Messages in this thread |  | | Subject | Re: [Regression] Missing device nodes for ETR, ETF and STM after CONFIG_UEVENT_HELPER=n | From | Suzuki K Poulose <> | Date | Fri, 26 Jul 2019 10:28:41 +0100 |
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On 07/26/2019 09:41 AM, Greg Kroah-Hartman wrote: > 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?
I think that should solve the issue ^^
> > 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?
Greg, those are registered as miscellaneous devices to export the trace collected (for etfs and etrs) in sysfs mode and for user-space access to allow STM tracing. So they are real devices.
Suzuki
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