Re: [PATCH v2 0/8] Asynchronous device/driver probing support

Dmitry Torokhov
2015-04-06T16:22:59Z

On Tue, Mar 31, 2015 at 04:39:49PM -0400, Tejun Heo wrote:
> On Mon, Mar 30, 2015 at 04:20:02PM -0700, 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.
> >
> > Changes from v1:
> >
> > - Changed verbage in change logs and code to emphasise that
> > PROBE_PREFER_ASYNCHRONOUS is a temporary measure and the end goal is
> > to enable asynchronous probing by default, as requested by Tejun.
>
> Looks good to me. Please feel free to add
>
> Acked-by: Tejun Heo <tj@kernel.org>

Greg, it would be great if it could make it in 4.1.

Thanks!

--
Dmitry