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a5b98009f16d ("sched/psi: fix race between file release and pressure write")
made pressure_write() hold cgroup_mutex across psi_trigger_create(), which
forks the psimon kthread for the first rtpoll trigger. As kthread creation
depends on the whole fork path, the commit inadvertently created a lot of
unwanted locking dependencies from cgroup_mutex.
sched_ext got hit by one: its enable path blocks forks and then grabs
cgroup_mutex, so a pressure write racing a scheduler enable deadlocks, with
every other fork piling up behind.
Fix it by splitting trigger creation so that the worker is forked with
cgroup_mutex dropped and the kernfs active reference left broken. The latter
matters because rmdir and cgroup.pressure writes drain active references
under cgroup_mutex. Publishing the trigger last keeps error reporting
synchronous and preserves the of->priv lifetime rules.
The trigger registered in the first stage pins the group's rtpoll machinery
across the unlocked window, leaving only creation races to resolve. The
catch-up poll on installation covers scheduling attempts dropped while there
was no worker.
v2: Retagged sched/psi (was cgroup).
Fixes: a5b98009f16d ("sched/psi: fix race between file release and pressure write")
Cc: stable@vger.kernel.org
Cc: Edward Adam Davis <eadavis@qq.com>
Cc: Chen Ridong <chenridong@huaweicloud.com>
Reported-by: Matt Fleming <mfleming@cloudflare.com>
Closes: https://lore.kernel.org/all/20260710100441.2653477-1-matt@readmodwrite.com/
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Tested-by: Matt Fleming <mfleming@cloudflare.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
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Creating a child cpuset where cpuset.mems is never set leads to a div/0
when a VMA mempolicy with MPOL_F_RELATIVE_NODES rebinds in response to a
CPU hotplug event.
Reproduction steps:
1) Create a cgroup w/ cpuset controls (do not set cpuset.mems)
2) Move the task into the child cpuset
3) Create a VMA mempolicy for that task with MPOL_F_RELATIVE_NODES
4) unplug and hotplug a cpu
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
5) mempolicy rebind does a div/0 in mpol_relative_nodemask on the
call to __nodes_fold()
The cpuset code passes (cs->mems_allowed) which is not guaranteed to have
nodes to the rebind routine. Use cs->effective_mems instead, which is
guaranteed to have a non-empty nodemask once we reach that code path.
Link: https://lore.kernel.org/all/CA+0ovCiEz6SP_sn3kN4Tb+_oC=eHMXy_Ffj=usV3wREdQrUtww@mail.gmail.com/
Fixes: ae1c802382f7 ("cpuset: apply cs->effective_{cpus,mems}")
Closes: https://lore.kernel.org/linux-mm/CA+0ovCgxbZkXa+OU8w3s84R3KNPNxxRfmsNR-udh+afQBbGNmw@mail.gmail.com/
Suggested-by: Gregory Price <gourry@gourry.net>
Suggested-by: Waiman Long <longman@redhat.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Farhad Alemi <farhad.alemi@berkeley.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Gregory Price <gourry@gourry.net>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ridong Chen <ridong.chen@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Michal Koutný" <mkoutny@suse.com>
Cc: <stable@vger.kernel.org>
[ david: add a comment, slightly rephrase description ]
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
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:
- Last cycle deferred css teardown on cgroup removal until the cgroup
depopulated, so a css is not taken offline while tasks can still
reference it. Disabling a controller through cgroup.subtree_control
still had the same problem. This reworks the deferral from per-cgroup
to per-css so that path is covered too.
- New RDMA controller monitoring files: rdma.peak for per-device peak
usage and rdma.events / rdma.events.local for resource-limit
exhaustion. The max-limit parser was rewritten, fixing two input
parsing bugs.
- cpuset: fix a sched-domain leak on the domain-rebuild failure path
and skip a redundant hardwall ancestor scan on v2.
- Misc: pair the remaining lockless cgroup.max.* reads with WRITE_ONCE,
assorted selftest robustness fixes, and doc path corrections.
* tag 'cgroup-for-7.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (22 commits)
cgroup: Migrate tasks to the root css when a controller is rebound
docs: cgroup: Fix stale source file paths
cgroup/cpuset: Free sched domains on rebuild guard failure
cgroup: pair max limit READ_ONCE() with WRITE_ONCE()
selftests/cgroup: enable memory controller in hugetlb memcg test
cgroup/rdma: Drop unnecessary READ_ONCE() on event counters
cgroup: Defer kill_css_finish() in cgroup_apply_control_disable()
cgroup: Add per-subsys-css kill_css_finish deferral
cgroup: Move populated counters to cgroup_subsys_state
cgroup: Annotate unlocked nr_populated_* accesses with READ_ONCE/WRITE_ONCE
cgroup: Inline cgroup_has_tasks() in cgroup.h
cgroup/rdma: document rdma.peak, rdma.events and rdma.events.local
cgroup/rdma: add rdma.events.local for per-cgroup allocation failure attribution
cgroup/rdma: add rdma.events to track resource limit exhaustion
cgroup/rdma: add rdma.peak for per-device peak usage tracking
selftests/cgroup: check malloc return value in alloc_anon functions
cgroup/cpuset: Skip hardwall ancestor scan in cpuset v2 in cpuset_current_node_allowed()
selftests/cgroup: fix misleading debug message in test_cgfreezer_time_child
selftests/cgroup: fix child process escaping to parent cleanup in test_cpucg_nice
selftests/cgroup: Add NULL check after malloc in cgroup_util.c
...
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo:
"One cpuset fix and a maintenance update, both low-risk:
- Fix cpuset partition CPU accounting under sibling CPU exclusion
that could produce wrong CPU assignments and trigger
scheduling-domain warnings. Includes selftests.
- Update an email address in MAINTAINERS"
* tag 'cgroup-for-7.1-rc6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Change Ridong's email
cgroup/cpuset: Add test cases for sibling CPU exclusion on partition update
cgroup/cpuset: Use effective_xcpus in partcmd_update add/del mask calculation
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cgroup_apply_control_disable() defers kill_css_finish() while a css is
still populated, relying on css_update_populated() to fire the deferred
kill once the populated count reaches zero.
This deadlocks when a controller is rebound out of a hierarchy. Mounting
an implicit_on_dfl controller such as perf_event as a v1 hierarchy steals
it off the default hierarchy, and rebind_subsystems() kills its
per-cgroup csses while they are still populated. The migration run in the
same step keeps the old css for a controller no longer in the hierarchy's
mask, so no task is migrated off the dying csses. Their populated count
never reaches zero, the deferred kill_css_finish() never fires, and the
next cgroup_lock_and_drain_offline() hangs forever under cgroup_mutex.
That migration is already a no-op pass over the rebound subtree. Add
cgroup_rebind_ss_mask so find_existing_css_set() resolves the leaving
controllers to the root css. Their tasks are migrated there, the
per-cgroup csses depopulate, and cgroup_apply_control_disable() kills
them synchronously. The deferral stays correct for the rmdir and
controller-disable paths it was meant for.
Fixes: 1dffd95575eb ("cgroup: Defer kill_css_finish() in cgroup_apply_control_disable()")
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/41cd159c-54e5-45e0-81df-eaf36a6c028e@sirena.org.uk/
Reported-by: Bert Karwatzki <spasswolf@web.de>
Closes: https://lore.kernel.org/all/4e986b4ed7e16547805d54b6e67d09120bc4d2f2.camel@web.de/
Tested-by: Mark Brown <broonie@kernel.org>
Tested-by: Bert Karwatzki <spasswolf@web.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
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generate_sched_domains() returns sched-domain masks and optional
attributes that are normally handed to partition_sched_domains(), which
takes ownership of them.
rebuild_sched_domains_locked() has a WARN guard after
generate_sched_domains() and before partition_sched_domains() to avoid
passing offline CPUs into the scheduler domain rebuild path. If that
guard fires, the function currently returns directly without freeing
the generated doms and attr.
Free the generated sched-domain masks and attributes before returning
from the guard failure path.
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cgroup.max.descendants and cgroup.max.depth are shown through seq_file.
Their show callbacks read cgrp->max_descendants and cgrp->max_depth with
READ_ONCE(), respectively.
The corresponding write callbacks update the same scalar fields while
holding the cgroup lock, but the seq_file show path does not serialize
against those stores. This leaves the lockless show-side loads annotated
with READ_ONCE(), while the corresponding stores remain plain stores.
Use WRITE_ONCE() for the updates so the intended lockless access is marked
consistently on both sides. This does not change locking, ordering, or
user-visible semantics.
Assisted-by: OpenAI-Codex:gpt-5.5
Signed-off-by: Ren Tamura <ren.tamura.oss@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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When sibling CPU exclusion occurs, a partition's user_xcpus may contain
CPUs that were never actually granted to it. These CPUs are present in
user_xcpus(cs) but not in cs->effective_xcpus.
The partcmd_update path in update_parent_effective_cpumask() uses
user_xcpus(cs) (via the local variable xcpus) to compute the addmask
(CPUs to return to parent) and delmask (CPUs to request from parent).
This is incorrect:
1) When newmask removes a CPU that was previously excluded by a
sibling, addmask incorrectly includes that CPU and tries to return
it to the parent even though the partition never actually owned it,
causing CPU overlap with sibling partitions and triggering warnings
in generate_sched_domains().
2) When newmask adds a previously excluded CPU that is now available,
delmask fails to request it from the parent because user_xcpus(cs)
already includes it.
Fix this by using cs->effective_xcpus instead of user_xcpus(cs) in all
partcmd_update paths that calculate addmask or delmask, including the
PERR_NOCPUS error handling paths.
Reproducers:
Example 1 - Removing a sibling-excluded CPU incorrectly returns it:
# cd /sys/fs/cgroup
# echo "0-1" > a1/cpuset.cpus
# echo "root" > a1/cpuset.cpus.partition
# echo "0-2" > b1/cpuset.cpus
# echo "root" > b1/cpuset.cpus.partition
# echo "2" > b1/cpuset.cpus
# cat cpuset.cpus.effective
# Actual: 0-1,3 Expected: 3
Example 2 - Expanding to a previously excluded CPU fails to request it:
# cd /sys/fs/cgroup
# echo "0-1" > a1/cpuset.cpus
# echo "root" > a1/cpuset.cpus.partition
# echo "0-2" > b1/cpuset.cpus
# echo "root" > b1/cpuset.cpus.partition
# echo "member" > a1/cpuset.cpus.partition
# echo "1-2" > b1/cpuset.cpus
# cat cpuset.cpus.effective
# Actual: 0-1,3 Expected: 0,3
Fixes: 2a3602030d80 ("cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict")
Cc: stable@vger.kernel.org # v7.0+
Suggested-by: Zhang Guopeng <zhangguopeng@kylinos.cn>
Signed-off-by: Sun Shaojie <sunshaojie@kylinos.cn>
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 fixes from Tejun Heo:
"Two rstat fixes:
- Out-of-bounds access in the css_rstat_updated() BPF kfunc when
called with an unchecked user-supplied cpu
- Over-strict NMI guard after the recent switch to try_cmpxchg left
sparc and ppc64 unable to queue rstat updates from NMI"
* tag 'cgroup-for-7.1-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: rstat: relax NMI guard after switch to try_cmpxchg
cgroup/rstat: validate cpu before css_rstat_cpu() access
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Commit 36df6e3dbd7e ("cgroup: make css_rstat_updated nmi safe") used
this_cpu_cmpxchg() for the lockless insertion, and therefore required
both ARCH_HAVE_NMI_SAFE_CMPXCHG and ARCH_HAS_NMI_SAFE_THIS_CPU_OPS in
the NMI guard: on archs without the latter, this_cpu_cmpxchg() falls
back to "local_irq_save() + plain cmpxchg", and local_irq_save()
cannot mask NMIs.
Commit 3309b63a2281 ("cgroup: rstat: use LOCK CMPXCHG in
css_rstat_updated") later replaced this_cpu_cmpxchg() with plain
try_cmpxchg() to fix cross-CPU lockless-list corruption, but left the
NMI guard untouched. After that switch, css_rstat_updated() no longer
performs any this_cpu_*() RMW operations and only relies on the arch
having NMI-safe cmpxchg, so ARCH_HAS_NMI_SAFE_THIS_CPU_OPS is no
longer required in the guard.
Relax the guard accordingly so that archs which have HAVE_NMI and
ARCH_HAVE_NMI_SAFE_CMPXCHG but not ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
(e.g. sparc, powerpc on PPC64/BOOK3S) can benefit from the existing
CONFIG_MEMCG_NMI_SAFETY_REQUIRES_ATOMIC path. Without this, the css
is never queued in NMI on those archs, and the atomics staged by
account_{slab,kmem}_nmi_safe() are not drained by flush_nmi_stats().
Fixes: 3309b63a2281 ("cgroup: rstat: use LOCK CMPXCHG in css_rstat_updated")
Signed-off-by: Cunlong Li <shenxiaogll@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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css_rstat_updated() is exposed as a BPF kfunc and accepts a
caller-provided cpu argument. The function uses cpu for per-cpu rstat
lookups without checking whether it refers to a valid possible CPU.
A BPF iter/cgroup program with CAP_BPF and CAP_PERFMON can pass an
invalid cpu value. On an unfixed UBSCAN_BOUNDS test kernel, cpu ==
0x7fffffff triggers:
UBSAN: array-index-out-of-bounds in kernel/cgroup/rstat.c:31:9
index 2147483647 is out of range for type 'long unsigned int [64]'
Call Trace:
css_rstat_updated
bpf_iter_run_prog
cgroup_iter_seq_show
bpf_seq_read
Add cpu validation to the BPF-facing css_rstat_updated() kfunc and
move the common implementation to __css_rstat_updated() for in-kernel
callers.
Fixes: a319185be9f5 ("cgroup: bpf: enable bpf programs to integrate with rstat")
Signed-off-by: Qing Ming <a0yami@mailbox.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
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All accesses to the event counters are serialized by rdmacg_mutex,
making the READ_ONCE() annotations unnecessary. Remove them.
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Same race shape as the rmdir path that 93618edf7538 ("cgroup: Defer css
percpu_ref kill on rmdir until cgroup is depopulated") fixed: a task past
exit_signals() whose cset subsys[ssid] still pins the disabled controller's
css can be touching subsys state while ->css_offline() runs. The earlier
patches in this series built up the per-subsys-css deferral machinery and
routed cgroup_destroy_locked() through it. Apply the same shape to
cgroup_apply_control_disable():
kill_css_sync(css);
if (!css_is_populated(css))
kill_css_finish(css);
When the dying css is still populated, kill_css_finish() is deferred. The
walker in css_update_populated() fires kill_finish_work once the css's
hierarchical populated count drops to zero.
cgroup_lock_and_drain_offline()'s wait predicate switches from
percpu_ref_is_dying() to css_is_dying(). CSS_DYING is set by kill_css_sync()
and is a strict superset of percpu_ref_is_dying. Without this change, a +cpu
re-enable after a deferred -cpu disable would skip the drain (percpu_ref
isn't killed yet) and observe the still-CSS_DYING css through cgroup_css(),
treating it as live.
Signed-off-by: Tejun Heo <tj@kernel.org>
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93618edf7538 ("cgroup: Defer css percpu_ref kill on rmdir until cgroup is
depopulated") deferred kill_css_finish() at the cgroup level: rmdir waits
for the entire cgroup's populated count to drop to zero, then fires
kill_css_finish() on every subsystem css at once. Replace that with
per-subsys-css deferral. Each subsystem css now tracks its own hierarchical
populated count and independently defers its kill_css_finish() until its own
subtree drains.
The rmdir-race fix carries through unchanged in shape. The dying css's
->css_offline() still waits until no PF_EXITING task references it, and v2's
cgroup-level machinery goes away.
cgroup_apply_control_disable() has the same race shape (PF_EXITING tasks
pinning a css whose ->css_offline() is about to run) and stays synchronous
here. This patch lays the groundwork for fixing it - per-cgroup waiting
can't gate one subsys css being killed while the rest of the cgroup stays
live, but per-css can.
Subtree-wide invariant preserved: a dying ancestor css stays populated
through nr_populated_children until every dying descendant's task drains, so
the walker fires the ancestor's kill_finish_work only after all descendants
have drained.
Add paired smp_mb()s in kill_css_sync() and css_update_populated() to fence
the StoreLoad on (CSS_DYING, populated counter), guaranteeing that either
the walker queues kill_finish_work or the caller fires synchronously.
cgroup_destroy_locked() was implicitly fenced by an unrelated css_set_lock
pair; cgroup_apply_control_disable() in the next patch is not.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Later patches replace the cgroup-level finish_destroy_work deferral added
by 93618edf7538 ("cgroup: Defer css percpu_ref kill on rmdir until cgroup
is depopulated") with a per-subsys-css deferral. That needs each subsystem
css to track its own populated count. Move the populated counters from
cgroup onto cgroup_subsys_state. cgroup->self is itself a
cgroup_subsys_state and self.parent walks the same chain as cgroup_parent(),
so cgroup_update_populated() generalizes to a single css_update_populated()
taking a css. The cgroup-side bookkeeping runs only when the walk started
from a self css.
Keep nr_populated_{domain,threaded}_children on cgroup. Both sum to
self.nr_populated_children, but staying as dedicated fields to allow readers
like cgroup_can_be_thread_root() unlocked access.
css_set_update_populated() also walks the per-subsys-css chain so each
subsystem css's hierarchical populated count is maintained. No reader
consumes those counts yet.
Signed-off-by: Tejun Heo <tj@kernel.org>
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cgroup_update_populated() updates nr_populated_csets,
nr_populated_domain_children, and nr_populated_threaded_children under
css_set_lock, but cgroup_has_tasks(), cgroup_is_populated(), and
cgroup_can_be_thread_root() read them without holding it. Use
READ_ONCE/WRITE_ONCE.
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset reads cs->css.cgroup->nr_populated_csets directly in two places to
test whether a cgroup has tasks. cgroup.c already has a matching helper,
cgroup_has_tasks(). Move it to cgroup.h as static inline and use that
instead. This is to prepare for relocation of cgroup->nr_populated_csets. No
semantic change.
Signed-off-by: Tejun Heo <tj@kernel.org>
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Add per-cgroup local event counters to track RDMA resource limit
exhaustion from the perspective of individual cgroups. The
rdma.events.local file reports two per-resource counters:
- max: number of times this cgroup's limit was the one that blocked
an allocation in the subtree
- alloc_fail: number of allocation attempts originating from this
cgroup that failed due to an ancestor's limit
This mirrors the design of pids.events.local, where events are
attributed to the cgroup that imposed the limit, not necessarily the
cgroup where the allocation was attempted.
Also extend rdma.events with a hierarchical alloc_fail counter that
tracks allocation failures propagating upward from the requesting
cgroup, complementing the existing max counter, so that rdma.events
and rdma.events.local share the same output format.
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Add per-device hierarchical event counters to track when RDMA resource
limits are exceeded. The rdma.events file reports max event counts
propagated upward from the cgroup whose limit was hit to all ancestors.
This mirrors the design of pids.events, where events are attributed to
the cgroup that imposed the limit, not necessarily the cgroup where the
allocation was attempted. Userspace can monitor this file via
poll/epoll for real-time notification of resource exhaustion.
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
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rdma.peak tracks the high watermark of resource usage per device,
giving a better baseline on which to set rdma.max. Polling
rdma.current isn't feasible since it would miss short-lived spikes.
This interface is analogous to memory.peak.
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
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 fixes from Tejun Heo:
- cpuset fixes:
- Partition invalidation could return CPUs still in use by sibling
partitions, producing overlapping effective_cpus
- cpuset_can_attach() over-reserved DL bandwidth on moves that
stayed within the same root domain
- Pending DL migration state leaked into later attaches when a
later can_attach() check failed
- Reorder PF_EXITING and __GFP_HARDWALL checks so dying tasks can
allocate from any node and exit quickly
- dmem: propagate -ENOMEM instead of spinning forever when the fallback
pool allocation also fails
- selftests/cgroup: percpu test error-path leak, bogus numeric
comparison of cpuset strings, and a zero-length read() that silently
passed OOM-kill tests
* tag 'cgroup-for-7.1-rc3-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Return only actually allocated CPUs during partition invalidation
selftests/cgroup: Fix error path leaks in test_percpu_basic
cgroup/cpuset: Reserve DL bandwidth only for root-domain moves
cgroup/cpuset: Reset DL migration state on can_attach() failure
selftests/cgroup: Fix string comparison in write_test
selftests/cgroup: Fix cg_read_strcmp() empty string comparison
cgroup/dmem: Return -ENOMEM on failed pool preallocation
cgroup/cpuset: move PF_EXITING check before __GFP_HARDWALL in cpuset_current_node_allowed()
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In update_parent_effective_cpumask() with partcmd_invalidate, the CPUs
to return to the parent are computed as:
adding = cpumask_and(tmp->addmask, xcpus, parent->effective_xcpus);
where xcpus = user_xcpus(cs) which returns cs->exclusive_cpus (if set)
or cs->cpus_allowed. When exclusive_cpus is not set, user_xcpus(cs) can
contain CPUs that were never actually granted to the partition due to
sibling exclusion in compute_excpus(). Consequently, the invalidation
may return CPUs to the parent that remain in use by sibling partitions,
causing overlapping effective_cpus and triggering the
WARN_ON_ONCE(1) in generate_sched_domains().
Use cs->effective_xcpus instead, which reflects the CPUs actually
granted to this partition.
Reproducer (on a 4-CPU machine):
cd /sys/fs/cgroup
mkdir a1 b1
# a1 becomes partition root with CPUs 0-1
echo "0-1" > a1/cpuset.cpus
echo "root" > a1/cpuset.cpus.partition
# b1 becomes partition root with CPUs 1-2, but sibling exclusion
# reduces its effective_xcpus to CPU 2 only
echo "1-2" > b1/cpuset.cpus
echo "root" > b1/cpuset.cpus.partition
# b1 changes cpus_allowed to 0-1 -> partition invalidation
echo "0-1" > b1/cpuset.cpus
# Expected: CPUs 2-3 (only CPU 2 returned from b1)
# Actual: CPUs 1-3 (CPU 0-1 returned, overlapping with a1)
cat cpuset.cpus.effective
dmesg will also show a WARNING from generate_sched_domains() reporting
overlapping partition root effective_cpus.
Fixes: 2a3602030d80 ("cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict")
Cc: stable@vger.kernel.org # v7.0+
Signed-off-by: sunshaojie <sunshaojie@kylinos.cn>
Tested-by: Chen Ridong <chenridong@huaweicloud.com>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset_can_attach() currently adds the bandwidth of all migrating
SCHED_DEADLINE tasks to sum_migrate_dl_bw. If the source and destination
cpuset effective CPU masks do not overlap, the whole sum is then
reserved in the destination root domain.
set_cpus_allowed_dl(), however, subtracts bandwidth from the source
root domain only when the affinity change really moves the task between
root domains. A DL task can move between cpusets that are still in the
same root domain, so including that task in sum_migrate_dl_bw can reserve
destination bandwidth without a matching source-side subtraction.
Share the root-domain move test with set_cpus_allowed_dl(). Keep
nr_migrate_dl_tasks counting all migrating deadline tasks for cpuset DL
task accounting, but add to sum_migrate_dl_bw only for tasks that need a
root-domain bandwidth move. Keep using the destination cpuset effective
CPU mask and leave the broader can_attach()/attach() transaction model
unchanged.
Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Cc: stable@vger.kernel.org # v6.10+
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Reviewed-by: Waiman Long <longman@redhat.com>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset_current_node_allowed()
Cgroup v2 doesn't have the concept of memory hardwall, only top_cpuset
has CS_MEM_EXCLUSIVE/CS_MEM_HARDWALL flags, nearest_hardwall_ancestor
always returns top_cpuset with all nodes set, so no need to acquire
callback_lock and scan up cpuset.
Suggested-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Chen Wandun <chenwandun@lixiang.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Pull to receive dde2f938d02f ("cgroup/cpuset: move PF_EXITING check
before __GFP_HARDWALL in cpuset_current_node_allowed()") as a
dependency for an upcoming patch in the same function.
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset_can_attach() accumulates temporary SCHED_DEADLINE migration
state in the destination cpuset while walking the taskset.
If a later task_can_attach() or security_task_setscheduler() check
fails, cgroup_migrate_execute() treats cpuset as the failing subsystem
and does not call cpuset_cancel_attach() for it. The partially
accumulated state is then left behind and can be consumed by a later
attach, corrupting cpuset DL task accounting and pending DL bandwidth
accounting.
Reset the pending DL migration state from the common error exit when
ret is non-zero. Successful can_attach() keeps the state for
cpuset_attach() or cpuset_cancel_attach().
Fixes: 2ef269ef1ac0 ("cgroup/cpuset: Free DL BW in case can_attach() fails")
Cc: stable@vger.kernel.org # v6.10+
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Chen Ridong <chenridong@huaweicloud.com>
Reviewed-by: Waiman Long <longman@redhat.com>
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get_cg_pool_unlocked() handles allocation failures under dmemcg_lock by
dropping the lock, preallocating a pool with GFP_KERNEL, and retrying the
locked lookup and creation path.
If the fallback allocation fails too, pool remains NULL. Since the loop
condition is while (!pool), the function can keep retrying instead of
propagating the allocation failure to the caller.
Set pool to ERR_PTR(-ENOMEM) when the fallback allocation fails so the
loop exits through the existing common return path. The callers already
handle ERR_PTR() from get_cg_pool_unlocked(), so this restores the
expected error path.
Fixes: b168ed458dde ("kernel/cgroup: Add "dmem" memory accounting cgroup")
Cc: stable@vger.kernel.org # v6.14+
Signed-off-by: Guopeng Zhang <zhangguopeng@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
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cpuset_current_node_allowed()
Since prepare_alloc_pages() unconditionally adds __GFP_HARDWALL for the
fast path when cpusets are enabled, the __GFP_HARDWALL check in
cpuset_current_node_allowed() causes the PF_EXITING escape path to be
skipped on the first allocation attempt. This makes it unreachable in
the common case, so dying tasks can get stuck in direct reclaim or even
trigger OOM while trying to exit, despite being allowed to allocate from
any node.
Move the PF_EXITING check before __GFP_HARDWALL so that dying tasks
can allocate memory from any node to exit quickly, even when cpusets
are enabled.
Also update the function comment to reflect the actual behavior of
prepare_alloc_pages() and the corrected check ordering.
Signed-off-by: Chen Wandun <chenwandun@lixiang.com>
Acked-by: Michal Koutný <mkoutny@suse.com>
Acked-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 fixes from Tejun Heo:
- During v6.19, cgroup task unlink was moved from do_exit() to after the
final task switch to satisfy a controller invariant. That left the kernel
seeing tasks past exit_signals() longer than userspace expected, and
several v7.0 follow-ups tried to bridge the gap by making rmdir wait for
the kernel side. None held up.
The latest is an A-A deadlock when rmdir is invoked by the reaper of
zombies whose pidns teardown the rmdir itself is waiting on, which
points at the synchronizing approach being fundamentally wrong.
Take a different approach: drop the wait, leave rmdir's user-visible
side returning as soon as cgroup.procs is empty, and defer the css
percpu_ref kill that drives ->css_offline() until the cgroup is fully
depopulated.
Tagged for stable. Somewhat invasive but contained. The hope is that
fixing forward sticks. If not, the fallback is to revert the entire
chain and rework on the development branch.
Note that this doesn't plug a pre-existing analogous race in
cgroup_apply_control_disable() (controller disable via
subtree_control). Not a regression. The development branch will do
the more invasive restructuring needed for that.
- Documentation update for cgroup-v1 charge-commit section that still
referenced functions removed when the memcg hugetlb try-commit-cancel
protocol was retired.
* tag 'cgroup-for-7.1-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
docs: cgroup-v1: Update charge-commit section
cgroup: Defer css percpu_ref kill on rmdir until cgroup is depopulated
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext
Pull sched_ext fixes from Tejun Heo:
- Fix idle CPU selection returning prev_cpu outside the task's cpus_ptr
when the BPF caller's allowed mask was wider. Stable backport.
- Two opposite-direction gaps in scx_task_iter's cgroup-scoped mode
versus the global mode:
- Tasks past exit_signals() are filtered by the cgroup walk but kept
by global. Sub-scheduler enable abort leaked __scx_init_task()
state. Add a CSS_TASK_ITER_WITH_DEAD flag to cgroup's task
iterator (scx_task_iter is its only user) and use it.
- Tasks past sched_ext_dead() are still returned, tripping
WARN_ON_ONCE() in callers or making them touch torn-down state.
Mark and skip under the per-task rq lock.
* tag 'sched_ext-for-7.1-rc2-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext:
sched_ext: idle: Recheck prev_cpu after narrowing allowed mask
sched_ext: Skip past-sched_ext_dead() tasks in scx_task_iter_next_locked()
cgroup, sched_ext: Include exiting tasks in cgroup iter
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a72f73c4dd9b ("cgroup: Don't expose dead tasks in cgroup") made
css_task_iter_advance() skip exiting tasks so cgroup.procs stays consistent
with waitpid() visibility. Unfortunately, this broke scx_task_iter.
scx_task_iter walks either scx_tasks (global) or a cgroup subtree via
css_task_iter() and the two modes are expected to cover the same set of
tasks. After the above change the cgroup-scoped mode silently skips tasks
past exit_signals() that are still on scx_tasks.
scx_sub_enable_workfn()'s abort path is one of the symptoms: an exiting
SCX_TASK_SUB_INIT task can race past the cgroup iter leaking
__scx_init_task() state. Other iterations share the same gap.
Add CSS_TASK_ITER_WITH_DEAD to opt out of the skip and use it from
scx_task_iter().
Fixes: b0e4c2f8a0f0 ("sched_ext: Implement cgroup subtree iteration for scx_task_iter")
Reported-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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A chain of commits going back to v7.0 reworked rmdir to satisfy the
controller invariant that a subsystem's ->css_offline() must not run while
tasks are still doing kernel-side work in the cgroup.
[1] d245698d727a ("cgroup: Defer task cgroup unlink until after the task is done switching out")
[2] a72f73c4dd9b ("cgroup: Don't expose dead tasks in cgroup")
[3] 1b164b876c36 ("cgroup: Wait for dying tasks to leave on rmdir")
[4] 4c56a8ac6869 ("cgroup: Fix cgroup_drain_dying() testing the wrong condition")
[5] 13e786b64bd3 ("cgroup: Increment nr_dying_subsys_* from rmdir context")
[1] moved task cset unlink from do_exit() to finish_task_switch() so a
task's cset link drops only after the task has fully stopped scheduling.
That made tasks past exit_signals() linger on cset->tasks until their final
context switch, which led to a series of problems as what userspace expected
to see after rmdir diverged from what the kernel needs to wait for. [2]-[5]
tried to bridge that divergence: [2] filtered the exiting tasks from
cgroup.procs; [3] had rmdir(2) sleep in TASK_UNINTERRUPTIBLE for them; [4]
fixed the wait's condition; [5] made nr_dying_subsys_* visible
synchronously.
The cgroup_drain_dying() wait in [3] turned out to be a dead end. When the
rmdir caller is also the reaper of a zombie that pins a pidns teardown (e.g.
host PID 1 systemd reaping orphan pids that were re-parented to it during
the same teardown), rmdir blocks in TASK_UNINTERRUPTIBLE waiting for those
pids to free, the pids can't free because PID 1 is the reaper and it's stuck
in rmdir, and the system A-A deadlocks. No internal lock ordering breaks
this; the wait itself is the bug.
The css killing side that drove the original reorder, however, can be made
cleanly asynchronous: ->css_offline() is already async, run from
css_killed_work_fn() driven by percpu_ref_kill_and_confirm(). The fix is to
make that chain start only after all tasks have left the cgroup. rmdir's
user-visible side then returns as soon as cgroup.procs and friends are
empty, while ->css_offline() still runs only after the cgroup is fully
drained.
Verified by the original reproducer (pidns teardown + zombie reaper, runs
under vng) which hangs vanilla and succeeds here, and by per-commit
deterministic repros for [2], [3], [4], [5] with a boot parameter that
widens the post-exit_signals() window so each state is reliably reachable.
Some stress tests on top of that.
cgroup_apply_control_disable() has the same shape of pre-existing race:
when a controller is disabled via subtree_control, kill_css() ran
synchronously while tasks past exit_signals() could still be linked to
the cgroup's csets, and ->css_offline() could fire before they drained.
This patch preserves the existing synchronous behavior at that call site
(kill_css_sync() + kill_css_finish() back-to-back) and a follow-up patch
will defer kill_css_finish() there using a per-css trigger.
This seems like the right approach and I don't see problems with it. The
changes are somewhat invasive but not excessively so, so backporting to
-stable should be okay. If something does turn out to be wrong, the fallback
is to revert the entire chain ([1]-[5]) and rework in the development branch
instead.
v2: Pin cgrp across the deferred destroy work with explicit
cgroup_get()/cgroup_put() around queue_work() and the work_fn. v1
wasn't actually broken (ordered cgroup_offline_wq + queue_work order
in cgroup_task_dead() saved it) but the explicit ref removes the
dependency on those non-obvious invariants. Also note the
pre-existing cgroup_apply_control_disable() race in the description;
a follow-up will defer kill_css_finish() there.
Fixes: 1b164b876c36 ("cgroup: Wait for dying tasks to leave on rmdir")
Cc: stable@vger.kernel.org # v7.0+
Reported-and-tested-by: Martin Pitt <martin@piware.de>
Link: https://lore.kernel.org/all/afHNg2VX2jy9bW7y@piware.de/
Link: https://lore.kernel.org/all/35e0670adb4abeab13da2c321582af9f@kernel.org/
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo:
- Fix UAF race in psi pressure_write() against cgroup file release by
extending cgroup_mutex coverage and ordering of->priv access after
cgroup_kn_lock_live()
- Fix integer overflow in rdmacg_try_charge() when usage equals INT_MAX
by performing the increment in s64
- Fix asymmetric DL bandwidth accounting on cpuset attach rollback by
recording the CPU used by dl_bw_alloc() so cancel_attach() returns
the reservation to the same root domain
- Fix nr_dying_subsys_* race that briefly showed 0 in cgroup.stat after
rmdir by incrementing from kill_css() instead of offline_css()
- Typo fix in cgroup-v2 documentation
* tag 'cgroup-for-7.1-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
docs: cgroup: fix typo 'protetion' -> 'protection'
cgroup: Increment nr_dying_subsys_* from rmdir context
cgroup/cpuset: record DL BW alloc CPU for attach rollback
cgroup/rdma: fix integer overflow in rdmacg_try_charge()
sched/psi: fix race between file release and pressure write
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Incrementing nr_dying_subsys_* in offline_css(), which is executed by
cgroup_offline_wq worker, leads to a race where user can see the value
to be 0 if he reads cgroup.stat after calling rmdir and before the worker
executes. This makes the user wrongly expect resources released by the
removed cgroup to be available for a new assignment.
Increment nr_dying_subsys_* from kill_css(), which is called from the
cgroup_rmdir() context.
Fixes: ab0312526867 ("cgroup: Show # of subsystem CSSes in cgroup.stat")
Signed-off-by: Petr Malat <oss@malat.biz>
Signed-off-by: Tejun Heo <tj@kernel.org>
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Replace the hand-rolled strsep/strcmp/match_string parsing in
rdmacg_resource_set_max() with a match_table_t and match_token()
pattern, following the convention used by user_proactive_reclaim()
and ioc_cost_model_write().
The old strncmp(value, RDMACG_MAX_STR, strlen(value)) also had two
bugs that are fixed by this refactor:
- It matched "ma" as "max" because strncmp only compared the
shorter strlen(value) bytes.
- It silently accepted "hca_handle=" (empty value) as "max"
because strncmp with n=0 always returns 0.
The match_token() approach also robustly handles extra whitespace in
the input by splitting on " \t\n" and skipping empty tokens.
Suggested-by: "Michal Koutný" <mkoutny@suse.com>
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Pull more MM updates from Andrew Morton:
- "Eliminate Dying Memory Cgroup" (Qi Zheng and Muchun Song)
Address the longstanding "dying memcg problem". A situation wherein a
no-longer-used memory control group will hang around for an extended
period pointlessly consuming memory
- "fix unexpected type conversions and potential overflows" (Qi Zheng)
Fix a couple of potential 32-bit/64-bit issues which were identified
during review of the "Eliminate Dying Memory Cgroup" series
- "kho: history: track previous kernel version and kexec boot count"
(Breno Leitao)
Use Kexec Handover (KHO) to pass the previous kernel's version string
and the number of kexec reboots since the last cold boot to the next
kernel, and print it at boot time
- "liveupdate: prevent double preservation" (Pasha Tatashin)
Teach LUO to avoid managing the same file across different active
sessions
- "liveupdate: Fix module unloading and unregister API" (Pasha
Tatashin)
Address an issue with how LUO handles module reference counting and
unregistration during module unloading
- "zswap pool per-CPU acomp_ctx simplifications" (Kanchana Sridhar)
Simplify and clean up the zswap crypto compression handling and
improve the lifecycle management of zswap pool's per-CPU acomp_ctx
resources
- "mm/damon/core: fix damon_call()/damos_walk() vs kdmond exit race"
(SeongJae Park)
Address unlikely but possible leaks and deadlocks in damon_call() and
damon_walk()
- "mm/damon/core: validate damos_quota_goal->nid" (SeongJae Park)
Fix a couple of root-only wild pointer dereferences
- "Docs/admin-guide/mm/damon: warn commit_inputs vs other params race"
(SeongJae Park)
Update the DAMON documentation to warn operators about potential
races which can occur if the commit_inputs parameter is altered at
the wrong time
- "Minor hmm_test fixes and cleanups" (Alistair Popple)
Bugfixes and a cleanup for the HMM kernel selftests
- "Modify memfd_luo code" (Chenghao Duan)
Cleanups, simplifications and speedups to the memfd_lou code
- "mm, kvm: allow uffd support in guest_memfd" (Mike Rapoport)
Support for userfaultfd in guest_memfd
- "selftests/mm: skip several tests when thp is not available" (Chunyu
Hu)
Fix several issues in the selftests code which were causing breakage
when the tests were run on CONFIG_THP=n kernels
- "mm/mprotect: micro-optimization work" (Pedro Falcato)
A couple of nice speedups for mprotect()
- "MAINTAINERS: update KHO and LIVE UPDATE entries" (Pratyush Yadav)
Document upcoming changes in the maintenance of KHO, LUO, memfd_luo,
kexec, crash, kdump and probably other kexec-based things - they are
being moved out of mm.git and into a new git tree
* tag 'mm-stable-2026-04-18-02-14' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (121 commits)
MAINTAINERS: add page cache reviewer
mm/vmscan: avoid false-positive -Wuninitialized warning
MAINTAINERS: update Dave's kdump reviewer email address
MAINTAINERS: drop include/linux/liveupdate from LIVE UPDATE
MAINTAINERS: drop include/linux/kho/abi/ from KHO
MAINTAINERS: update KHO and LIVE UPDATE maintainers
MAINTAINERS: update kexec/kdump maintainers entries
mm/migrate_device: remove dead migration entry check in migrate_vma_collect_huge_pmd()
selftests: mm: skip charge_reserved_hugetlb without killall
userfaultfd: allow registration of ranges below mmap_min_addr
mm/vmstat: fix vmstat_shepherd double-scheduling vmstat_update
mm/hugetlb: fix early boot crash on parameters without '=' separator
zram: reject unrecognized type= values in recompress_store()
docs: proc: document ProtectionKey in smaps
mm/mprotect: special-case small folios when applying permissions
mm/mprotect: move softleaf code out of the main function
mm: remove '!root_reclaim' checking in should_abort_scan()
mm/sparse: fix comment for section map alignment
mm/page_io: use sio->len for PSWPIN accounting in sio_read_complete()
selftests/mm: transhuge_stress: skip the test when thp not available
...
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