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SubjectRe: [Regression] Missing device nodes for ETR, ETF and STM after CONFIG_UEVENT_HELPER=n
On Fri, Jul 26, 2019 at 01:50:27PM +0530, Sai Prakash Ranjan wrote:
> On 7/26/2019 12:34 PM, Greg Kroah-Hartman wrote:
> > On Fri, Jul 26, 2019 at 11:49:19AM +0530, Sai Prakash Ranjan wrote:
> > > Hi,
> > >
> > > When trying to test my coresight patches, I found that etr,etf and stm
> > > device nodes are missing from /dev.
> >
> > I have no idea what those device nodes are.
> >
> > > Bisection gives this as the bad commit.
> > >
> > > 1be01d4a57142ded23bdb9e0c8d9369e693b26cc is the first bad commit
> > > commit 1be01d4a57142ded23bdb9e0c8d9369e693b26cc
> > > Author: Geert Uytterhoeven <geert+renesas@glider.be>
> > > Date: Thu Mar 14 12:13:50 2019 +0100
> > >
> > > driver: base: Disable CONFIG_UEVENT_HELPER by default
> > >
> > > Since commit 7934779a69f1184f ("Driver-Core: disable /sbin/hotplug by
> > > default"), the help text for the /sbin/hotplug fork-bomb says
> > > "This should not be used today [...] creates a high system load, or
> > > [...] out-of-memory situations during bootup". The rationale for this
> > > was that no recent mainstream system used this anymore (in 2010!).
> > >
> > > A few years later, the complete uevent helper support was made optional
> > > in commit 86d56134f1b67d0c ("kobject: Make support for uevent_helper
> > > optional."). However, if was still left enabled by default, to support
> > > ancient userland.
> > >
> > > Time passed by, and nothing should use this anymore, so it can be
> > > disabled by default.
> > >
> > > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > >
> > > drivers/base/Kconfig | 1 -
> > > 1 file changed, 1 deletion(-)
> > >
> > >
> > > Any idea on this?
> >
> > That means that who ever created those device nodes is relying on udev
> > to do this, and is not doing the correct thing within the kernel and
> > using devtmpfs.
> >
> > Any pointers to where in the kernel those devices are trying to be
> > created?
> >
>
> Somewhere in drivers/hwtracing/coresight/* probably. I am not sure,
> Mathieu/Suzuki would be able to point you to the exact code.
>
> Also just to add on some more details, I am using *initramfs*

Are you using devtmpfs for your /dev/ mount?

If you enable this option, what does:
ls -l /dev/etr
ls -l /dev/etf
ls -l /dev/stm
result in?

What are these device nodes for? Are they symlinks? Real devices that
show up in /sys/dev/char/ as a real value? Or something else?

Do you have udev rules that create these nodes somehow?

thanks,

greg k-h

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