Messages in this thread | | | Subject | Re: [Regression] Missing device nodes for ETR, ETF and STM after CONFIG_UEVENT_HELPER=n | From | Sai Prakash Ranjan <> | Date | Fri, 26 Jul 2019 15:54:18 +0530 |
| |
On 7/26/2019 3:49 PM, Greg Kroah-Hartman wrote: > On Fri, Jul 26, 2019 at 03:44:40PM +0530, Sai Prakash Ranjan wrote: >> On 7/26/2019 3:14 PM, Sai Prakash Ranjan wrote: >>> On 7/26/2019 2:11 PM, 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 am not mounting devtmpfs. However >>> >>> CONFIG_DEVTMPFS=y >>> CONFIG_DEVTMPFS_MOUNT=y >>> >> >> Ok my initramfs is using mdev: >> >> */sbin/mdev -s* >> >> This somehow is not mounting etr, etf, stm devices when uevent-helper is >> disabled. Anyways as Suzuki mentioned, using devtmpfs does fix the issue. > > Last I looked (many years ago) mdev requires uevent-helper in order for > it to work. I recommend that if you rely on mdev to keep that option > enabled, or to just use devtmpfs and udev :) >
Ok that explains, its not a hard requirement for me to use mdev. I just happen to stumble upon this issue. Thanks for your time :)
Thanks, Sai
-- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
| |