On Fri, Mar 2, 2018 at 5:31 AM, Masahiro Yamada
<yamada.masahiro@xxxxxxxxxxxxx> wrote:
> Commit fbe98bb9ed3d ("kconfig: Fix defconfig when one choice menu
> selects options that another choice menu depends on") fixed defconfig
> when two choices interact (i.e. calculating the visibility of a choice
> requires to calculate another choice).
>
> The test code in that commit log was based on the real world example,
> and complicated. So, I shrunk it down to the following:
>
> defconfig.choice:
> ---8<---
> CONFIG_CHOICE_VAL0=y
> ---8<---
>
> ---8<---
> config MODULES
> bool "Enable loadable module support"
> option modules
> default y
>
> choice
> prompt "Choice"
>
> config CHOICE_VAL0
> tristate "Choice 0"
>
> config CHOICE_VAL1
> tristate "Choice 1"
>
> endchoice
>
> choice
> prompt "Another choice"
> depends on CHOICE_VAL0
>
> config DUMMY
> bool "dummy"
>
> endchoice
> ---8<---
>
> Prior to commit fbe98bb9ed3d,
>
> $ scripts/kconfig/conf --defconfig=defconfig.choice Kconfig.choice
>
> resulted in:
>
> CONFIG_MODULES=y
> CONFIG_CHOICE_VAL0=m
> # CONFIG_CHOICE_VAL1 is not set
> CONFIG_DUMMY=y
>
> where the expected result would be:
>
> CONFIG_MODULES=y
> CONFIG_CHOICE_VAL0=y
> # CONFIG_CHOICE_VAL1 is not set
> CONFIG_DUMMY=y
>
> Roughly, this weird behavior happened like this:
>
> Symbols are calculated a couple of times. First, all symbols are
> calculated in conf_read(). The first 'choice' is evaluated to 'y'
> due to the SYMBOL_DEF_USER flag, but sym_calc_choice() clears it
> unless all of its choice values are explicitly set by the user.
>
> conf_set_all_new_symbols() clears all SYMBOL_VALID flags. Then, only
> choices are calculated. At this point, the SYMBOL_DEF_USER for the
> first choice is unset, so, it is evaluated to 'm'. (this is weird)
This is because tristate choices start out in m mode btw (they have an
implicit select of 'm && <visibibility>' on them, added add the end of
menu_finalize()).
> set_all_choice_values() sets SYMBOL_DEF_USER again to choice symbols.
>
> When calculating the second choice, due to 'depends on CHOICE_VAL0',
> it triggers the calculation of CHOICE_VAL0. As a result, SYMBOL_VALID
> is set for CHOICE_VAL0.
>
> Symbols except choices get the final chance of re-calculation in
> conf_write(). In a normal case, CHOICE_VAL0 would be re-caluculated,
> then the first choice would be indirectly re-calculated with the
> SYMBOL_DEF_USER which has been set by set_all_choice_values(), which
> would be evaluated to 'y'. But, in this case, CHOICE_VAL0 has been
> marked SYMBOL_VALID, so it is simply skipped. Then, =m is written out
> to the .config file.
>
> Add a unit test for this naive case.
At a high level, I think the problem is that the choice mode is
forgotten. It should be y because of the CONFIG_CHOICE_VAL0=y
assignment, but reverts back to m temporarily, and during that window
a choice symbol is evaluated and gets the wrong value.
I wonder if all this twisty code and the weird flags
(SYMBOL_NEED_SET_CHOICE_VALUES... hmm) are required. Perhaps an extra
invalidation or the like would be enough.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
> ---
>
> Changes in v2:
> - Newly added
>
> scripts/kconfig/tests/inter_choice/Kconfig | 24 ++++++++++++++++++++++
> scripts/kconfig/tests/inter_choice/__init__.py | 14 +++++++++++++
> scripts/kconfig/tests/inter_choice/defconfig | 1 +
> scripts/kconfig/tests/inter_choice/expected_config | 4 ++++
> 4 files changed, 43 insertions(+)
> create mode 100644 scripts/kconfig/tests/inter_choice/Kconfig
> create mode 100644 scripts/kconfig/tests/inter_choice/__init__.py
> create mode 100644 scripts/kconfig/tests/inter_choice/defconfig
> create mode 100644 scripts/kconfig/tests/inter_choice/expected_config
>
> diff --git a/scripts/kconfig/tests/inter_choice/Kconfig b/scripts/kconfig/tests/inter_choice/Kconfig
> new file mode 100644
> index 0000000..57d55c4
> --- /dev/null
> +++ b/scripts/kconfig/tests/inter_choice/Kconfig
> @@ -0,0 +1,24 @@
> +config MODULES
> + bool "Enable loadable module support"
> + option modules
> + default y
> +
> +choice
> + prompt "Choice"
> +
> +config CHOICE_VAL0
> + tristate "Choice 0"
> +
> +config CHOIVE_VAL1
> + tristate "Choice 1"
> +
> +endchoice
> +
> +choice
> + prompt "Another choice"
> + depends on CHOICE_VAL0
> +
> +config DUMMY
> + bool "dummy"
> +
> +endchoice
> diff --git a/scripts/kconfig/tests/inter_choice/__init__.py b/scripts/kconfig/tests/inter_choice/__init__.py
> new file mode 100644
> index 0000000..5c7fc36
> --- /dev/null
> +++ b/scripts/kconfig/tests/inter_choice/__init__.py
> @@ -0,0 +1,14 @@
> +"""
> +Do not affect user-assigned choice value by another choice.
> +
> +Handling of state flags for choices is complecated. In old days,
> +the defconfig result of a choice could be affected by another choice
> +if those choices interact by 'depends on', 'select', etc.
> +
> +Related Linux commit: fbe98bb9ed3dae23e320c6b113e35f129538d14a
> +"""
> +
> +
> +def test(conf):
> + assert conf.defconfig('defconfig') == 0
> + assert conf.config_contains('expected_config')
> diff --git a/scripts/kconfig/tests/inter_choice/defconfig b/scripts/kconfig/tests/inter_choice/defconfig
> new file mode 100644
> index 0000000..162c414
> --- /dev/null
> +++ b/scripts/kconfig/tests/inter_choice/defconfig
> @@ -0,0 +1 @@
> +CONFIG_CHOICE_VAL0=y
> diff --git a/scripts/kconfig/tests/inter_choice/expected_config b/scripts/kconfig/tests/inter_choice/expected_config
> new file mode 100644
> index 0000000..5dceefb
> --- /dev/null
> +++ b/scripts/kconfig/tests/inter_choice/expected_config
> @@ -0,0 +1,4 @@
> +CONFIG_MODULES=y
> +CONFIG_CHOICE_VAL0=y
> +# CONFIG_CHOIVE_VAL1 is not set
> +CONFIG_DUMMY=y
> --
> 2.7.4
>
Reviewed-by: Ulf Magnusson <ulfalizer@xxxxxxxxx>
This reminded me of a bug I reported ages ago, which afaict hasn't
been fixed: https://lkml.org/lkml/2012/12/5/458 (in retrospect,
sym_clear_all_valid() is cheap).
When manually patching all defconfig files in the kernel to disable
modules and running the Kconfiglib test suite, that bug triggers for a
few defconfigs. It has previously triggered for a few unpatched
defconfig files too -- see
https://github.com/ulfalizer/Kconfiglib#notes.
I just add an extra sym_clear_all_valid() at the end of
conf_set_all_new_symbols() to fix it. It'd be worth checking if that
fixes this problem too.
Cheers,
Ulf
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