From: Guenter Roeck <linux@roeck-us.net>
To: linux-kselftest@vger.kernel.org
Cc: "David Airlie" <airlied@gmail.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Maíra Canal" <mcanal@igalia.com>,
"Dan Carpenter" <dan.carpenter@linaro.org>,
"Kees Cook" <keescook@chromium.org>,
"Daniel Diaz" <daniel.diaz@linaro.org>,
"David Gow" <davidgow@google.com>,
"Arthur Grillo" <arthurgrillo@riseup.net>,
"Brendan Higgins" <brendan.higgins@linux.dev>,
"Naresh Kamboju" <naresh.kamboju@linaro.org>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Maxime Ripard" <mripard@kernel.org>,
"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
loongarch@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
kunit-dev@googlegroups.com, linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH 0/5] Add support for suppressing warning backtraces
Date: Sun, 10 Mar 2024 21:36:10 -0700 [thread overview]
Message-ID: <d24f147c-a304-4395-aefc-bed7490278b6@roeck-us.net> (raw)
In-Reply-To: <20240305184033.425294-1-linux@roeck-us.net>
On Tue, Mar 05, 2024 at 10:40:28AM -0800, Guenter Roeck wrote:
> Some unit tests intentionally trigger warning backtraces by passing bad
> parameters to kernel API functions. Such unit tests typically check the
> return value from such calls, not the existence of the warning backtrace.
>
> Such intentionally generated warning backtraces are neither desirable
> nor useful for a number of reasons.
> - They can result in overlooked real problems.
> - A warning that suddenly starts to show up in unit tests needs to be
> investigated and has to be marked to be ignored, for example by
> adjusting filter scripts. Such filters are ad-hoc because there is
> no real standard format for warnings. On top of that, such filter
> scripts would require constant maintenance.
>
> One option to address problem would be to add messages such as "expected
> warning backtraces start / end here" to the kernel log. However, that
> would again require filter scripts, it might result in missing real
> problematic warning backtraces triggered while the test is running, and
> the irrelevant backtrace(s) would still clog the kernel log.
>
> Solve the problem by providing a means to identify and suppress specific
> warning backtraces while executing test code. Support suppressing multiple
> backtraces while at the same time limiting changes to generic code to the
> absolute minimum. Architecture specific changes are kept at minimum by
> retaining function names only if both CONFIG_DEBUG_BUGVERBOSE and
> CONFIG_KUNIT are enabled.
>
> The first patch of the series introduces the necessary infrastructure.
> The second patch marks the warning message in drm_calc_scale() in the DRM
> subsystem as intentional where warranted. This patch is intended to serve
> as an example for the use of the functionality introduced with this series.
> The last three patches in the series introduce the necessary architecture
> specific changes for x86, arm64, and loongarch.
>
> This series is based on the RFC patch and subsequent discussion at
> https://patchwork.kernel.org/project/linux-kselftest/patch/02546e59-1afe-4b08-ba81-d94f3b691c9a@moroto.mountain/
> and offers a more comprehensive solution of the problem discussed there.
>
> Checkpatch note:
> Remaining checkpatch errors and warnings were deliberately ignored.
> Some are triggered by matching coding style or by comments interpreted
> as code, others by assembler macros which are disliked by checkpatch.
> Suggestions for improvements are welcome.
>
> Some questions:
>
> - Is the general approach promising ? If not, are there other possible
> solutions ?
> - Function pointers are only added to the __bug_table section if both
> CONFIG_KUNIT and CONFIG_DEBUG_BUGVERBOSE are enabled. This avoids image
> size increases if CONFIG_KUNIT=n. Downside is slightly more complex
> architecture specific assembler code. If function pointers were always
> added to the __bug_table section, vmlinux image size would increase by
> approximately 0.6-0.7%. Is the increased complexity in assembler code
> worth the reduced image size ? I think so, but I would like to hear
> other opinions.
> - There are additional possibilities associated with storing the bug
> function name in the __bug_table section. It could be independent of
> KUNIT, it could be a configuration flag, and/or it could be used to
> display the name of the offending function in BUG/WARN messages.
> Is any of those of interest ?
>
I am ready to send a full version of this series with support for
all affected architectures. I am undecided if I should send it now,
based on v6.8, and send v2 after rebasing it to v6.9-rc1, or if I
should just wait for v6.9-rc1.
I understand that some maintainers dislike getting new patch series
while the commit window is is open. On the ther side, I tested the
series thoroughly on top of v6.8-rc7, and initial v6.9 release candidates
may have their own problems. Given that, I tend to send the series now.
Any thoughts ? Unless there is strong negative feedback, I'll likely
do that in a day or two.
Thanks,
Guenter
prev parent reply other threads:[~2024-03-11 4:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-05 18:40 [RFC PATCH 0/5] Add support for suppressing warning backtraces Guenter Roeck
2024-03-05 18:40 ` [RFC PATCH 1/5] bug: Core " Guenter Roeck
2024-03-05 19:54 ` Kees Cook
2024-03-05 20:17 ` Guenter Roeck
2024-03-05 18:40 ` [RFC PATCH 2/5] drm: Suppress intentional warning backtraces in scaling unit tests Guenter Roeck
2024-03-05 18:40 ` [RFC PATCH 3/5] x86: Add support for suppressing warning tracebacks Guenter Roeck
2024-03-05 18:40 ` [RFC PATCH 4/5] arm64: " Guenter Roeck
2024-03-05 18:40 ` [RFC PATCH 5/5] loongarch: " Guenter Roeck
2024-03-06 18:24 ` [RFC PATCH 0/5] Add support for suppressing warning backtraces Daniel Díaz
2024-03-06 18:57 ` Guenter Roeck
2024-03-11 4:36 ` Guenter Roeck [this message]
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