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Subject: Re: [PATCH V7] GCOV: Add config to check the preqequisites situation
To:     Cixi Geng <gengcixi@gmail.com>,
        Greg KH <gregkh@linuxfoundation.org>, jslaby@suse.com,
        linux-serial@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc:     Orson Zhai <orsonzhai@gmail.com>, zhang.lyra@gmail.com,
        Cixi Geng <cixi.geng1@unisoc.com>
References: <20200727085132.29754-1-gengcixi@gmail.com>
 <CAF12kFuss4AQZSBX+A2G_fWjka3C4kpf4iDWU9QJY=AWigoxqg@mail.gmail.com>
 <CAF12kFtPQ0bUKrr4X8MjLCTfFYkRVk6BRaLb30W59GwtWQd6xA@mail.gmail.com>
From:   Peter Oberparleiter <oberpar@linux.ibm.com>
Message-ID: <46289a56-3f85-fedb-53f2-6328c342f6ce@linux.ibm.com>
Date:   Thu, 22 Oct 2020 12:03:42 +0200
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On 16.09.2020 14:55, Cixi Geng wrote:
> Hi ALL：
> Not recieve more advise for a long time ,
> Can this submission be merged recently?

First off, sorry for not replying earlier.

I tried out your latest version of this patch and I don't see that my
previous comments have been addressed.

To re-iterate my point: I only see value in introducing a new
GCOV-related config symbol that is automatically selected, depending on
whether (as the name implies) all prerequisites for enabling GCOV-based
kernel profiling have been met. Such a symbol can take away the burden
of duplicating the prerequisite check as has been implemented for
GCOV_PROFILE_ALL.

I see no value in introducing a new config symbol that prompts the user
for a choice.

As it is, your patch introduces a new config symbol that prompts the
user for a choice:

$ make oldconfig
scripts/kconfig/conf  --oldconfig Kconfig
*
* Restart config...
*
*
* GCOV-based kernel profiling
*
Enable gcov-based kernel profiling (GCOV_KERNEL) [Y/n/?] y
Profile entire Kernel (GCOV_PROFILE_ALL) [N/y/?] n
Profile Kernel for prereqs (GCOV_PROFILE_PREREQS) [Y/n/?] (NEW)

We do not need this prompt. Users specify that they want GCOV-profiling
by selecting GCOV_KERNEL. They specify that they want area-specific
profiling in symbols like your proposed SERIAL_GCOV. There is no need
for a user to manually confirm that the prerequisites for enabling
are-specific profiling are met.

I have detailed the required changes that would remove the prompt in my
previous reply. I'll add it here again for your convenience:

>>> +++ b/kernel/gcov/Kconfig
>>> @@ -51,6 +51,16 @@ config GCOV_PROFILE_ALL
>>>         larger and run slower. Also be sure to exclude files from profiling
>>>         which are not linked to the kernel image to prevent linker errors.
>>>
>>> +config GCOV_PROFILE_PREREQS
>>> +       bool "Profile Kernel for prereqs"
>>> +       default y if GCOV_KERNEL && !COMPILE_TEST
>>> +       help
>>> +         This options activates profiling for the specified kernel modules.
>>> +
>>> +         When some modules need Gcov data, enable this config, then configure
>>> +         with gcov on the corresponding modules,The directories or files of
>>> +         these modules will be added profiling flags after kernel compile.
>>> +
> 
> Replace the portion above with these lines:
> 
> config GCOV_PROFILE_PREREQS
>         def_bool y if GCOV_KERNEL && !COMPILE_TEST

And to clarify: by "the portion above" I was referring to all quoted
lines prefixed with a '+' sign.


> 
> Cixi Geng <gengcixi@gmail.com> 于2020年8月20日周四 下午8:40写道：
>>
>> Hi All:
>>
>> Does this patch need more modification?
>>
>> <gengcixi@gmail.com> 于2020年7月27日周一 下午4:51写道：
>>>
>>> From: Cixi Geng <cixi.geng1@unisoc.com>
>>>
>>> Introduce new configuration option GCOV_PROFILE_PREREQS that can be
>>> used to check whether the prerequisites for enabling gcov profiling
>>> for specific files and directories are met.
>>>
>>> Only add SERIAL_GCOV for an example.
>>>
>>> Signed-off-by: Cixi Geng <cixi.geng1@unisoc.com>
>>> ---
>>>  drivers/tty/serial/Kconfig  |  7 +++++++
>>>  drivers/tty/serial/Makefile |  1 +
>>>  kernel/gcov/Kconfig         | 12 ++++++++++++
>>>  3 files changed, 20 insertions(+)
>>>
>>> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
>>> index 780908d43557..55b128b6b31d 100644
>>> --- a/drivers/tty/serial/Kconfig
>>> +++ b/drivers/tty/serial/Kconfig
>>> @@ -1576,3 +1576,10 @@ endmenu
>>>
>>>  config SERIAL_MCTRL_GPIO
>>>         tristate
>>> +
>>> +config SERIAL_GCOV
>>> +       bool "Enable profile gcov for serial directory"
>>> +       depends on GCOV_PROFILE_PREREQS
>>> +       help
>>> +         The SERIAL_GCOV will add Gcov profiling flags when kernel compiles.
>>> +         Say 'Y' here if you want the gcov data for the serial directory,
>>> diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
>>> index d056ee6cca33..17272733db95 100644
>>> --- a/drivers/tty/serial/Makefile
>>> +++ b/drivers/tty/serial/Makefile
>>> @@ -3,6 +3,7 @@
>>>  # Makefile for the kernel serial device drivers.
>>>  #
>>>
>>> +GCOV_PROFILE := $(CONFIG_SERIAL_GCOV)
>>>  obj-$(CONFIG_SERIAL_CORE) += serial_core.o
>>>
>>>  obj-$(CONFIG_SERIAL_EARLYCON) += earlycon.o
>>> diff --git a/kernel/gcov/Kconfig b/kernel/gcov/Kconfig
>>> index 3110c77230c7..bb2e1fb85743 100644
>>> --- a/kernel/gcov/Kconfig
>>> +++ b/kernel/gcov/Kconfig
>>> @@ -51,4 +51,16 @@ config GCOV_PROFILE_ALL
>>>         larger and run slower. Also be sure to exclude files from profiling
>>>         which are not linked to the kernel image to prevent linker errors.
>>>
>>> +config GCOV_PROFILE_PREREQS
>>> +       bool "Profile Kernel for prereqs"
>>> +       depends on GCOV_KERNEL
>>> +       depends on  !COMPILE_TEST
>>> +       def_bool y if GCOV_KERNEL && !COMPILE_TEST
>>> +       help
>>> +         This options activates profiling for the specified kernel modules.
>>> +
>>> +         When some modules need Gcov data, enable this config, then configure
>>> +         with gcov on the corresponding modules,The directories or files of
>>> +         these modules will be added profiling flags after kernel compile.
>>> +
>>>  endmenu
>>> --
>>> 2.17.1
>>>


-- 
Peter Oberparleiter
Linux on Z Development - IBM Germany