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Message-ID: <6d48f996-6297-dc69-250b-790be6d2670c@codeaurora.org>
Date: Fri, 26 Jul 2019 15:44:40 +0530
From: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Geert Uytterhoeven <geert+renesas@...der.be>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Suzuki K Poulose <suzuki.poulose@....com>,
Leo Yan <leo.yan@...aro.org>, linux-arm-msm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [Regression] Missing device nodes for ETR, ETF and STM after
CONFIG_UEVENT_HELPER=n
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@...der.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@...der.be>
>>>>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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.
Thanks,
Sai
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