On Mon, Sep 29, 2014 at 11:22:08PM +0200, Luis R. Rodriguez wrote:

On Sun, Sep 28, 2014 at 11:03:29AM -0400, Tejun Heo wrote:

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Hello,

On Fri, Sep 26, 2014 at 02:57:17PM -0700, Luis R. Rodriguez wrote:
...

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Systemd should consider enabling async probe on device drivers
it loads through systemd-udev but probably does not want to
enable it for modules loaded through systemd-modules-load
(modules-load.d). At least on my booting enablign async probe
for all modules fails to boot as such in order to make this

Did you find out why boot failed with those modules?

No, it seems this was early in boot and I haven't been able to capture the logs
yet of the faults. More on this below.

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a bit more useful we whitelist a few buses where it should be
at least in theory safe to try to enable async probe. This
way even if systemd tried to ask to enable async probe for all
its device drivers the kernel won't blindly do this. We also
have the sync_probe flag which device drivers can themselves
enable *iff* its known the device driver should never async
probe.

In order to help *test* things folks can use the bus.safe_mod_async_probe=1
kernel parameter which will work as if userspace would have
requested all modules to load with async probe. Daring folks can
also use bus.force_mod_async_probe=1 which will enable asynch probe
even on buses not tested in any way yet, if you use that though
you're on your own.

If those two knobs are meant for debugging, let's please make that
fact immediately evident.  e.g. Make them ugly boot params like
"__DEVEL__driver_force_mod_async_probe".  Devel/debug options ending
up becoming stable interface are really nasty.

Sure make sense, I wasn't quite sure how to make this quite clear,
a naming convention seems good to me but I also had added at least
a print about this on the log. Ideally I think a TAIN_DEBUG would
be best and it seems it could be useful for many other cases in
the kernel, we could also just re-use TAINT_CRAP as well. Thoughts?
Greg?

TAINT_CRAP is for drivers/staging/ code, don't try to repurpose it for
some other horrid option.  There's no reason we can't add more taint
flags for this.

greg k-h