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). -- 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/
