linux-kernel - RE: [PATCH 1/3] driver core: enable drivers to use deferred probe from init

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Message-ID: <B5657A6538887040AD3A81F1008BEC63B07066@avmb3.qlogic.org>
Date:	Mon, 28 Jul 2014 18:30:29 +0000
From:	Yuval Mintz <Yuval.Mintz@...gic.com>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
CC:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Joseph Salisbury <joseph.salisbury@...onical.com>,
	Kay Sievers <kay@...y.org>,
	"One Thousand Gnomes" <gnomes@...rguk.ukuu.org.uk>,
	Tim Gardner <tim.gardner@...onical.com>,
	Pierre Fersing <pierre-fersing@...rref.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Benjamin Poirier <bpoirier@...e.de>,
	Nagalakshmi Nandigama <nagalakshmi.nandigama@...gotech.com>,
	Praveen Krishnamoorthy <praveen.krishnamoorthy@...gotech.com>,
	Sreekanth Reddy <sreekanth.reddy@...gotech.com>,
	Abhijit Mahajan <abhijit.mahajan@...gotech.com>,
	Hariprasad S <hariprasad@...lsio.com>,
	Santosh Rastapur <santosh@...lsio.com>,
	"MPT-FusionLinux.pdl@...gotech.com" 
	<MPT-FusionLinux.pdl@...gotech.com>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: RE: [PATCH 1/3] driver core: enable drivers to use deferred probe
	from init

> On Mon, Jul 28, 2014 at 06:52:48PM +0200, Luis R. Rodriguez wrote:
> > On Mon, Jul 28, 2014 at 03:46:32PM +0000, Yuval Mintz wrote:
> > > Sorry for not being clear, but I didn't meant 'what guarantees that the device
> > > will be added to the deferred probe', but rather what guarantees that the
> > > deferred workqueue will be scheduled.
> > >
> > > To the best of my knowledge the deferring mechanism works only if one device
> > > is dependent upon another, e.g., for Multi-function devices where one device
> > > probe is dependent upon the others - which are soon-to-be probed.
> >
> > The workqueue will be kicked when driver_deferred_probe_trigger() gets
> > poked, we do that in the late_initcall(deferred_probe_initcall), it
> > also gets flushed there with a flush_workqueue(deferred_wq).

> But come to think of it that will work well for devices already plugged in
> so indeed I think that driver_deferred_probe_add() needs a check added
> for for if (!driver_deferred_probe_enable) then we have to
> driver_deferred_probe_trigger(). The driver_deferred_probe_enable is set
> to false upon init, but later on late init it gets set to true so with
> that check we'd  only generate the trigger after late init call.

> I can fold that in the v2.

>   Luis

But what about modules being added after the init-calls? If they try try to use this
mechanism, what guarantees they'll eventually get probed?
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