linux-kernel - Re: [PATCH v2 7/7] driver-core: add preferred async probe option for built-in and modules

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Message-ID: <CAB=NE6V_1yyYPhzbV_yRzt7fg=_8yF2YYNBz4qH_2TbH0nozcw@mail.gmail.com>
Date:	Tue, 7 Oct 2014 11:55:16 -0700
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Takashi Iwai <tiwai@...e.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Tom Gundersen <teg@...m.no>,
	Robert Milasan <rmilasan@...e.com>, werner@...e.com,
	Oleg Nesterov <oleg@...hat.com>, hare <hare@...e.com>,
	Benjamin Poirier <bpoirier@...e.de>,
	Santosh Rastapur <santosh@...lsio.com>,
	Petr Mladek <pmladek@...e.cz>, dbueso@...e.com,
	"linux-kernel@...r.kernel.org" <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>,
	Nagalakshmi Nandigama <nagalakshmi.nandigama@...gotech.com>,
	Praveen Krishnamoorthy <praveen.krishnamoorthy@...gotech.com>,
	Sreekanth Reddy <sreekanth.reddy@...gotech.com>,
	Abhijit Mahajan <abhijit.mahajan@...gotech.com>,
	Casey Leedom <leedom@...lsio.com>,
	Hariprasad S <hariprasad@...lsio.com>,
	"mpt-fusionlinux.pdl" <MPT-FusionLinux.pdl@...gotech.com>,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 7/7] driver-core: add preferred async probe option for
 built-in and modules

On Tue, Oct 7, 2014 at 10:55 AM, Tejun Heo <tj@...nel.org> wrote:
> Hello,
>
> On Tue, Oct 07, 2014 at 07:50:10PM +0200, Luis R. Rodriguez wrote:
>> On Tue, Oct 07, 2014 at 01:34:04PM -0400, Tejun Heo wrote:
>> > But you can create a new workqueue and queue all the async probing
>> > work items there and flush the workqueue right after
>> > async_synchronize_full().
>>
>> On second thought I would prefer to avoid this, I see this being good
>> to help with old userspace but other than that I don't see a requirement
>> for new userspace. Do you?
>
> Hmmm... we batch up and do everything parallel, so I'm not sure how
> much gain we'd be looking at by not waiting for at the end before
> jumping into the userland.  Also, it's a bit of an orthogonal issue.
> If we wanna skip such synchornization point before passing control to
> userland, why are we applying that to this but not
> async_synchronize_full() which has a far larger impact?  It's weird to
> synchronize one while not the other, so yeah, if there are actual
> benefits we can consider it but let's do it separately.

OK I'll just kill bus.enable_kern_async=1 to enable built-in async
probe support *and* also have prefer_async_probe *always* be
respected, whether modular or not.

  Luis
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