On Wed, Jul 08, 2015 at 05:36:04PM -0700, Dan Williams wrote: > On Mon, Jul 6, 2015 at 4:40 PM, Dmitry Torokhov > <[email protected]> wrote: > > 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 <[email protected]> > >> > 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 > >> > >> <[email protected]> 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" > >> > >> > <[email protected]> > >> > >> > > >> > >> > Signed-off-by: Dmitry Torokhov <[email protected]> > >> > >> > --- > >> > >> > 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. > > > > I think this is a red herring as I don't see how async probing is any > better at handling device registration errors. The error is logged > and "handled" by the fact that a device fails to appear, what other > action would you take? In fact libnvdimm does detect registration > failures and reports that in a parent device attribute (at least for a > region device and their namespace child devices).
What is libnvdimm behavior if you try to unload a module that tries to register a device but it failed? Memory leak or crash, right? -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
