On Tue, Jul 7, 2015 at 1:23 AM, Luis R. Rodriguez <[email protected]> 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. > This however does not address systemd's assumption over detachment of module > load and probe. The inherent problem there was the timeout implemented and > carried in systemd over the worker that uses modlib to load modules. Upon > review the code was complex enough already and surely increasing the timeout > helps but that doesn't address all issues with a general timeout in place. > At SUSE we ended up not using a timeout for kmod built-in commands. That > leaves the original timeout purpose in place. The code for async probe was > not put in the kernel though but since its now upstream we should be able > to replace that userspace systemd work around with async probe, but systemd > folks would need to decide what they want to do. For full gory details of > this refer to: > > https://bugzilla.novell.com/show_bug.cgi?id=889297
FTR, this does not appear to be public, so I was not able to see it. >> > If not will you be at Plumbers? >> >> Yes. > > Great, Tom, Dmitry, will you be at Plumbers? Sadly, I won't make plumbers this year. Cheers, Tom -- 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/
