, Tejun Heo wrote:
> Hello,
> 
> On Thu, Apr 03, 2014 at 04:48:28PM +0200, Frederic Weisbecker wrote:
> > > Wouldn't the right thing to do would be factoring out
> > > apply_workqueue_attrs_locked()?  It's cleaner to block out addition of
> > > new workqueues while the masks are being updated anyway.
> > 
> > I'm not quite sure I get what you suggest. Do you mean have
> > apply_workqueue_attrs_locked() calling apply_workqueue_attrs() under
> > the lock on this patch?
> 
> Not sure it still matters but I was suggesting that creating
> apply_workqueue_attrs_locked() which requires the caller to handle
> locking and making apply_workqueue_attrs() a wrapper which grabs and
> releases lock around it, and using the former in locked iteration
> would work.  lol has this explanation made it any clearer or is it
> even worse now?  :)

I see, it gets a little better now :)

Maybe it still matters because I still need to iterate over unbound
workqueues to apply an update on "cpu_unbound_wqs_mask". And the list must remain
stable while I call apply_workqueue_attrs() on workqueues.

Anyway, we'll see how it looks like :)
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