The Arm NI-700 Network-on-Chip Interconnect has a relatively
straightforward design with a hierarchy of voltage, power, and clock
domains, where each clock domain then contains a number of interface
units and a PMU which can monitor events thereon. As such, it begets a
relatively straightforward driver to interface those PMUs with perf.
Even more so than with arm-cmn, users will require detailed knowledge of
the wider system topology in order to meaningfully analyse anything,
since the interconnect itself cannot know what lies beyond the boundary
of each inscrutably-numbered interface. Given that, for now they are
also expected to refer to the NI-700 documentation for the relevant
event IDs to provide as well. An identifier is implemented so we can
come back and add jevents if anyone really wants to.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/9933058d0ab8138c78a61cd6852ea5d5ff48e393.1725470837.git.robin.murphy@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
Commit ed5cc702d3 ("block: Add config option to not allow writing to mounted
devices") added a Kconfig option along with a kernel command-line tuning to
control writes to mounted block devices, as a means to deal with fuzzers like
Syzkaller, that provokes kernel crashes by directly writing on block devices
bypassing the filesystem (so the FS has no awareness and cannot cope with that).
The patch just missed adding such kernel command-line option to the kernel
documentation, so let's fix that.
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240828145045.309835-1-gpiccoli@igalia.com
Add support for the Extron DA HD 4K Plus series of 4K HDMI
Distrubution Amplifiers (aka HDMI Splitters).
These devices support CEC and this driver adds support for the
CEC protocol for both the input and all outputs (2, 4 or 6 outputs,
depending on the model).
It also exports the EDID from the outputs and allows reading and
setting the EDID of the input.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Merge "hwmon fixes for v6.11-rc7" into review-hans to bring in
commit a54da9df75 ("hwmon: (hp-wmi-sensors) Check if WMI event
data exists").
This is a dependency for a set of WMI event data refactoring changes.
Add an on-by-default module param, enable_virt_at_load, to let userspace
force virtualization to be enabled in hardware when KVM is initialized,
i.e. just before /dev/kvm is exposed to userspace. Enabling virtualization
during KVM initialization allows userspace to avoid the additional latency
when creating/destroying the first/last VM (or more specifically, on the
0=>1 and 1=>0 edges of creation/destruction).
Now that KVM uses the cpuhp framework to do per-CPU enabling, the latency
could be non-trivial as the cpuhup bringup/teardown is serialized across
CPUs, e.g. the latency could be problematic for use case that need to spin
up VMs quickly.
Prior to commit 10474ae894 ("KVM: Activate Virtualization On Demand"),
KVM _unconditionally_ enabled virtualization during load, i.e. there's no
fundamental reason KVM needs to dynamically toggle virtualization. These
days, the only known argument for not enabling virtualization is to allow
KVM to be autoloaded without blocking other out-of-tree hypervisors, and
such use cases can simply change the module param, e.g. via command line.
Note, the aforementioned commit also mentioned that enabling SVM (AMD's
virtualization extensions) can result in "using invalid TLB entries".
It's not clear whether the changelog was referring to a KVM bug, a CPU
bug, or something else entirely. Regardless, leaving virtualization off
by default is not a robust "fix", as any protection provided is lost the
instant userspace creates the first VM.
Reviewed-by: Chao Gao <chao.gao@intel.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20240830043600.127750-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The ability to observe the demotion and promotion decisions made by the
kernel on a per-cgroup basis is important for monitoring and tuning
containerized workloads on machines equipped with tiered memory.
Different containers in the system may experience drastically different
memory tiering actions that cannot be distinguished from the global
counters alone.
For example, a container running a workload that has a much hotter memory
accesses will likely see more promotions and fewer demotions, potentially
depriving a colocated container of top tier memory to such an extent that
its performance degrades unacceptably.
For another example, some containers may exhibit longer periods between
data reuse, causing much more numa_hint_faults than numa_pages_migrated.
In this case, tuning hot_threshold_ms may be appropriate, but the signal
can easily be lost if only global counters are available.
In the long term, we hope to introduce per-cgroup control of promotion and
demotion actions to implement memory placement policies in tiering.
This patch set adds seven counters to memory.stat in a cgroup:
numa_pages_migrated, numa_pte_updates, numa_hint_faults, pgdemote_kswapd,
pgdemote_khugepaged, pgdemote_direct and pgpromote_success. pgdemote_*
and pgpromote_success are also available in memory.numa_stat.
count_memcg_events_mm() is added to count multiple event occurrences at
once, and get_mem_cgroup_from_folio() is added because we need to get a
reference to the memcg of a folio before it's migrated to track
numa_pages_migrated. The accounting of PGDEMOTE_* is moved to
shrink_inactive_list() before being changed to per-cgroup.
[kaiyang2@cs.cmu.edu: add documentation of the memcg counters in cgroup-v2.rst]
Link: https://lkml.kernel.org/r/20240814235122.252309-1-kaiyang2@cs.cmu.edu
Link: https://lkml.kernel.org/r/20240814174227.30639-1-kaiyang2@cs.cmu.edu
Signed-off-by: Kaiyang Zhao <kaiyang2@cs.cmu.edu>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The pressure_level in memcg v1 provides memory pressure notifications to
the user space. At the moment it provides notifications for three levels
of memory pressure i.e. low, medium and critical, which are defined based
on internal memory reclaim implementation details. More specifically the
ratio of scanned and reclaimed pages during a memory reclaim. However
this is not robust as there are workloads with mostly unreclaimable user
memory or kernel memory.
For v2, the users can use PSI for memory pressure status of the system or
the cgroup. Let's start the deprecation process for pressure_level and
add warnings to gather the info on how the current users are using this
interface and how they can be used to PSI.
Link: https://lkml.kernel.org/r/20240814220021.3208384-5-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
The oom_control provides functionality to disable memcg oom-killer,
notifications on oom-kill and reading the stats regarding oom-kills. This
interface was mainly introduced to provide functionality for userspace
oom-killers. However it is not robust enough and only supports OOM
handling in the page fault path.
For v2, the users can use the combination of memory.events notifications,
memory.high and PSI to provide userspace OOM-killing functionality.
Actually LMKD in Android and OOMd in systemd and Meta infrastructure
already use PSI in combination with other stats to implement userspace
OOM-killing.
Let's start the deprecation process for v1 and gather the info on how the
current users are using this interface and work on providing a more robust
functionality in v2.
Link: https://lkml.kernel.org/r/20240814220021.3208384-4-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Memcg v1 provides soft limit functionality for the best effort memory
sharing between multiple workloads on a system. It is usually triggered
through kswapd and at the moment does not reclaim kernel memory.
Memcg v2 provides more straightforward best effort (memory.low) and hard
protection (memory.min) functionalities. Let's initiate the deprecation
of soft limit from v1 and gather if v2 needs something more to move the
existing v1 users to v2 regarding soft limit.
Link: https://lkml.kernel.org/r/20240814220021.3208384-3-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "memcg: initiate deprecation of v1 features", v2.
Start the deprecation process of the memcg v1 features which we discussed
during LSFMMBPF 2024 [1]. For now add the warnings to collect the
information on how the current users are using these features. Next we
will work on providing better alternatives in v2 (if needed) and fully
deprecate these features.
Link: https://lwn.net/Articles/974575 [1]
This patch (of 4):
Memcg v1 provides opt-in TCP memory accounting feature. However it is
mostly unused due to its performance impact on the network traffic. In
v2, the TCP memory is accounted in the regular memory usage and is
transparent to the users but they can observe the TCP memory usage through
memcg stats.
Let's initiate the deprecation process of memcg v1's tcp accounting
functionality and add warnings to gather if there are any users and if
there are, collect how they are using it and plan to provide them better
alternative in v2.
Link: https://lkml.kernel.org/r/20240814220021.3208384-1-shakeel.butt@linux.dev
Link: https://lkml.kernel.org/r/20240814220021.3208384-2-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Patch series "mm, memcg: cg2 memory{.swap,}.peak write handlers", v7.
This patch (of 2):
Other mechanisms for querying the peak memory usage of either a process or
v1 memory cgroup allow for resetting the high watermark. Restore parity
with those mechanisms, but with a less racy API.
For example:
- Any write to memory.max_usage_in_bytes in a cgroup v1 mount resets
the high watermark.
- writing "5" to the clear_refs pseudo-file in a processes's proc
directory resets the peak RSS.
This change is an evolution of a previous patch, which mostly copied the
cgroup v1 behavior, however, there were concerns about races/ownership
issues with a global reset, so instead this change makes the reset
filedescriptor-local.
Writing any non-empty string to the memory.peak and memory.swap.peak
pseudo-files reset the high watermark to the current usage for subsequent
reads through that same FD.
Notably, following Johannes's suggestion, this implementation moves the
O(FDs that have written) behavior onto the FD write(2) path. Instead, on
the page-allocation path, we simply add one additional watermark to
conditionally bump per-hierarchy level in the page-counter.
Additionally, this takes Longman's suggestion of nesting the
page-charging-path checks for the two watermarks to reduce the number of
common-case comparisons.
This behavior is particularly useful for work scheduling systems that need
to track memory usage of worker processes/cgroups per-work-item. Since
memory can't be squeezed like CPU can (the OOM-killer has opinions), these
systems need to track the peak memory usage to compute system/container
fullness when binpacking workitems.
Most notably, Vimeo's use-case involves a system that's doing global
binpacking across many Kubernetes pods/containers, and while we can use
PSI for some local decisions about overload, we strive to avoid packing
workloads too tightly in the first place. To facilitate this, we track
the peak memory usage. However, since we run with long-lived workers (to
amortize startup costs) we need a way to track the high watermark while a
work-item is executing. Polling runs the risk of missing short spikes
that last for timescales below the polling interval, and peak memory
tracking at the cgroup level is otherwise perfect for this use-case.
As this data is used to ensure that binpacked work ends up with sufficient
headroom, this use-case mostly avoids the inaccuracies surrounding
reclaimable memory.
Link: https://lkml.kernel.org/r/20240730231304.761942-1-davidf@vimeo.com
Link: https://lkml.kernel.org/r/20240729143743.34236-1-davidf@vimeo.com
Link: https://lkml.kernel.org/r/20240729143743.34236-2-davidf@vimeo.com
Signed-off-by: David Finkel <davidf@vimeo.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Waiman Long <longman@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Zefan Li <lizefan.x@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Currently users can get the Root Ports supported by the PCIe PMU by
"bus" sysfs attributes which indicates the PCIe bus number where
Root Ports are located. This maybe insufficient since Root Ports
supported by different PCIe PMUs may be located on the same PCIe bus.
So export the BDF range the Root Ports additionally.
Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240829090332.28756-4-yangyicong@huawei.com
Signed-off-by: Will Deacon <will@kernel.org>
Rewrite the short document on bisecting kernel bugs. The new text
improves .config handling, brings a mention of 'git bisect skip', and
explains what to do after the bisection finished -- including trying a
revert to verify the result. The rewrite at the same time removes the
unrelated and outdated section on 'Devices not appearing' and replaces
some sentences about bug reporting with a pointer to the document
covering that topic in detail.
This overall brings the approach close to the one in the recently added
text Documentation/admin-guide/verify-bugs-and-bisect-regressions.rst.
As those two texts serve a similar purpose for different audiences,
mention that document in the head of this one and outline when the
other might be the better one to follow.
Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Reviewed-by: Petr Tesarik <petr@tesarici.cz>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/74dc0137dcc3e2c05648e885a7bc31ffd39a0890.1724312119.git.linux@leemhuis.info
For the MAC based integrity operation, the integrity key size (i.e.
key_mac_size) is currently set to the digest size of the used digest.
For wrapped key HMAC algorithms, the key size is independent of the
cryptographic key size. So there is no known size of the mac key in
such cases. The desired key size can optionally be specified as argument
when the dm-crypt device is configured via 'integrity_key_size:%u'.
If no integrity_key_size argument is specified, the mac key size
is still set to the digest size, as before.
Increase version number to 1.28.0 so that support for the new
argument can be detected by user space (i.e. cryptsetup).
Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Add a new dmsetup message called config, which will return
useful configuration information for the vdo volume and
the uds index associated with it. The output is a YAML
string, and contains a version number to allow future
additions to the content.
Signed-off-by: Bruce Johnston <bjohnsto@redhat.com>
Signed-off-by: Matthew Sakai <msakai@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
The comment in cgroup_file_write is missing some interfaces, such as
'cgroup.threads'. All delegatable files are listed in
'/sys/kernel/cgroup/delegate', so update the comment in cgroup_file_write.
Besides, add a statement that files outside the namespace shouldn't be
visible from inside the delegated namespace.
tj: Reflowed text for consistency.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Allow boot instances to use memory reserved by the reserve_mem boot
option.
reserve_mem=12M:4096:trace trace_instance=boot_mapped@trace
The above will allocate 12 megs with 4096 alignment and label it "trace".
The second parameter will create a "boot_mapped" instance and use the
memory reserved and labeled as "trace" as the memory for the ring buffer.
That will create an instance called "boot_mapped":
/sys/kernel/tracing/instances/boot_mapped
Note, because the ring buffer is using a defined memory ranged, it will
act just like a memory mapped ring buffer. It will not have a snapshot
buffer, as it can't swap out the buffer. The snapshot files as well as any
tracers that uses a snapshot will not be present in the boot_mapped
instance.
Also note that reserve_mem is not reliable in acquiring the same physical
memory at each soft reboot. It is possible that KALSR could map the kernel
at the previous boot memory location forcing the reserve_mem to return a
different memory location. In this case, the previous ring buffer will be
lost.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Link: https://lore.kernel.org/20240815082811.669f7d8c@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
The "reserve_mem" kernel command line parameter has been pulled into
v6.11. Merge the latest -rc3 to allow the persistent ring buffer memory to
be able to be mapped at the address specified by the "reserve_mem" command
line parameter.
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
During CSD-lock stalls, the additional information output by RCU CPU
stall warnings is usually redundant, flooding the console for not good
reason. However, this has been the way things work for a few years.
This commit therefore adds an rcutree.csd_lock_suppress_rcu_stall kernel
boot parameter that causes RCU CPU stall warnings to be abbreviated to
a single line when there is at least one CPU that has been stuck waiting
for CSD lock for more than five seconds.
To make this abbreviated message happen with decent probability:
tools/testing/selftests/rcutorture/bin/kvm.sh --allcpus --duration 8 \
--configs "2*TREE01" --kconfig "CONFIG_CSD_LOCK_WAIT_DEBUG=y" \
--bootargs "csdlock_debug=1 rcutorture.stall_cpu=200 \
rcutorture.stall_cpu_holdoff=120 rcutorture.stall_cpu_irqsoff=1 \
rcutree.csd_lock_suppress_rcu_stall=1 \
rcupdate.rcu_exp_cpu_stall_timeout=5000" --trust-make
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
The call_rcu_tasks_rude() and rcu_barrier_tasks_rude() APIs are no longer.
This commit therefore removes them from the documentation.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
This commit adds an stall_cpu_repeat kernel, which is also the
rcutorture.stall_cpu_repeat boot parameter, to test repeated CPU stalls.
Note that only the first stall will pay attention to the stall_cpu_irqsoff
module parameter. For the second and subsequent stalls, interrupts will
be enabled. This is helpful when testing the interaction between RCU
CPU stall warnings and CSD-lock stall warnings.
Reported-by: Rik van Riel <riel@surriel.com>
Signed-off-by: "Paul E. McKenney" <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay <neeraj.upadhyay@kernel.org>
Properly document the function of the mgb4 output "frame_rate" sysfs
parameter and update the default DV timings values according to the latest
code changes.
Signed-off-by: Martin Tůma <martin.tuma@digiteqautomotive.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
While building kernel documention using make htmldocs command, I was
getting unexpected indentation error. Single description was given for
two module parameters with wrong indentation. So, I corrected the
indentation of both parameters and the description.
Signed-off-by: Shibu kumar <shibukumar.bit@gmail.com>
Signed-off-by: Daniel Yang <danielyangkang@gmail.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: 0d815e3400 ("dm-crypt: limit the size of encryption requests")
The rkisp1 driver stores ISP configuration parameters in the fixed
rkisp1_params_cfg structure. As the members of the structure are part of
the userspace API, the structure layout is immutable and cannot be
extended further. Introducing new parameters or modifying the existing
ones would change the buffer layout and cause breakages in existing
applications.
The allow for future extensions to the ISP parameters, introduce a new
extensible parameters format, with a new format 4CC. Document usage of
the new format in the rkisp1 admin guide.
Signed-off-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
The vivid driver supports media controller support for quite a long
time now, so drop that from the list.
Since commit 4c4dacb052 ("media: vivid: loopback based on
'Connected To' controls") making EDID changes causes correct signaling
to happen, but what is still missing is the 100 ms delay required before
signaling that there is an HPD. Modify this TODO item accordingly.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Setting encryption as required in security flags was broken.
For example (to require all mounts to be encrypted by setting):
"echo 0x400c5 > /proc/fs/cifs/SecurityFlags"
Would return "Invalid argument" and log "Unsupported security flags"
This patch fixes that (e.g. allowing overriding the default for
SecurityFlags 0x00c5, including 0x40000 to require seal, ie
SMB3.1.1 encryption) so now that works and forces encryption
on subsequent mounts.
Acked-by: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
The workqueue.panic_on_stall kernel parameter was added in commit
073107b39e ("workqueue: add cmdline parameter workqueue.panic_on_stall")
but not listed in the kernel-parameters doc. Add it there.
Signed-off-by: Sangmoon Kim <sangmoon.kim@samsung.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The kernel sleep profile is no longer working due to a recursive locking
bug introduced by commit 42a20f86dc ("sched: Add wrapper for get_wchan()
to keep task blocked")
Booting with the 'profile=sleep' kernel command line option added or
executing
# echo -n sleep > /sys/kernel/profiling
after boot causes the system to lock up.
Lockdep reports
kthreadd/3 is trying to acquire lock:
ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: get_wchan+0x32/0x70
but task is already holding lock:
ffff93ac82e08d58 (&p->pi_lock){....}-{2:2}, at: try_to_wake_up+0x53/0x370
with the call trace being
lock_acquire+0xc8/0x2f0
get_wchan+0x32/0x70
__update_stats_enqueue_sleeper+0x151/0x430
enqueue_entity+0x4b0/0x520
enqueue_task_fair+0x92/0x6b0
ttwu_do_activate+0x73/0x140
try_to_wake_up+0x213/0x370
swake_up_locked+0x20/0x50
complete+0x2f/0x40
kthread+0xfb/0x180
However, since nobody noticed this regression for more than two years,
let's remove 'profile=sleep' support based on the assumption that nobody
needs this functionality.
Fixes: 42a20f86dc ("sched: Add wrapper for get_wchan() to keep task blocked")
Cc: stable@vger.kernel.org # v5.16+
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cgroup subsystem state (CSS) is an abstraction in the cgroup layer to
help manage different structures in various cgroup subsystems by being
an embedded element inside a larger structure like cpuset or mem_cgroup.
The /proc/cgroups file shows the number of cgroups for each of the
subsystems. With cgroup v1, the number of CSSes is the same as the
number of cgroups. That is not the case anymore with cgroup v2. The
/proc/cgroups file cannot show the actual number of CSSes for the
subsystems that are bound to cgroup v2.
So if a v2 cgroup subsystem is leaking cgroups (usually memory cgroup),
we can't tell by looking at /proc/cgroups which cgroup subsystems may
be responsible.
As cgroup v2 had deprecated the use of /proc/cgroups, the hierarchical
cgroup.stat file is now being extended to show the number of live and
dying CSSes associated with all the non-inhibited cgroup subsystems that
have been bound to cgroup v2. The number includes CSSes in the current
cgroup as well as in all the descendants underneath it. This will help
us pinpoint which subsystems are responsible for the increasing number
of dying (nr_dying_descendants) cgroups.
The CSSes dying counts are stored in the cgroup structure itself
instead of inside the CSS as suggested by Johannes. This will allow
us to accurately track dying counts of cgroup subsystems that have
recently been disabled in a cgroup. It is now possible that a zero
subsystem number is coupled with a non-zero dying subsystem number.
The cgroup-v2.rst file is updated to discuss this new behavior.
With this patch applied, a sample output from root cgroup.stat file
was shown below.
nr_descendants 56
nr_subsys_cpuset 1
nr_subsys_cpu 43
nr_subsys_io 43
nr_subsys_memory 56
nr_subsys_perf_event 57
nr_subsys_hugetlb 1
nr_subsys_pids 56
nr_subsys_rdma 1
nr_subsys_misc 1
nr_dying_descendants 30
nr_dying_subsys_cpuset 0
nr_dying_subsys_cpu 0
nr_dying_subsys_io 0
nr_dying_subsys_memory 30
nr_dying_subsys_perf_event 0
nr_dying_subsys_hugetlb 0
nr_dying_subsys_pids 0
nr_dying_subsys_rdma 0
nr_dying_subsys_misc 0
Another sample output from system.slice/cgroup.stat was:
nr_descendants 34
nr_subsys_cpuset 0
nr_subsys_cpu 32
nr_subsys_io 32
nr_subsys_memory 34
nr_subsys_perf_event 35
nr_subsys_hugetlb 0
nr_subsys_pids 34
nr_subsys_rdma 0
nr_subsys_misc 0
nr_dying_descendants 30
nr_dying_subsys_cpuset 0
nr_dying_subsys_cpu 0
nr_dying_subsys_io 0
nr_dying_subsys_memory 30
nr_dying_subsys_perf_event 0
nr_dying_subsys_hugetlb 0
nr_dying_subsys_pids 0
nr_dying_subsys_rdma 0
nr_dying_subsys_misc 0
Note that 'debug' controller wasn't used to provide this information because
the controller is not recommended in productions kernels, also many of them
won't enable CONFIG_CGROUP_DEBUG by default.
Similar information could be retrieved with debuggers like drgn but that's
also not always available (e.g. lockdown) and the additional cost of runtime
tracking here is deemed marginal.
tj: Added Michal's paragraphs on why this is not added the debug controller
to the commit message.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Cc: Michal Koutný <mkoutny@suse.com>
Link: http://lkml.kernel.org/r/20240715150034.2583772-1-longman@redhat.com
Signed-off-by: Tejun Heo <tj@kernel.org>
