The current section 'If something goes wrong' makes a number of suggestions
for debugging, bug hunting and reporting issues, which are quite briefly
described in that section.
However, the suggestions are also well covered in other kernel
documentation or sometimes simply outdated. Here, each suggestion in that
section is summarized, and then followed with its assessment, and the
derived action for each suggestion:
- use MAINTAINERS and mailing list: covered in 'Reporting issues',
summarized in the short guide, detailed in its further section.
Reporting issues even provides some specific examples that guides
readers well through the needed steps. Refer to 'Reporting issues'.
- contact Linus Torvalds: probably outdated as currently described.
nevertheless covered in 'Reporting issues'. Reporting issues points out
to contact the relevant kernel maintainers first, and after some
patience and failed attempts with those maintainers, contacting Linus
Torvalds might be okay. Refer to 'Reporting issues'.
- tell what kernel, how to duplicate, the setup, if the problem is new
or old and when did you notice: covered in 'Reporting issues',
especially in Step-by-step guide how to report issues to the kernel
maintainers. Refer to 'Reporting issues'.
- duplicate kernel bug reports exactly: covered in 'Reporting issues',
especially in Write and send the report. Refer to 'Reporting issues'.
- read 'Bug hunting': keep this reference. Refer to 'Bug hunting'.
- compile the kernel with CONFIG_KALLSYMS: covered in 'Reporting issues',
especially in Decode failure messages. Refer to 'Reporting issues'.
- alternatively, use ksymoops: ksymoops at the mentioned URL seems not to
be maintained anymore. It was released roughly once a year until
version 2.4.11 in 2005, but has not seen a new release since then. The
information in ./scripts/ksymoops/README is from 1999, and does not
give more insight on its actual maintenance state either. Ksymoops is
mentioned as system utility in changes.rst, but also not recommended
there. Drop the explanation on using ksymoops.
- alternatively, lookup dump manually with the EIP and nm to determine
the function in which the kernel crashes: this method seems already a
quite advanced and low-level debugging method. Even all the further
references on bug hunting and debugging do not mention it. Drop this
alternative method and limit mentioning methods explained in the other
existing kernel documentation.
- read 'Reporting issues': keep this reference.
Refer to 'Reporting issues'.
- use gdb for debugging: some specific details, e.g., edit
arch/x86/Makefile, are probably outdated or limited to one (historic
important) setup. Using gdb is covered in 'Bug hunting', 'Debugging
kernel and modules via gdb' and 'Using kgdb, kdb and the kernel
debugger internals'. Refer to those three documents.
Overall, it is sufficient to refer to reporting-issues.rst,
bug-hunting.rst, gdb-kernel-debugging.rst and kgdb.rst and this way cover
the existing suggestions.
'Reporting issues' is quite new and probably up to date. 'Bug hunting',
'Debugging kernel and modules via gdb' and 'Using kgdb, kdb and the kernel
debugger internals' might need some revisit and update, but they are
generally in an acceptable state for referring to them.
Replace the existing suggestions by reference to other existing kernel
documentation covering those suggestions---partly even nicely summarized
and then explained in greater detail.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220720041325.15693-3-lukas.bulwahn@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Running a.out user programs with the latest kernel release is a very rare
and uncommon use case nowadays. The support of a.out user programs is only
remaining for the alpha architecture and is not defined and activated in
the architecture's Kconfig (so even the activation of this support requires
to modify the Kconfig file and not just kernel build configuration).
The discussion on a.out support in 2019 (see Link) shows that the support
of a.out user programs is just remaining for a special corner case from
some (alpha architecture) users.
There is no need to point out and mention this special feature to the
general audience of kernel users. Delete the reference to this historic and
special feature.
Link: https://lore.kernel.org/all/CAHk-=wgt7M6yA5BJCJo0nF22WgPJnN8CvViL9CAJmd+S+Civ6w@mail.gmail.com/
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20220720041325.15693-2-lukas.bulwahn@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Correct all uses of "it's" that are meant to be possessive "its".
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20220801025207.29971-1-rdunlap@infradead.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
On some distros with coarse-grained packaging policy, dvipng is
installed along with latex. In such cases, math rendering will
use imgmath by default. It is possible to override the choice by
specifying the option string of "-D html_math_renderer='mathjax'"
to sphinx-build (Sphinx >= 1.8).
To provide developers an easier-to-use knob, add code for an env
variable "SPHINX_IMGMATH" which overrides the automatic choice
of math renderer for html docs.
SPHINX_IMGMATH=yes : Load imgmath even if dvipng is not found
SPHINX_IMGMATH=no : Don't load imgmath (fall back to mathjax)
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/5a582b2b-d51c-a062-36b2-19479cf68fab@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Currently, math expressions using the "math::" directive or
the ":math:" role of Sphinx need the imgmath extension for proper
rendering in html and epub builds.
imgmath requires dvipng (and latex).
Otherwise, "make htmldocs" will complain of missing commands.
As a matter of fact, the mathjax extension is loaded by default since
Sphinx v1.8 and it is good enough for html docs without any dependency
on texlive packages.
Stop loading the imgmath extension for html docs unless requirements
for imgmath are met.
To find out whether required commands are available, add a helper
find_command(), which is a wrapper of shutil.which().
For epub docs, keep the same behavior of always loading imgmath.
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Acked-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lore.kernel.org/r/a6a877fc-dc93-2bda-a6d3-37001d99942a@gmail.com
[jc: Took out the writing of the math_renderer decision]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
* update to commit 163ba35ff3 ("doc: use KCFLAGS instead of
EXTRA_CFLAGS to pass flags from command line")
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Reviewed-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/Ywli7VfhQVPHKiGw@bobwxc.mipc
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Add missing update for the documentation bit of some scheduler knob.
The knobs have been moved to /debug/sched/ location (with adjusted names).
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Alex Shi <alexs@kernel.org>
Tested-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/20220816121907.841-1-lukasz.luba@arm.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The English version of IRQ has been refactored and
the new document (not called that anymore) has been
moved to core-api/irq, which has been translated
into Chinese. oops-tracing is pretty much the same,
let's remove them.
Signed-off-by: Yanteng Si <siyanteng@loongson.cn>
Reviewed-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/7dc43c33ea7e2edf668070b203dce83b285f2cdb.1661431365.git.siyanteng@loongson.cn
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
The description of s_lastcheck_hi, s_first_error_time_hi, and
s_last_error_time_hi fields refer to themselves, while these means
referring to upper 8 bits (byte) of corresponding fields (s_lastcheck,
s_first_error_time, and s_last_error_time). Correct the mistake.
Signed-off-by: JunChao Sun <sunjunchao2870@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20220815125233.2040-1-sunjunchao2870@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
According to the implementation of xfs_trans_roll(), it calls
xfs_trans_reserve(), which reserves not only log space, but also
free disk blocks. In short, the "transaction stuff". So change
xfs_log_reserve() to xfs_trans_reserve().
Besides, fix several typo issues.
Signed-off-by: Zhao Mengmeng <zhaomengmeng@kylinos.cn>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20220823013653.203469-1-zhaomzhao@126.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
* Add back still referenced labels in submitting-patches.rst and
email-clients.rst.
* Fix a typo.
Fixes: fdb34b18b959 ("docs/zh_CN: Update zh_CN/process/submitting-patches.rst to 5.19")
Fixes: d7aeaebb920f ("docs/zh_CN: Update zh_CN/process/email-clients.rst to 5.19")
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Link: https://lore.kernel.org/r/Yv7i1tYMvK9J/NHj@bobwxc.mipc
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Merge series from Zhang Qilong <zhangqilong3@huawei.com>:
The pm_runtime_enable will increase power disable depth. Thus
a pairing decrement is needed on the error handling path to
keep it balanced. We fix it by moving pm_runtime_enable to the
endding of probe.
If a page is partially read, and then the splice system call is run
against the ring buffer, it will always fail to read, no matter how much
is in the ring buffer. That's because the code path for a partial read of
the page does will fail if the "full" flag is set.
The splice system call wants full pages, so if the read of the ring buffer
is not yet full, it should return zero, and the splice will block. But if
a previous read was done, where the beginning has been consumed, it should
still be given to the splice caller if the rest of the page has been
written to.
This caused the splice command to never consume data in this scenario, and
let the ring buffer just fill up and lose events.
Link: https://lkml.kernel.org/r/20220927144317.46be6b80@gandalf.local.home
Cc: stable@vger.kernel.org
Fixes: 8789a9e7df ("ring-buffer: read page interface")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
When executing following commands like what document said, but the log
"#### all functions enabled ####" was not shown as expect:
1. Set a 'mod' filter:
$ echo 'write*:mod:ext3' > /sys/kernel/tracing/set_ftrace_filter
2. Invert above filter:
$ echo '!write*:mod:ext3' >> /sys/kernel/tracing/set_ftrace_filter
3. Read the file:
$ cat /sys/kernel/tracing/set_ftrace_filter
By some debugging, I found that flag FTRACE_HASH_FL_MOD was not unset
after inversion like above step 2 and then result of ftrace_hash_empty()
is incorrect.
Link: https://lkml.kernel.org/r/20220926152008.2239274-1-zhengyejian1@huawei.com
Cc: <mingo@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 8c08f0d5c6 ("ftrace: Have cached module filters be an active filter")
Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The event dir will alloc failed when event name no set, using the
command:
"echo "e:esys/ syscalls/sys_enter_openat file=\$filename:string"
>> dynamic_events"
It seems that dir name="syscalls/sys_enter_openat" is not allowed
in debugfs. So just use the "sys_enter_openat" as the event name.
Link: https://lkml.kernel.org/r/1664028814-45923-1-git-send-email-chentao.kernel@linux.alibaba.com
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Cc: Linyu Yuan <quic_linyyuan@quicinc.com>
Cc: Tao Chen <chentao.kernel@linux.alibaba.com
Cc: stable@vger.kernel.org
Fixes: 95c104c378 ("tracing: Auto generate event name when creating a group of events")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Tao Chen <chentao.kernel@linux.alibaba.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
An unused macro reported by [-Wunused-macros].
This macro is used to access the sp in pt_regs because at that time
x86_32 can only get sp by kernel_stack_pointer(regs).
'3c88c692c2 ("x86/stackframe/32: Provide consistent pt_regs")'
This commit have unified the pt_regs and from them we can get sp from
pt_regs with regs->sp easily. Nowhere is using this macro anymore.
Refrencing pt_regs directly is more clear. Remove this macro for
code cleaning.
Link: https://lkml.kernel.org/r/20220924072629.104759-1-chenzhongjin@huawei.com
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The trace of "struct task_struct" was no longer used since
commit 345ddcc882 ("ftrace: Have set_ftrace_pid use the
bitmap like events do"), and the functions about flags for
current->trace is useless, so remove them.
Link: https://lkml.kernel.org/r/20220923090012.505990-1-cuigaosheng1@huawei.com
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
It was found that some tracing functions in kernel/trace/trace.c acquire
an arch_spinlock_t with preemption and irqs enabled. An example is the
tracing_saved_cmdlines_size_read() function which intermittently causes
a "BUG: using smp_processor_id() in preemptible" warning when the LTP
read_all_proc test is run.
That can be problematic in case preemption happens after acquiring the
lock. Add the necessary preemption or interrupt disabling code in the
appropriate places before acquiring an arch_spinlock_t.
The convention here is to disable preemption for trace_cmdline_lock and
interupt for max_lock.
Link: https://lkml.kernel.org/r/20220922145622.1744826-1-longman@redhat.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: stable@vger.kernel.org
Fixes: a35873a099 ("tracing: Add conditional snapshot")
Fixes: 939c7a4f04 ("tracing: Introduce saved_cmdlines_size file")
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Drop the requirement for system-wide kernel UAPI headers to provide full
struct btf_enum64 definition. This is an unexpected requirement that
slipped in libbpf 1.0 and put unnecessary pressure ([0]) on users to have
a bleeding-edge kernel UAPI header from unreleased Linux 6.0.
To achieve this, we forward declare struct btf_enum64. But that's not
enough as there is btf_enum64_value() helper that expects to know the
layout of struct btf_enum64. So we get a bit creative with
reinterpreting memory layout as array of __u32 and accesing lo32/hi32
fields as array elements. Alternative way would be to have a local
pointer variable for anonymous struct with exactly the same layout as
struct btf_enum64, but that gets us into C++ compiler errors complaining
about invalid type casts. So play it safe, if ugly.
[0] Closes: https://github.com/libbpf/libbpf/issues/562
Fixes: d90ec262b3 ("libbpf: Add enum64 support for btf_dump")
Reported-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Toke Høiland-Jørgensen <toke@toke.dk>
Link: https://lore.kernel.org/bpf/20220927042940.147185-1-andrii@kernel.org
- Use drm_display_info.is_hdmi instead of drm_detect_hdmi_monitor()
for efficiency.
Fixup
- Correct return type of mixer_mode_valid and hdmi_mode_valid functions.
This was reported by Dan Carpenter, https://github.com/ClangBuiltLinux/linux/issues/1703
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Merge tag 'exynos-drm-next-for-v6.1' of git://git.kernel.org/pub/scm/linux/kernel/git/daeinki/drm-exynos into drm-next
Cleanup
- Use drm_display_info.is_hdmi instead of drm_detect_hdmi_monitor()
for efficiency.
Fixup
- Correct return type of mixer_mode_valid and hdmi_mode_valid functions.
This was reported by Dan Carpenter, https://github.com/ClangBuiltLinux/linux/issues/1703
Signed-off-by: Dave Airlie <airlied@redhat.com>
From: Inki Dae <inki.dae@samsung.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220926020723.270065-1-inki.dae@samsung.com
In the v2022.10 reference design, the seg registers are going to be
changed, resulting in a required change to the memory map in Linux.
A small 4M reservation is made at the end of 32-bit DDR to provide some
memory for the HSS to use, so that it can cache its payload.bin between
reboots of a specific context.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
For the v2022.09 release of the reference design, the fic3 clock rate
been reduced from 62.5 MHz to 50 MHz as it allows timing to be closed
significantly more quickly by customers who chose to build the
reference design themselves.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
When users try to add onto the reference design, they find that the
current addresses that peripherals connected to Fabric InterConnect
(FIC) 3 use are restrictive. For the v2022.09 reference design, the
peripherals have been shifted down, leaving more contiguous address
space for their custom IP/peripherals.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
For the v2022.09 reference design the PCI root port's data region has
been moved to FIC1 from FIC0. This is a shorter path, allowing for
higher clock rates and improved through-put. As a result, the address at
which the PCIe's data region appears to the core complex has changed.
The config region's address is unchanged.
As FIC0 is no longer used, its clock can be removed too.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
In today's edition of moving things around:
The PCIe root port on PolarFire SoC is more part of the FPGA than of
the Core Complex. It is located on the other side of the chip and,
apart from its interrupts, most of its configuration is determined
by the FPGA bitstream rather. This includes:
- address translation in both directions
- the addresses at which the config and data regions appear to the
core complex
- the clocks used by the AXI bus
- the plic interrupt used
Moving the PCIe node to the -fabric.dtsi makes it clearer than a
singular configuration for root port is not correct & allows the
base SoC dtsi to be more easily included.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
The recently removed, accidentally included, "matr0" property was used
in place of a dma-ranges property. The PCI controller is non-functional
with mainline Linux in the v2022.02 or later reference designs and has
not worked without configuration of address-translation since v2021.08.
Add the address translation that will be used by the v2022.09 reference
design & update the compatible used by the dts. Since this change is not
backwards compatible, update the compatible to denote this, jumping over
v2022.09 directly to v2022.10.
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
The icicle kit reference design's v2022.09 release made some changes
to the memory map - including adding the ability to read the fabric
clock controllers via the system controller bus & making the PCI
controller work with upstream Linux.
While the PCI was not working in the v2022.03 design, so nothing is
broken there in terms of backwards compatibility, the fabric clocks
used in the v2022.03 design were chosen by the individual run of the
synthesis tool. In the v2022.09 reference design, the clocks are fixed
to use the "north west" fabric Clock Conditioning Circuitry.
In the v2022.10 release, the memory map on the DDR side is also
changing, so to avoid making a breaking change here twice, jump over the
v2022.09 release and straight to the v2022.10 one.
Make use of a new compatible to denote that v2022.{09,10} reference
design releases are not backwards compatible.
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
blkg_conf_prep just creates a new blkg structure, there is no real
need to update the lookup hint which should only be done on a
successful lookup in the I/O path.
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20220927065425.257876-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If attempting to perform a GT reset takes long than 5 seconds (including
resetting the display for gen3/4), then we declare all hope lost and
discard all user work and wedge the device to prevent further
misbehaviour. 5 seconds is too short a time for such drastic action, as
we may be stuck on other timeouts and watchdogs. If we allow a little
bit longer before hitting the big red button, we should at the very
least capture other hung task indicators pointing towards the reason why
the reset was hanging; and allow more marginal cases the extra headroom
to complete the reset without further collateral damage.
Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/6448
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220916204823.1897089-1-ashutosh.dixit@intel.com
Extend the existing test cases to test the conversion from XRGB8888 to
XRGB2101010.
In order to be able to call drm_fb_xrgb8888_to_xrgb2101010() when
compiling CONFIG_DRM_KMS_HELPER as a module export the symbol.
Tested-by: Maíra Canal <mairacanal@riseup.net>
Reviewed-by: David Gow <davidgow@google.com>
Acked-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: José Expósito <jose.exposito89@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220926080837.65734-3-jose.exposito89@gmail.com
