* [PATCH 1/1] lib: kunit: Suppress a compilation warning of frame size
@ 2021-05-18 9:45 Zhen Lei
2021-05-18 21:38 ` Andrew Morton
0 siblings, 1 reply; 2+ messages in thread
From: Zhen Lei @ 2021-05-18 9:45 UTC (permalink / raw)
To: Andrew Morton, Shuah Khan, Vitor Massaru Iha, linux-kernel; +Cc: Zhen Lei
lib/bitfield_kunit.c: In function ‘test_bitfields_constants’:
lib/bitfield_kunit.c:93:1: warning: the frame size of 7456 bytes is larger than 2048 bytes [-Wframe-larger-than=]
}
^
As the description of BITFIELD_KUNIT in lib/Kconfig.debug, it "Only useful
for kernel devs running the KUnit test harness, and not intended for
inclusion into a production build". Therefore, it is not worth modifying
variable 'test_bitfields_constants' to clear this warning. Just suppress
it.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
lib/Makefile | 1 +
1 file changed, 1 insertion(+)
diff --git a/lib/Makefile b/lib/Makefile
index e11cfc18b6c0826..2cc359ec1fdd3e1 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -348,6 +348,7 @@ obj-$(CONFIG_OBJAGG) += objagg.o
obj-$(CONFIG_PLDMFW) += pldmfw/
# KUnit tests
+CFLAGS_bitfield_kunit.o := $(call cc-option,-Wframe-larger-than=10240)
obj-$(CONFIG_BITFIELD_KUNIT) += bitfield_kunit.o
obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
--
2.26.0.106.g9fadedd
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH 1/1] lib: kunit: Suppress a compilation warning of frame size
2021-05-18 9:45 [PATCH 1/1] lib: kunit: Suppress a compilation warning of frame size Zhen Lei
@ 2021-05-18 21:38 ` Andrew Morton
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Morton @ 2021-05-18 21:38 UTC (permalink / raw)
To: Zhen Lei; +Cc: Shuah Khan, Vitor Massaru Iha, linux-kernel, Brendan Higgins
On Tue, 18 May 2021 17:45:33 +0800 Zhen Lei <thunder.leizhen@huawei.com> wrote:
> lib/bitfield_kunit.c: In function ‘test_bitfields_constants’:
> lib/bitfield_kunit.c:93:1: warning: the frame size of 7456 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> }
> ^
>
> As the description of BITFIELD_KUNIT in lib/Kconfig.debug, it "Only useful
> for kernel devs running the KUnit test harness, and not intended for
> inclusion into a production build". Therefore, it is not worth modifying
> variable 'test_bitfields_constants' to clear this warning. Just suppress
> it.
Well, it would be better to fix this rather than hiding it. The
warning is there for a reason!
Firstly, why is this happening? Do those macros end up generating a
vast number of `kunit_assert' instances and gcc dumbly fails to reuse
the same stack slots?
It would be trivial to split test_bitfields_constants() into four
functions. Probably those should use noinline_for_stack to prevent gcc
from just inlining everything into the caller.
Also, what's up with this?
/*
* NOTE
* This whole function compiles (or at least should, if everything
* is going according to plan) to nothing after optimisation.
*/
If that's the case then why did the function use all this stack?
> diff --git a/lib/Makefile b/lib/Makefile
> index e11cfc18b6c0826..2cc359ec1fdd3e1 100644
> --- a/lib/Makefile
> +++ b/lib/Makefile
> @@ -348,6 +348,7 @@ obj-$(CONFIG_OBJAGG) += objagg.o
> obj-$(CONFIG_PLDMFW) += pldmfw/
>
> # KUnit tests
> +CFLAGS_bitfield_kunit.o := $(call cc-option,-Wframe-larger-than=10240)
> obj-$(CONFIG_BITFIELD_KUNIT) += bitfield_kunit.o
> obj-$(CONFIG_LIST_KUNIT_TEST) += list-test.o
> obj-$(CONFIG_LINEAR_RANGES_TEST) += test_linear_ranges.o
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