linux-kernel - Re: [PATCH 0/8] Asynchronous device/driver probing support

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Date:	Tue, 3 Mar 2015 13:18:52 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	"Luis R . Rodriguez" <mcgrof@...e.com>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Olof Johansson <olof@...om.net>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: Re: [PATCH 0/8] Asynchronous device/driver probing support

On Sat, Feb 07, 2015 at 06:06:15PM +0800, Greg Kroah-Hartman wrote:
> On Tue, Feb 03, 2015 at 03:12:19PM -0800, Dmitry Torokhov wrote:
> > On Fri, Jan 16, 2015 at 03:33:09PM -0800, Dmitry Torokhov wrote:
> > > This series is a combination of changes proposed by Luis a couple months
> > > ago and implementation used by Chrome OS. The issue we are trying to solve
> > > here is "slow" devices and drivers spending "too much time" in their probe()
> > > methods and it affects:
> > > 
> > > - overall kernel boot process when drivers are compiled into the kernel
> > >   and slow devices stall entire boot progress;
> > > - systemd desire to time out module loading process.
> > > 
> > > Unlike Luis' proposal we do make use of asycn_schedule() infrastructure
> > > instead of using a dedicated workqueue, so all  existing synchronization
> > > points in kernel that wait for device registration still work the same.
> > > Also, the asynchronous probing is done not only during driver registration
> > > (i.e. when devices are probed asynchronously only if they are registered
> > > before the driver), but also during device registration and deferred probe
> > > handling. This way slow devices do not stall kernel boot even when drivers
> > > are compiled into the kernel.
> > > 
> > > The last patch is for adventurous people to try and force
> > > fully-asynchronous boot. It works for me with limited success - I can boot
> > > Rockhip-based box to userspace as long as I force serial to be sychronously
> > > probed and ignore the fact that most devices are using "dummy" regulators
> > > as regulator subsystem really expects regulators to be registered in
> > > orderly fashion on OF-based systems.
> > > 
> > > Thanks,
> > > Dmitry
> > > 
> > > 
> > > Dmitry Torokhov (3):
> > >   driver-core: add asynchronous probing support for drivers
> > >   driver-core: platform_driver_probe() must probe synchronously
> > >   module: add core_param_unsafe
> > > 
> > > Luis R. Rodriguez (5):
> > >   module: add extra argument for parse_params() callback
> > >   driver-core: add driver module asynchronous probe support
> > >   driver-core: enable drivers to opt-out of async probe
> > >   amd64_edac: enforce synchronous probe
> > >   driver-core: allow forcing async probing for modules and builtins
> > > 
> > >  Documentation/kernel-parameters.txt |  13 +++
> > >  arch/powerpc/mm/hugetlbpage.c       |   4 +-
> > >  drivers/base/base.h                 |   1 +
> > >  drivers/base/bus.c                  |  31 +++++--
> > >  drivers/base/dd.c                   | 166 +++++++++++++++++++++++++++++++-----
> > >  drivers/base/platform.c             |  13 +++
> > >  drivers/edac/amd64_edac.c           |   1 +
> > >  include/linux/device.h              |  26 ++++++
> > >  include/linux/module.h              |   2 +
> > >  include/linux/moduleparam.h         |  12 ++-
> > >  init/main.c                         |  25 +++---
> > >  kernel/module.c                     |  25 +++++-
> > >  kernel/params.c                     |  11 ++-
> > >  lib/dynamic_debug.c                 |   4 +-
> > >  14 files changed, 284 insertions(+), 50 deletions(-)
> > > 
> > > -- 
> > > 2.2.0.rc0.207.ga3a616c
> > > 
> > 
> > *ping*
> 
> Sorry, I was waiting for someone else here to speak up.
> 
> It's too late for 3.20, I'll look at this when 3.20-rc1 is out, thanks,

Greg, please take another look.

Thanks!

-- 
Dmitry
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