Messages in this thread | | | Date | Mon, 6 Jul 2015 16:40:32 -0700 | From | Dmitry Torokhov <> | Subject | Re: [PATCH 2/8] driver-core: add asynchronous probing support for drivers |
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On Tue, Jul 07, 2015 at 01:23:15AM +0200, Luis R. Rodriguez wrote: > On Sat, Jul 04, 2015 at 07:09:19AM -0700, Dan Williams wrote: > > On Fri, Jul 3, 2015 at 11:30 AM, Luis R. Rodriguez <mcgrof@suse.com> wrote: > > > On Sat, Jun 27, 2015 at 04:45:25PM -0700, Dan Williams wrote: > > >> On Mon, Mar 30, 2015 at 4:20 PM, Dmitry Torokhov > > >> <dmitry.torokhov@gmail.com> wrote: > > >> > Some devices take a long time when initializing, and not all drivers are > > >> > suited to initialize their devices when they are open. For example, > > >> > input drivers need to interrogate their devices in order to publish > > >> > device's capabilities before userspace will open them. When such drivers > > >> > are compiled into kernel they may stall entire kernel initialization. > > >> > > > >> > This change allows drivers request for their probe functions to be > > >> > called asynchronously during driver and device registration (manual > > >> > binding is still synchronous). Because async_schedule is used to perform > > >> > asynchronous calls module loading will still wait for the probing to > > >> > complete. > > >> > > > >> > Note that the end goal is to make the probing asynchronous by default, > > >> > so annotating drivers with PROBE_PREFER_ASYNCHRONOUS is a temporary > > >> > measure that allows us to speed up boot process while we validating and > > >> > fixing the rest of the drivers and preparing userspace. > > >> > > > >> > This change is based on earlier patch by "Luis R. Rodriguez" > > >> > <mcgrof@suse.com> > > >> > > > >> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com> > > >> > --- > > >> > drivers/base/base.h | 1 + > > >> > drivers/base/bus.c | 31 +++++++--- > > >> > drivers/base/dd.c | 149 ++++++++++++++++++++++++++++++++++++++++++------- > > >> > include/linux/device.h | 28 ++++++++++ > > >> > 4 files changed, 182 insertions(+), 27 deletions(-) > > >> > > >> Just noticed this patch. It caught my eye because I had a hard time > > >> getting an open coded implementation of asynchronous probing to work > > >> in the new libnvdimm subsystem. Especially the messy races of tearing > > >> things down while probing is still in flight. I ended up implementing > > >> asynchronous device registration which eliminated a lot of complexity > > >> and of course the bugs. In general I tend to think that async > > >> registration is less risky than async probe since it keeps wider > > >> portions of the traditional device model synchronous > > > > > > but its not see -DEFER_PROBE even before async probe. > > > > Except in that case you know probe has been seen by the driver at > > least once. So I see that as less of a surprise, but point taken. > > > > >> and leverages the > > >> fact that the device model is already well prepared for asynchronous > > >> arrival of devices due to hotplug. > > > > > > I think this sounds reasonable, do you have your code upstream or posted? > > > > Yes, see nd_device_register() in drivers/nvdimm/bus.c > > It should be I think rather easy for Dmitry to see if he can convert this input > driver (not yet upstream) to this API and see if the same issues are fixed.
No, I would rather not as it means we lose error handling on device registration.
Thanks.
-- Dmitry
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