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Add GPL-2.0 SPDX license id lines to a few old
files, replacing the reference to the COPYING file.
The COPYING file at the time of creation of these files
(2007 and 2005) was GPL-v2.0, with an additional clause
indicating that only v2 applied.
Signed-off-by: Tim Bird <tim.bird@sony.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A warning was triggered as follows:
WARNING: kernel/cgroup/cpuset.c:1651 at remote_partition_disable+0xf7/0x110
RIP: 0010:remote_partition_disable+0xf7/0x110
RSP: 0018:ffffc90001947d88 EFLAGS: 00000206
RAX: 0000000000007fff RBX: ffff888103b6e000 RCX: 0000000000006f40
RDX: 0000000000006f00 RSI: ffffc90001947da8 RDI: ffff888103b6e000
RBP: ffff888103b6e000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: ffff88810b2e2728 R12: ffffc90001947da8
R13: 0000000000000000 R14: ffffc90001947da8 R15: ffff8881081f1c00
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f55c8bbe0b2 CR3: 000000010b14c000 CR4: 00000000000006f0
Call Trace:
<TASK>
update_prstate+0x2d3/0x580
cpuset_partition_write+0x94/0xf0
kernfs_fop_write_iter+0x147/0x200
vfs_write+0x35d/0x500
ksys_write+0x66/0xe0
do_syscall_64+0x6b/0x390
entry_SYSCALL_64_after_hwframe+0x4b/0x53
RIP: 0033:0x7f55c8cd4887
Reproduction steps (on a 16-CPU machine):
# cd /sys/fs/cgroup/
# mkdir A1
# echo +cpuset > A1/cgroup.subtree_control
# echo "0-14" > A1/cpuset.cpus.exclusive
# mkdir A1/A2
# echo "0-14" > A1/A2/cpuset.cpus.exclusive
# echo "root" > A1/A2/cpuset.cpus.partition
# echo 0 > /sys/devices/system/cpu/cpu15/online
# echo member > A1/A2/cpuset.cpus.partition
When CPU 15 is offlined, subpartitions_cpus gets cleared because no CPUs
remain available for the top_cpuset, forcing partitions to share CPUs with
the top_cpuset. In this scenario, disabling the remote partition triggers
a warning stating that effective_xcpus is not a subset of
subpartitions_cpus. Partitions should be invalidated in this case to
inform users that the partition is now invalid(cpus are shared with
top_cpuset).
To fix this issue:
1. Only emit the warning only if subpartitions_cpus is not empty and the
effective_xcpus is not a subset of subpartitions_cpus.
2. During the CPU hotplug process, invalidate partitions if
subpartitions_cpus is empty.
Fixes: f62a5d39368e ("cgroup/cpuset: Remove remote_partition_check() & make update_cpumasks_hier() handle remote partition")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup updates from Tejun Heo:
- Defer task cgroup unlink until after the dying task's final context
switch so that controllers see the cgroup properly populated until
the task is truly gone
- cpuset cleanups and simplifications.
Enforce that domain isolated CPUs stay in root or isolated partitions
and fail if isolated+nohz_full would leave no housekeeping CPU. Fix
sched/deadline root domain handling during CPU hot-unplug and race
for tasks in attaching cpusets
- Misc fixes including memory reclaim protection documentation and
selftest KTAP conformance
* tag 'cgroup-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
cpuset: Treat cpusets in attaching as populated
sched/deadline: Walk up cpuset hierarchy to decide root domain when hot-unplug
cgroup/cpuset: Introduce cpuset_cpus_allowed_locked()
docs: cgroup: No special handling of unpopulated memcgs
docs: cgroup: Note about sibling relative reclaim protection
docs: cgroup: Explain reclaim protection target
selftests/cgroup: conform test to KTAP format output
cpuset: remove need_rebuild_sched_domains
cpuset: remove global remote_children list
cpuset: simplify node setting on error
cgroup: include missing header for struct irq_work
cgroup: Fix sleeping from invalid context warning on PREEMPT_RT
cgroup/cpuset: Globally track isolated_cpus update
cgroup/cpuset: Ensure domain isolated CPUs stay in root or isolated partition
cgroup/cpuset: Move up prstate_housekeeping_conflict() helper
cgroup/cpuset: Fail if isolated and nohz_full don't leave any housekeeping
cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_isolation_cpumasks()
cgroup: Defer task cgroup unlink until after the task is done switching out
cgroup: Move dying_tasks cleanup from cgroup_task_release() to cgroup_task_free()
cgroup: Rename cgroup lifecycle hooks to cgroup_task_*()
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer core updates from Thomas Gleixner:
- Prevent a thundering herd problem when the timekeeper CPU is delayed
and a large number of CPUs compete to acquire jiffies_lock to do the
update. Limit it to one CPU with a separate "uncontended" atomic
variable.
- A set of improvements for the timer migration mechanism:
- Support imbalanced NUMA trees correctly
- Support dynamic exclusion of CPUs from the migrator duty to allow
the cpuset/isolation mechanism to exclude them from handling
timers of remote idle CPUs
- The usual small updates, cleanups and enhancements
* tag 'timers-core-2025-11-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timers/migration: Exclude isolated cpus from hierarchy
cpumask: Add initialiser to use cleanup helpers
sched/isolation: Force housekeeping if isolcpus and nohz_full don't leave any
cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_isolation_cpumasks()
timers/migration: Use scoped_guard on available flag set/clear
timers/migration: Add mask for CPUs available in the hierarchy
timers/migration: Rename 'online' bit to 'available'
selftests/timers/nanosleep: Add tests for return of remaining time
selftests/timers: Clean up kernel version check in posix_timers
time: Fix a few typos in time[r] related code comments
time: tick-oneshot: Add missing Return and parameter descriptions to kernel-doc
hrtimer: Store time as ktime_t in restart block
timers/migration: Remove dead code handling idle CPU checking for remote timers
timers/migration: Remove unused "cpu" parameter from tmigr_get_group()
timers/migration: Assert that hotplug preparing CPU is part of stable active hierarchy
timers/migration: Fix imbalanced NUMA trees
timers/migration: Remove locking on group connection
timers/migration: Convert "while" loops to use "for"
tick/sched: Limit non-timekeeper CPUs calling jiffies update
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Currently, the check for whether a partition is populated does not
account for tasks in the cpuset of attaching. This is a corner case
that can leave a task stuck in a partition with no effective CPUs.
The race condition occurs as follows:
cpu0 cpu1
//cpuset A with cpu N
migrate task p to A
cpuset_can_attach
// with effective cpus
// check ok
// cpuset_mutex is not held // clear cpuset.cpus.exclusive
// making effective cpus empty
update_exclusive_cpumask
// tasks_nocpu_error check ok
// empty effective cpus, partition valid
cpuset_attach
...
// task p stays in A, with non-effective cpus.
To fix this issue, this patch introduces cs_is_populated, which considers
tasks in the attaching cpuset. This new helper is used in validate_change
and partition_is_populated.
Fixes: e2d59900d936 ("cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The timer migration mechanism allows active CPUs to pull timers from
idle ones to improve the overall idle time. This is however undesired
when CPU intensive workloads run on isolated cores, as the algorithm
would move the timers from housekeeping to isolated cores, negatively
affecting the isolation.
Exclude isolated cores from the timer migration algorithm, extend the
concept of unavailable cores, currently used for offline ones, to
isolated ones:
* A core is unavailable if isolated or offline;
* A core is available if non isolated and online;
A core is considered unavailable as isolated if it belongs to:
* the isolcpus (domain) list
* an isolated cpuset
Except if it is:
* in the nohz_full list (already idle for the hierarchy)
* the nohz timekeeper core (must be available to handle global timers)
CPUs are added to the hierarchy during late boot, excluding isolated
ones, the hierarchy is also adapted when the cpuset isolation changes.
Due to how the timer migration algorithm works, any CPU part of the
hierarchy can have their global timers pulled by remote CPUs and have to
pull remote timers, only skipping pulling remote timers would break the
logic.
For this reason, prevent isolated CPUs from pulling remote global
timers, but also the other way around: any global timer started on an
isolated CPU will run there. This does not break the concept of
isolation (global timers don't come from outside the CPU) and, if
considered inappropriate, can usually be mitigated with other isolation
techniques (e.g. IRQ pinning).
This effect was noticed on a 128 cores machine running oslat on the
isolated cores (1-31,33-63,65-95,97-127). The tool monopolises CPUs,
and the CPU with lowest count in a timer migration hierarchy (here 1
and 65) appears as always active and continuously pulls global timers,
from the housekeeping CPUs. This ends up moving driver work (e.g.
delayed work) to isolated CPUs and causes latency spikes:
before the change:
# oslat -c 1-31,33-63,65-95,97-127 -D 62s
...
Maximum: 1203 10 3 4 ... 5 (us)
after the change:
# oslat -c 1-31,33-63,65-95,97-127 -D 62s
...
Maximum: 10 4 3 4 3 ... 5 (us)
The same behaviour was observed on a machine with as few as 20 cores /
40 threads with isocpus set to: 1-9,11-39 with rtla-osnoise-top.
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: John B. Wyatt IV <jwyatt@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://patch.msgid.link/20251120145653.296659-8-gmonaco@redhat.com
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update_isolation_cpumasks()
update_unbound_workqueue_cpumask() updates unbound workqueues settings
when there's a change in isolated CPUs, but it can be used for other
subsystems requiring updated when isolated CPUs change.
Generalise the name to update_isolation_cpumasks() to prepare for other
functions unrelated to workqueues to be called in that spot.
[longman: Change the function name to update_isolation_cpumasks()]
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://patch.msgid.link/20251120145653.296659-5-gmonaco@redhat.com
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cpuset_cpus_allowed() uses a reader lock that is sleepable under RT,
which means it cannot be called inside raw_spin_lock_t context.
Introduce a new cpuset_cpus_allowed_locked() helper that performs the
same function as cpuset_cpus_allowed() except that the caller must have
acquired the cpuset_mutex so that no further locking will be needed.
Suggested-by: Waiman Long <longman@redhat.com>
Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Waiman Long <longman@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: linux-kernel@vger.kernel.org
To: cgroups@vger.kernel.org
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Previously, update_cpumasks_hier() used need_rebuild_sched_domains to
decide whether to invoke rebuild_sched_domains_locked(). Now that
rebuild_sched_domains_locked() only sets force_rebuild, the flag is
redundant. Hence, remove it.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The remote_children list is used to track all remote partitions attached
to a cpuset. However, it serves no other purpose. Using a boolean flag to
indicate whether a cpuset is a remote partition is a more direct approach,
making remote_children unnecessary.
This patch replaces the list with a remote_partition flag in the cpuset
structure and removes remote_children entirely.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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There is no need to jump to the 'done' label upon failure, as no cleanup
is required. Return the error code directly instead.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The current cpuset code passes a local isolcpus_updated flag around in a
number of functions to determine if external isolation related cpumasks
like wq_unbound_cpumask should be updated. It is a bit cumbersome and
makes the code more complex. Simplify the code by using a global boolean
flag "isolated_cpus_updating" to track this. This flag will be set in
isolated_cpus_update() and cleared in update_isolation_cpumasks().
No functional change is expected.
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Commit 4a74e418881f ("cgroup/cpuset: Check partition conflict with
housekeeping setup") is supposed to ensure that domain isolated CPUs
designated by the "isolcpus" boot command line option stay either in
root partition or in isolated partitions. However, the required check
wasn't implemented when a remote partition was created or when an
existing partition changed type from "root" to "isolated".
Even though this is a relatively minor issue, we still need to add the
required prstate_housekeeping_conflict() call in the right places to
ensure that the rule is strictly followed.
The following steps can be used to reproduce the problem before this
fix.
# fmt -1 /proc/cmdline | grep isolcpus
isolcpus=9
# cd /sys/fs/cgroup/
# echo +cpuset > cgroup.subtree_control
# mkdir test
# echo 9 > test/cpuset.cpus
# echo isolated > test/cpuset.cpus.partition
# cat test/cpuset.cpus.partition
isolated
# cat test/cpuset.cpus.effective
9
# echo root > test/cpuset.cpus.partition
# cat test/cpuset.cpus.effective
9
# cat test/cpuset.cpus.partition
root
With this fix, the last few steps will become:
# echo root > test/cpuset.cpus.partition
# cat test/cpuset.cpus.effective
0-8,10-95
# cat test/cpuset.cpus.partition
root invalid (partition config conflicts with housekeeping setup)
Reported-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Move up the prstate_housekeeping_conflict() helper so that it can be
used in remote partition code.
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently the user can set up isolated cpus via cpuset and nohz_full in
such a way that leaves no housekeeping CPU (i.e. no CPU that is neither
domain isolated nor nohz full). This can be a problem for other
subsystems (e.g. the timer wheel imgration).
Prevent this configuration by blocking any assignation that would cause
the union of domain isolated cpus and nohz_full to covers all CPUs.
[longman: Remove isolated_cpus_should_update() and rewrite the checking
in update_prstate() and update_parent_effective_cpumask()]
Originally-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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update_isolation_cpumasks()
update_unbound_workqueue_cpumask() updates unbound workqueues settings
when there's a change in isolated CPUs, but it can be used for other
subsystems requiring updated when isolated CPUs change.
Generalise the name to update_isolation_cpumasks() to prepare for other
functions unrelated to workqueues to be called in that spot.
[longman: Change the function name to update_isolation_cpumasks()]
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The cpuset structure has a nr_subparts field which tracks the number
of child local partitions underneath a particular cpuset. Right now,
nr_subparts is only used in partition_is_populated() to avoid iteration
of child cpusets if the condition is right. So by always performing the
child iteration, we can avoid tracking the number of child partitions
and simplify the code a bit.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Hopefully saner naming.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
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The is_prs_invalid helper function is redundant as it serves a similar
purpose to is_partition_invalid. It can be fully replaced by the existing
is_partition_invalid function, so this patch removes the is_prs_invalid
helper.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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If the parent is not a valid partition, an error will be returned before
any partition update command is processed. This means the
WARN_ON_ONCE(!is_partition_valid(parent)) can never be triggered, so
it is safe to remove.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The nodelist_parse function already handles empty nodemask input
appropriately, making it unnecessary to handle this case separately
during the node mask update process.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The commit c6366739804f ("cpuset: refactor cpus_allowed_validate_change")
inadvertently removed the error return when cpus_allowed_validate_change()
fails. This patch restores the proper error handling by returning retval
when the validation check fails.
Fixes: c6366739804f ("cpuset: refactor cpus_allowed_validate_change")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A previous patch fixed a bug where new_prs should be assigned before
checking housekeeping conflicts. This patch addresses another potential
issue: the nocpu error check currently uses the xcpus which is not updated.
Although no issue has been observed so far, the check should be performed
using the new effective exclusive cpus.
The comment has been removed because the function returns an error if
nocpu checking fails, which is unrelated to the parent.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The 'isolcpus' parameter specified at boot time can be assigned to an
isolated partition. While it is valid put the 'isolcpus' in an isolated
partition, attempting to change a member cpuset to an isolated partition
will fail if the cpuset contains any 'isolcpus'.
For example, the system boots with 'isolcpus=9', and the following
configuration works correctly:
# cd /sys/fs/cgroup/
# mkdir test
# echo 1 > test/cpuset.cpus
# echo isolated > test/cpuset.cpus.partition
# cat test/cpuset.cpus.partition
isolated
# echo 9 > test/cpuset.cpus
# cat test/cpuset.cpus.partition
isolated
# cat test/cpuset.cpus
9
However, the following steps to convert a member cpuset to an isolated
partition will fail:
# cd /sys/fs/cgroup/
# mkdir test
# echo 9 > test/cpuset.cpus
# echo isolated > test/cpuset.cpus.partition
# cat test/cpuset.cpus.partition
isolated invalid (partition config conflicts with housekeeping setup)
The issue occurs because the new partition state (new_prs) is used for
validation against housekeeping constraints before it has been properly
updated. To resolve this, move the assignment of new_prs before the
housekeeping validation check when enabling a root partition.
Fixes: 4a74e418881f ("cgroup/cpuset: Check partition conflict with housekeeping setup")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A previous patch has introduced a new helper function
partition_cpus_change(). Now replace the exclusive cpus setting logic
with this helper function.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Previous patches made parse_cpulist handle empty cpu mask input.
Now use this helper for exclusive cpus setting. Also, compute_trialcs_xcpus
can be called with empty cpus and handles it correctly.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Introduce the partition_cpus_change function to handle both regular CPU
set updates and exclusive CPU modifications, either of which may trigger
partition state changes. This generalized function will also be utilized
for exclusive CPU updates in subsequent patches.
With the introduction of compute_trialcs_excpus in a previous patch,
the trialcs->effective_xcpus field is now consistently computed and
maintained. Consequently, the legacy logic which assigned
**trialcs->allowed_cpus to a local 'xcpus' variable** when
trialcs->effective_xcpus was empty has been removed.
This removal is safe because when trialcs is not a partition member,
trialcs->effective_xcpus is now correctly populated with the intersection
of user_xcpus and the parent's effective_xcpus. This calculation inherently
covers the scenario previously handled by the removed code.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Refactor cpus_allowed_validate_change to handle the special case where
cpuset.cpus can be set even when violating partition sibling CPU
exclusivity rules. This differs from the general validation logic in
validate_change. Add a wrapper function to properly handle this
exceptional case.
The trialcs->prs_err field is cleared before performing validation checks
for both CPU changes and partition errors. If cpus_allowed_validate_change
fails its validation, trialcs->prs_err is set to PERR_NOTEXCL. If partition
validation fails, the specific error code returned by validate_partition
is assigned to trialcs->prs_err.
With the partition validation status now directly available through
trialcs->prs_err, the local boolean variable 'invalidate' becomes
redundant and can be safely removed.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Refactor the validate_partition function to handle cpuset partition
validation when modifying cpuset.cpus. This refactoring also makes the
function reusable for handling cpuset.cpus.exclusive updates in subsequent
patches.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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This patch adds cpus_excl_conflict() and mems_excl_conflict() helper
functions to improve code readability and maintainability. The exclusive
conflict checking follows these rules:
1. If either cpuset has the 'exclusive' flag set, their user_xcpus must
not have any overlap.
2. If neither cpuset has the 'exclusive' flag set, their
'cpuset.cpus.exclusive' (only for v2) values must not intersect.
3. The 'cpuset.cpus' of one cpuset must not form a subset of another
cpuset's 'cpuset.cpus.exclusive'.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The current implementation contains redundant handling for empty mask
inputs, as cpulist_parse() already properly handles these cases. This
refactoring introduces a new helper function parse_cpuset_cpulist() to
consolidate CPU list parsing logic and eliminate special-case checks for
empty inputs.
Additionally, the effective_xcpus computation for trial cpusets has been
simplified. Rather than computing effective_xcpus only when exclusive_cpus
is set or when the cpuset forms a valid partition, we now recalculate it
on every cpuset.cpus update. This approach ensures consistency and allows
removal of redundant effective_xcpus logic in subsequent patches.
The trial cpuset's effective_xcpus calculation follows two distinct cases:
1. For member cpusets: effective_xcpus is determined by the intersection
of cpuset->exclusive_cpus and the parent's effective_xcpus.
2. For non-member cpusets: effective_xcpus is derived from the intersection
of user_xcpus and the parent's effective_xcpus.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The current compute_effective_exclusive_cpumask function handles multiple
scenarios with different input parameters, making the code difficult to
follow. This patch refactors it into two separate functions:
compute_excpus and compute_trialcs_excpus.
The compute_excpus function calculates the exclusive CPU mask for a given
input and excludes exclusive CPUs from sibling cpusets when cs's
exclusive_cpus is not explicitly set.
The compute_trialcs_excpus function specifically handles exclusive CPU
computation for trial cpusets used during CPU mask configuration updates,
and always excludes exclusive CPUs from sibling cpusets.
This refactoring significantly improves code readability and clarity,
making it explicit which function to call for each use case and what
parameters should be provided.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The functions is_partition_valid() and is_partition_invalid() logically
return boolean values, but were previously declared with return type
'int'. This patch changes their return type to 'bool' to better reflect
their semantic meaning and improve type safety.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The trialcs->partition_root_state field is not used during the
configuration of 'cpuset.cpus' or 'cpuset.cpus.exclusive'. Therefore,
the assignment of values to this field can be safely removed.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The 'cpus' or 'mems' lists of the top_cpuset cannot be modified.
This check can be moved before acquiring any locks as a common code
block to improve efficiency and maintainability.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Since commit a8bb74acd8efe ("rcu: Consolidate RCU-sched update-side function definitions")
there is no difference between rcu_read_lock(), rcu_read_lock_bh() and
rcu_read_lock_sched() in terms of RCU read section and the relevant grace
period. That means that spin_lock(), which implies rcu_read_lock_sched(),
also implies rcu_read_lock().
There is no need no explicitly start a RCU read section if one has already
been started implicitly by spin_lock().
Simplify the code and remove the inner rcu_read_lock() invocation.
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: pengdonglin <pengdonglin@xiaomi.com>
Signed-off-by: pengdonglin <dolinux.peng@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Now in cpuset_attach(), we need to synchronously wait for
flush_workqueue to complete. The execution time of flushing
cpuset_migrate_mm_wq depends on the amount of mm migration initiated by
cpusets at that time. When the cpuset.mems of a cgroup occupying a large
amount of memory is modified, it may trigger extensive mm migration,
causing cpuset_attach() to block on flush_workqueue for an extended period.
This could be dangerous because cpuset_attach() is within the critical
section of cgroup_mutex, which may ultimately cause all cgroup-related
operations in the system to be blocked.
This patch attempts to defer the flush_workqueue() operation until
returning to userspace using the task_work which is originally proposed by
tejun[1], so that flush happens after cgroup_mutex is dropped. That way we
maintain the operation synchronicity while avoiding bothering anyone else.
[1]: https://lore.kernel.org/cgroups/ZgMFPMjZRZCsq9Q-@slm.duckdns.org/T/#m117f606fa24f66f0823a60f211b36f24bd9e1883
Originally-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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It is unnecessary to always wait for the flush operation of
cpuset_migrate_mm_wq to complete in cpuset_write_resmask, as modifying
cpuset.cpus or cpuset.exclusive does not trigger mm migrations. The
flush_workqueue can be executed only when cpuset.mems is modified.
Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Commit 5806b3d05165 ("cpuset: decouple tmpmasks and cpumasks freeing in
cgroup") separates out the freeing of tmpmasks into a new free_tmpmask()
helper but removes the NULL pointer check in the process. Unfortunately a
NULL pointer can be passed to free_tmpmasks() in cpuset_handle_hotplug()
if cpuset v1 is active. This can cause segmentation fault and crash
the kernel.
Fix that by adding the NULL pointer check to free_tmpmasks().
Fixes: 5806b3d05165 ("cpuset: decouple tmpmasks and cpumasks freeing in cgroup")
Reported-by: Ashay Jaiswal <quic_ashayj@quicinc.com>
Closes: https://lore.kernel.org/lkml/20250902-cpuset-free-on-condition-v1-1-f46ffab53eac@quicinc.com/
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset: add helpers for cpus_read_lock and cpuset_mutex locks.
Replace repetitive locking patterns with new helpers:
- cpuset_full_lock()
- cpuset_full_unlock()
This makes the code cleaner and ensures consistent lock ordering.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The original alloc_cpumasks() served dual purposes: allocating cpumasks
for both temporary masks (tmpmasks) and cpuset structures. This patch:
1. Decouples these allocation paths for better code clarity
2. Introduces dedicated alloc_tmpmasks() and dup_or_alloc_cpuset()
functions
3. Maintains symmetric pairing:
- alloc_tmpmasks() ↔ free_tmpmasks()
- dup_or_alloc_cpuset() ↔ free_cpuset()
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Currently, free_cpumasks() can free both tmpmasks and cpumasks of a cpuset
(cs). However, these two operations are not logically coupled. To improve
code clarity:
1. Move cpumask freeing to free_cpuset()
2. Rename free_cpumasks() to free_tmpmasks()
This change enforces the single responsibility principle.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The CS_ONLINE flag was introduced prior to the CSS_ONLINE flag in the
cpuset subsystem. Currently, the flag setting sequence is as follows:
1. cpuset_css_online() sets CS_ONLINE
2. css->flags gets CSS_ONLINE set
...
3. cgroup->kill_css sets CSS_DYING
4. cpuset_css_offline() clears CS_ONLINE
5. css->flags clears CSS_ONLINE
The is_cpuset_online() check currently occurs between steps 1 and 3.
However, it would be equally safe to perform this check between steps 2
and 3, as CSS_ONLINE provides the same synchronization guarantee as
CS_ONLINE.
Since CS_ONLINE is redundant with CSS_ONLINE and provides no additional
synchronization benefits, we can safely remove it to simplify the code.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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The css_get/put() calls in cpuset_partition_write() are unnecessary as
an active reference of the kernfs node will be taken which will prevent
its removal and guarantee the existence of the css. Only the online
check is needed.
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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It was found during testing that an invalid leaf partition with an
empty effective exclusive CPU list can become a valid empty partition
with no CPU afer an offline/online operation of an unrelated CPU. An
empty partition root is allowed in the special case that it has no
task in its cgroup and has distributed out all its CPUs to its child
partitions. That is certainly not the case here.
The problem is in the cpumask_subsets() test in the hotplug case
(update with no new mask) of update_parent_effective_cpumask() as it
also returns true if the effective exclusive CPU list is empty. Fix that
by addding the cpumask_empty() test to root out this exception case.
Also add the cpumask_empty() test in cpuset_hotplug_update_tasks()
to avoid calling update_parent_effective_cpumask() for this special case.
Fixes: 0c7f293efc87 ("cgroup/cpuset: Add cpuset.cpus.exclusive.effective for v2")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpusets_insane_config_key
The following lockdep splat was observed.
[ 812.359086] ============================================
[ 812.359089] WARNING: possible recursive locking detected
[ 812.359097] --------------------------------------------
[ 812.359100] runtest.sh/30042 is trying to acquire lock:
[ 812.359105] ffffffffa7f27420 (cpu_hotplug_lock){++++}-{0:0}, at: static_key_enable+0xe/0x20
[ 812.359131]
[ 812.359131] but task is already holding lock:
[ 812.359134] ffffffffa7f27420 (cpu_hotplug_lock){++++}-{0:0}, at: cpuset_write_resmask+0x98/0xa70
:
[ 812.359267] Call Trace:
[ 812.359272] <TASK>
[ 812.359367] cpus_read_lock+0x3c/0xe0
[ 812.359382] static_key_enable+0xe/0x20
[ 812.359389] check_insane_mems_config.part.0+0x11/0x30
[ 812.359398] cpuset_write_resmask+0x9f2/0xa70
[ 812.359411] cgroup_file_write+0x1c7/0x660
[ 812.359467] kernfs_fop_write_iter+0x358/0x530
[ 812.359479] vfs_write+0xabe/0x1250
[ 812.359529] ksys_write+0xf9/0x1d0
[ 812.359558] do_syscall_64+0x5f/0xe0
Since commit d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem
and hotplug lock order"), the ordering of cpu hotplug lock
and cpuset_mutex had been reversed. That patch correctly
used the cpuslocked version of the static branch API to enable
cpusets_pre_enable_key and cpusets_enabled_key, but it didn't do the
same for cpusets_insane_config_key.
The cpusets_insane_config_key can be enabled in the
check_insane_mems_config() which is called from update_nodemask()
or cpuset_hotplug_update_tasks() with both cpu hotplug lock and
cpuset_mutex held. Deadlock can happen with a pending hotplug event that
tries to acquire the cpu hotplug write lock which will block further
cpus_read_lock() attempt from check_insane_mems_config(). Fix that by
switching to use static_branch_enable_cpuslocked().
Fixes: d74b27d63a8b ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock order")
Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset is only concerned when a numa node changes its memory state, as it
needs to know the current numa nodes with memory to keep an updated
mems_allowed mask. So stop using the memory notifier and use the new numa
node notifer instead.
Link: https://lkml.kernel.org/r/20250616135158.450136-9-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull MM updates from Andrew Morton:
- "Add folio_mk_pte()" from Matthew Wilcox simplifies the act of
creating a pte which addresses the first page in a folio and reduces
the amount of plumbing which architecture must implement to provide
this.
- "Misc folio patches for 6.16" from Matthew Wilcox is a shower of
largely unrelated folio infrastructure changes which clean things up
and better prepare us for future work.
- "memory,x86,acpi: hotplug memory alignment advisement" from Gregory
Price adds early-init code to prevent x86 from leaving physical
memory unused when physical address regions are not aligned to memory
block size.
- "mm/compaction: allow more aggressive proactive compaction" from
Michal |
