Recent optimizations of sd->shared assignment moved to allocating a
single instance of per-CPU sched_domain_shared objects per s_data.
Recent optimizations to select_idle_capacity() moved the sd->shared
assignments to "sd_asym" domain when ASYM_CPUCAPACITY is detected but
cache-aware scheduling mandates the presence of "sd_llc_shared" to
compute and cache per-LLC statistics.
Use an "alloc_flags" union in sched_domain_shared to claim a
sched_domain_shared object per sched_domain. Allocation starts searching
for an available / matching sched_domain_shared instance from the first
CPU of sched_domain_span(sd) (sd can be sd_llc, or sd_asym). If the
shared object is claimed by another domain, the instance corresponding
to next CPU in the domain span is explored until a matching / available
instance is found.
In case of a single CPU in sched_domain_span(), the domain will be
degenerated and a temporary overlap of ->shared objects across different
domains is acceptable.
"alloc_flags" forms a union with "nr_idle_scan" and the stale flags are
left as is when the sd->shared is published. The expectation is for the
first load balancing instance to correct the value just like the current
behavior, except the initial value is no longer 0.
Originally-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Andrea Righi <arighi@nvidia.com>
RT migration is done aggressively. When a CPU schedules out a high
priority RT task for a lower priority task, it will look to see if there's
any RT tasks that are waiting to run on another CPU that is of higher
priority than the task this CPU is about to run. If it finds one, it will
pull that task over to the CPU and allow it to run there instead.
Normally, this pulling is done by looking at the RT overloaded mask (rto)
which contains all the CPUs in the scheduler domain with RT tasks that are
waiting to run due to a higher priority RT task currently running on their
CPU. The CPU that is about to schedule a lower priority task will grab the
rq lock of the overloaded CPU and move the RT task from that CPU's runqueue
to the local one and schedule the higher priority RT task.
This caused issues when a lot of CPUs would schedule a lower priority task
at the same time. They would all try to grab the same runqueue lock of
the CPU with the overloaded RT tasks. Only the first CPU that got in will
get that task. All the others would wait until they got the runqueue lock
and see there's nothing to pull and do nothing. On systems with lots of
CPUs, this caused a large latency (up to 500us) which is beyond what
PREEMPT_RT is to allow.
The solution to that was to create an RT_PUSH_IPI logic. When any CPU
wanted to pull a task, instead of grabbing the runqueue lock of the
overloaded CPU, it would start by sending an IPI to the overloaded CPU,
and that IPI handler would have the CPU with the waiting RT task do a push
instead. Then that handler would send an IPI to the next CPU with
overloaded RT tasks, and so on. Note, after the first CPU starts this
process, if another CPU wanted to do a pull, it would see that the process
has already begun and would only increment a counter to have the IPIs
continue again.
The RT_PUSH_IPI solved the latency problem with PREEMPT_RT but could cause
a new issue with non PREEMPT_RT. Namely, softirqs run in a threaded
context on PREEMPT_RT but they can run in an interrupt context in non-RT.
If an IPI lands on a CPU that has just woken up multiple RT tasks and the
current CPU is running a non RT or a low priority RT task, instead of
doing a push, it would simply do a schedule on that CPU. But if a softirq
was also executing on this CPU, the schedule would need to wait until the
softirq finished. Until then, the CPU would still be considered overloaded
as there are RT tasks still waiting to run on it.
A live lock occurred on a workload that was doing heavy networking traffic
on a large machine where the softirqs would run 500us out of 750us. And it
would also be waking up RT tasks, causing the RT pull logic to be
constantly executed.
When a softirq triggered on a CPU with RT tasks queued but not running
yet, and the other CPUs would see this CPU as being overloaded, they would
send an IPI over to it. The CPU would notice that the waiting RT tasks are
of higher priority than the currently running task and simply schedule
that CPU instead. But because the softirq was executing, before it could
schedule, it would receive another IPI to do the same. The amount of IPIs
would slow down the currently running softirq so much that before it could
return back to task context, it would execute another softirq never
allowing the CPU to schedule. This live locked that CPU.
As RT_PUSH_IPI was created to help PREEMPT_RT, make it default off if
PREEMPT_RT is not enabled.
Fixes: b6366f048e ("sched/rt: Use IPI to trigger RT task push migration instead of pulling")
Closes: https://lore.kernel.org/all/20260506235716.2530720-1-tj@kernel.org/
Reported-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260515103740.25ccbed8@gandalf.local.home
K Prateek noticed we weren't setting the rq->next_class in
proxy_resched_idle(), when I was debugging an issue seen with
CONFIG_SCHED_PROXY_EXEC and some of Peter's new patches, and
suggested this fix.
So set rq->next_class when we temporarily switch the donor to
idle, so we don't accidentally call wakeup_preempt_fair()
with idle as the donor.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260514234732.3170197-1-jstultz@google.com
Add to select_idle_capacity() the same SIS_UTIL-controlled idle-scan
mechanism, already used by select_idle_cpu(): when sched_feat(SIS_UTIL)
is enabled and the LLC domain has sched_domain_shared data, derive the
per-attempt scan limit from sd->shared->nr_idle_scan.
That bounds the walk on large LLCs: once nr_idle_scan is exhausted,
return the best CPU seen so far. The early exit is gated on
!has_idle_core so an active idle-core search (SMT with idle cores
reported by test_idle_cores()) isn't cut short before it gets a chance
to find one.
Co-developed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20260509180955.1840064-6-arighi@nvidia.com
When SD_ASYM_CPUCAPACITY load balancing considers pulling a misfit task,
capacity_of(dst_cpu) can overstate available compute if the SMT sibling is
busy: the core does not deliver its full nominal capacity.
If SMT is active and dst_cpu is not on a fully idle core, skip this
destination so we do not migrate a misfit expecting a capacity upgrade we
cannot actually provide.
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20260509180955.1840064-5-arighi@nvidia.com
On systems with asymmetric CPU capacity (e.g., ACPI/CPPC reporting
different per-core frequencies), the wakeup path uses
select_idle_capacity() and prioritizes idle CPUs with higher capacity
for better task placement. However, when those CPUs belong to SMT cores,
their effective capacity can be much lower than the nominal capacity
when the sibling thread is busy: SMT siblings compete for shared
resources, so a "high capacity" CPU that is idle but whose sibling is
busy does not deliver its full capacity. This effective capacity
reduction cannot be modeled by the static capacity value alone.
Introduce SMT awareness in the asym-capacity idle selection policy: when
SMT is active, always prefer fully-idle SMT cores over partially-idle
ones.
Prioritizing fully-idle SMT cores yields better task placement because
the effective capacity of partially-idle SMT cores is reduced; always
preferring them when available leads to more accurate capacity usage on
task wakeup.
On an SMT system with asymmetric CPU capacities (NVIDIA Vera Rubin),
SMT-aware idle selection has been shown to improve throughput by around
15-18% over NO_ASYM mainline and by around 60% over ASYM mainline, for
CPU-bound workloads (NVBLAS) running an amount of tasks equal to the
amount of SMT cores.
Reported-by: Felix Abecassis <fabecassis@nvidia.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260511142502.3873984-1-arighi@nvidia.com
On asymmetric CPU capacity systems, the wakeup path uses
select_idle_capacity(), which scans the span of sd_asym_cpucapacity
rather than sd_llc.
The has_idle_cores hint however lives on sd_llc->shared, so the
wakeup-time read of has_idle_cores operates on an LLC-scoped blob while
the actual scan/decision spans the asym domain; nr_busy_cpus also lives
in the same shared sched_domain data, but it's never used in the asym
CPU capacity scenario.
Therefore, move the sched_domain_shared object to sd_asym_cpucapacity
whenever the CPU has a SD_ASYM_CPUCAPACITY_FULL ancestor and that
ancestor is non-overlapping (i.e., not built from SD_NUMA). In that case
the scope of has_idle_cores matches the scope of the wakeup scan.
Fall back to attaching the shared object to sd_llc in three cases:
1) plain symmetric systems (no SD_ASYM_CPUCAPACITY_FULL anywhere);
2) CPUs in an exclusive cpuset that carves out a symmetric capacity
island: has_asym is system-wide but those CPUs have no
SD_ASYM_CPUCAPACITY_FULL ancestor in their hierarchy and follow
the symmetric LLC path in select_idle_sibling();
3) exotic topologies where SD_ASYM_CPUCAPACITY_FULL lands on an
SD_NUMA-built domain. init_sched_domain_shared() keys the shared
blob off cpumask_first(span), which on overlapping NUMA domains
would alias unrelated spans onto the same blob. Keep the shared
object on the LLC there; select_idle_capacity() gracefully skips
the has_idle_cores preference when sd->shared is NULL.
While at it, also rename the per-CPU sd_llc_shared to sd_balance_shared,
as it is no longer strictly tied to the LLC.
Co-developed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20260516055850.1345932-1-arighi@nvidia.com
nohz_balancer_kick() is reached from sched_balance_trigger(), which is
called from sched_tick(). sched_tick() runs with IRQs disabled, so the
additional rcu_read_lock/unlock() used around sched_domain accesses in
this path is redundant. Rely on the existing IRQ-disabled context (and
the rcu_dereference_all() checking) instead.
The same applies to set_cpu_sd_state_idle(), called from the idle entry
path with IRQs disabled, and to set_cpu_sd_state_busy(), reachable via
nohz_balance_exit_idle() from two contexts: nohz_balancer_kick() (IRQs
disabled, as above) and sched_cpu_deactivate() (the CPUHP_AP_ACTIVE
teardown, which runs under cpus_write_lock(), so it cannot race with
sched-domain rebuilds). In both cases the rcu_dereference_all()
validation is sufficient.
No functional change intended.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20260509180955.1840064-2-arighi@nvidia.com
There is a use of sched_smt_active() and explicit use of sched_smt_present.
Remove the explicit usage for better code maintenance and readability.
Note that this differs slightly for update_idle_core. It used to call
static_branch_unlikely earlier and now it will call static_branch_likely.
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://patch.msgid.link/20260515172456.542799-5-sshegde@linux.ibm.com
For fastpaths such as wakeup and load balance even minimal code additions
can add up. is_core_idle is accessed during load balance.
Other callsites of is_core_idle make sched_smt_active() check first.
Make the same check in should_we_balance.
Rest of access to cpu_smt_mask isn't in fastpath.
Note: Remove the stale comment above is_core_idle. Enqueue methods
of fair aren't close to it anymore.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://patch.msgid.link/20260515172456.542799-4-sshegde@linux.ibm.com
Now, that cpu_smt_mask is defined as cpumask_of(cpu) for
CONFIG_SCHED_SMT=n, it is possible to get rid of the ifdeffery.
Effectively,
- This makes sched_smt_present is defined always
- cpumask_weight(cpumask_of(cpu)) == 1. So sched_smt_present_inc/dec
will never enable the sched_smt_present. Which is expected.
- Paths that were compile-time eliminated become runtime guarded
using static keys.
- Defines set_idle_cores, test_idle_cores, etc which could likely benefit
the CONFIG_SCHED_SMT=n systems to use the same optimizations within the
LLC at wakeups.
- This will expose sched_smt_present symbol for CONFIG_SCHED_SMT=n.
Likely not a concern.
- There is a bloat of code CONFIG_SCHED_SMT=n. (NR_CPUS=2048)
add/remove: 24/18 grow/shrink: 26/28 up/down: 6396/-3188 (3208)
Total: Before=30629880, After=30633088, chg +0.01%
- No code bloat for CONFIG_SCHED_SMT=y, which is expected.
- Add comments around stop_core_cpuslocked on why ifdefs are not
removed.
- This leaves the remaining uses of CONFIG_SCHED_SMT mainly for
topology building bits which has a policy based decision.
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Phil Auld <pauld@redhat.com>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Acked-by: Tejun Heo <tj@kernel.org>
Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260515172456.542799-3-sshegde@linux.ibm.com
Commit 77baa5bafc ("sched/cputime: Fix mul_u64_u64_div_u64() precision
for cputime") added a clamp in cputime_adjust():
if (unlikely(stime > rtime))
stime = rtime;
The justification was that mul_u64_u64_div_u64() could over-approximate
on some architectures (notably arm64 and the old 32-bit fallback), so
the mathematically impossible stime > rtime was nevertheless reachable
and would underflow utime = rtime - stime.
That premise no longer holds. Commit b29a62d87c ("mul_u64_u64_div_u64:
make it precise always") replaced the fallback implementation with an
exact 128-bit long division, and the x86_64 inline asm already produced
exact results. The helper now returns the mathematically correct
floor(a*b/d) on every architecture, so stime <= rtime is guaranteed by
stime <= stime + utime and the clamp is dead code.
Remove it along with its stale comment.
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260514202629.673539-1-nico@fluxnic.net
Set the default total bandwidth for SCHED_DEADLINE tasks and servers
to ONE. FIFO/RR tasks are already throttled by fair-servers and
ext-servers, and the sysctl_sched_rt_runtime parameter now only
defines the total bw that is allowed to deadline entities.
Signed-off-by: Yuri Andriaccio <yurand2000@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260430213835.62217-22-yurand2000@gmail.com
sched_cache_present is a global static key, but build_sched_domains()
is called per partition from the "Build new domains" loop in
partition_sched_domains_locked(). Each call unconditionally sets the
key based solely on the has_multi_llcs local variable for that partition.
The call to the last partition set the value even when there
are previous partitions with multiple LLCs.
If partition A (multi-LLC) is built first, the key is enabled. Then
when partition B (single-LLC) is built, the key is disabled. The
multi-LLC partition A is still active but the key is now off.
Fix it by doing a similar thing as sched_energy_present: check the
multi-LLCs during the iteration over all the partitions rather than
checking it on a single partition.
This bug was reported by sashiko.
Fixes: d59f4fd1d3 ("sched/cache: Enable cache aware scheduling for multi LLCs NUMA node")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/c541af2547d54509fbfd3b3a1e8072e2e5c7ff68.1778703694.git.tim.c.chen@linux.intel.com
If there are multiple LLCs in the system, cache aware scheduling
should be enabled. However, there is a corner case where, if there
is a single NUMA node and a single LLC per node, cache aware
scheduling will be turned on in the current implementation -
because at this moment, the parent domain has not yet been
degenerated, and it is possible that the current domain has the
same cpu span as its parent. There is no need to turn cache aware
scheduling on in this scenario.
Fix it by iterating the parent domains to find a domain that is
a superset of the current sd_llc, so that later, after the duplicated
parent domains have been degenerated, cache aware scheduling will
take effect.
For example, the expected behavior would be:
2 sockets, 1 LLC per socket: MC span=0-3, PKG span=0-7, has_multi_llcs=true
1 socket, 2 LLCs per socket: MC span=0-3, PKG span=0-7, has_multi_llcs=true
2 sockets, 2 LLCs per socket: MC span=0-3, PKG span=0-7, has_multi_llcs=true
1 socket, 1 LLC per socket: MC span=0-3, PKG span=0-3, has_multi_llcs=false
This bug was reported by sashiko.
Fixes: d59f4fd1d3 ("sched/cache: Enable cache aware scheduling for multi LLCs NUMA node")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/6328a8a7f40925cec2a712d81ee58128a4c4444a.1778703694.git.tim.c.chen@linux.intel.com
sched_cache_active_set_unlocked() checks hardware support without
locks:
static void sched_cache_active_set(bool locked)
{
/* hardware does not support */
if (!static_branch_likely(&sched_cache_present)) {
_sched_cache_active_set(false, locked);
return;
}
...
If build_sched_domains() runs concurrently during CPU hotplug,
it can disable sched_cache_present under sched_domains_mutex
and the CPU hotplug lock. If a debugfs write thread evaluates
sched_cache_present as true right before that, and then blocks
or gets preempted, it might proceed to enable sched_cache_active
after the hardware support has been marked as absent. Make it
safer by acquiring cpus_read_lock() and sched_domains_mutex_lock()
when the user changes sched_cache_active via debugfs.
This bug was reported by sashiko.
Fixes: 067a313581 ("sched/cache: Allow the user space to turn on and off cache aware scheduling")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/9afddf439687f04bb56b46625bd9f153eb8abad5.1778703694.git.tim.c.chen@linux.intel.com
There is a race condition that, after a task is enqueued
on a runqueue, task_llc(p) may change due to CPU hotplug,
because the llc_id is dynamically allocated and adjusted
at runtime.
Therefore, checking task_llc(p) to determine whether the
task is being dequeued from its preferred LLC is unreliable
and can cause inconsistent values.
To fix this problem, record whether p is enqueued on its
preferred LLC, in order to pair with account_llc_dequeue()
to maintain a consistent nr_pref_llc_running per runqueue.
This bug was reported by sashiko, and the solution was once
suggested by Prateek.
Fixes: 46afe3af7e ("sched/cache: Track LLC-preferred tasks per runqueue")
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/0c8c6a1571d66792a4d2ff0103ba3cc13e059046.1778703694.git.tim.c.chen@linux.intel.com
mm->sc_stat.cpu is written by task_cache_work() and could be read
locklessly by several functions on other CPUs. Use READ_ONCE and
WRITE_ONCE on mm->sc_stat.cpu access and write to prevent inconsistent
values from compiler optimizations when there are multiple accesses.
For example in get_pref_llc(), if the writer updated the field between
two compiler-generated loads, the validation (e.g., cpu != -1) and
subsequent use (e.g., llc_id(cpu)) could operate on different values,
allowing a negative CPU ID to be used as an index.
Leave plain write in mm_init_sched(), where the mm is not
yet visible to other CPUs.
This bug was reported by sashiko.
Fixes: 47d8696b95 ("sched/cache: Assign preferred LLC ID to processes")
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/63ea494f12efcf265d7134400a06cd75d7f2c310.1778703694.git.tim.c.chen@linux.intel.com
Introduce a set of debugfs knobs to control how aggressively the
cache aware scheduling does the task aggregation.
(1) aggr_tolerance
With sched_cache enabled, the scheduler uses a process's footprint
as a proxy for its LLC footprint to determine if aggregating tasks
on the preferred LLC could cause cache contention. If the footprint
exceeds the LLC size, aggregation is skipped. Since the kernel
cannot efficiently track per-task cache usage (resctrl is
user-space only), userspace can provide a more accurate hint.
Introduce /sys/kernel/debug/sched/llc_balancing/aggr_tolerance to
let users control how strictly footprint limits aggregation. Values
range from 0 to 100:
- 0: Cache-aware scheduling is disabled.
- 1: Strict; tasks with footprint larger than LLC size are skipped.
- >=100: Aggressive; tasks are aggregated regardless of footprint.
For example, with a 32MB L3 cache:
- aggr_tolerance=1 -> tasks with footprint > 32MB are skipped.
- aggr_tolerance=99 -> tasks with footprint > 784GB are skipped
(784GB = (1 + (99 - 1) * 256) * 32MB).
Similarly, /sys/kernel/debug/sched/llc_balancing/aggr_tolerance also
controls how strictly the number of active threads is considered when
doing cache aware load balance. The number of SMTs is also considered.
High SMT counts reduce the aggregation capacity, preventing excessive
task aggregation on SMT-heavy systems like Power10/Power11.
Yangyu suggested introducing separate aggregation controls for the
number of active threads and memory footprint checks. Since there are
plans to add per-process/task group controls, fine-grained tunables are
deferred to that implementation.
(2) epoch_period, epoch_affinity_timeout,
imb_pct, overaggr_pct are also turned into tunables.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Suggested-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Suggested-by: Tingyin Duan <tingyin.duan@gmail.com>
Suggested-by: Jianyong Wu <jianyong.wu@outlook.com>
Suggested-by: Yangyu Chen <cyy@cyyself.name>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Tingyin Duan <tingyin.duan@gmail.com>
Link: https://patch.msgid.link/1c62cc060ba2b33d7b1f0ed98b3390128edbae93.1778703694.git.tim.c.chen@linux.intel.com
Prateek and Tingyin reported that memory-intensive workloads (such as
stream) can saturate memory bandwidth and caches on the preferred LLC
when sched_cache aggregates too many threads.
To mitigate this, estimate a process's memory footprint by comparing
its NUMA balancing fault statistics to the size of the LLC. If the
footprint exceeds the LLC size, skip cache-aware scheduling.
Note that footprint is only an approximation of the memory footprint,
since the kernel lacks suitable metrics to estimate the real working
set. If a user-provided hint is available in the future, it would be
more accurate. A later patch will allow users to provide a hint to
adjust this threshold.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Vern Hao <vernhao@tencent.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Tingyin Duan <tingyin.duan@gmail.com>
Link: https://patch.msgid.link/95cf64a385bcc12f18dcebe9d59e8d3ba8bb318f.1778703694.git.tim.c.chen@linux.intel.com
For a single thread, the current wakeup path tends to place it
on the same LLC where it was previously running with cache-hot
data. There is no need to enable cache-aware scheduling for
single-threaded processes for the following reasons:
1. Cache-aware scheduling primarily benefits multi-threaded
processes where threads share data. Single-threaded processes
typically have no inter-thread data sharing and thus gain little.
2. Enabling it incurs the additional overhead of tracking the
thread's residency in the LLCs.
3. Bypassing single-threaded processes avoids excessive
concentration of such tasks on a single LLC.
Nevertheless, this check can be omitted if users explicitly
provide hints for such single-threaded workloads where different
processes have shared memory, e.g., via prctl() or other interfaces
to be added in the future.
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Tingyin Duan <tingyin.duan@gmail.com>
Link: https://patch.msgid.link/8a59a13aa58fdb48e410ecb2aabd97fe3ea5d256.1778703694.git.tim.c.chen@linux.intel.com
A performance regression was observed by Prateek when running hackbench
with many threads per process (high fd count). To avoid this, processes
with a large number of active threads are excluded from cache-aware
scheduling.
With sched_cache enabled, record the number of active threads in each
process during the periodic task_cache_work(). While iterating over
CPUs, if the currently running task belongs to the same process as the
task that launched task_cache_work(), increment the active thread count.
If the number of active threads within the process exceeds the number
of Cores (divided by the SMT number) in the LLC, do not enable
cache-aware scheduling. However, on systems with a smaller number of
CPUs within 1 LLC, like Power10/Power11 with SMT4 and an LLC size of 4,
this check effectively disables cache-aware scheduling for any process.
One possible solution suggested by Peter is to use an LLC-mask instead
of a single LLC value for preference. Once there are a 'few' LLCs as
preference, this constraint becomes a little easier. It could be an
enhancement in the future.
For users who wish to perform task aggregation regardless, a debugfs knob
is provided for tuning in a subsequent change.
Suggested-by: K Prateek Nayak <kprateek.nayak@amd.com>
Suggested-by: Aaron Lu <ziqianlu@bytedance.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Co-developed-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Tingyin Duan <tingyin.duan@gmail.com>
Link: https://patch.msgid.link/d076cd21a8e6c6341d1e2d927e118db770ebb650.1778703694.git.tim.c.chen@linux.intel.com
The wrapper functions __trace_set_current_state() and
__trace_set_need_resched() allow the tracepoints to be called from code
outside sched/core.c, those calls are already guarded by a
tracepoint_enabled(<tp>) so there is no need to repeat this check once
again inside the call using trace_<tp>().
Use the new trace_call__<tp>() API to directly call the tracepoint
without check. Those helper functions must be called after the
appropriate check.
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260429094227.34087-1-gmonaco@redhat.com
Pull locking fix from Ingo Molnar:
"Fix lockup in requeue-PI during signal/timeout wakeups, by Sebastian
Andrzej Siewior"
* tag 'locking-urgent-2026-05-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
futex: Prevent lockup in requeue-PI during signal/ timeout wakeup
Pull scheduler fixes from Ingo Molnar:
- Fix the delayed dequeue negative lag increase fix in the
fair scheduler (Peter Zijlstra)
- Fix wakeup_preempt_fair() to do proper delayed dequeue
(Vincent Guittot)
- Clear sched_entity::rel_deadline when initializing
forked entities, which bug can cause all tasks to be
EEVDF-ineligible, causing a NULL pointer dereference
crash in pick_next_entity() (Zicheng Qu)
* tag 'sched-urgent-2026-05-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/fair: Clear rel_deadline when initializing forked entities
sched/fair: Fix wakeup_preempt_fair() vs delayed dequeue
sched/fair: Fix the negative lag increase fix
Currently need_futex_hash_allocate_default() depends on strict pthread
semantics, abusing CLONE_THREAD. This breaks the non-concurrency
assumptions when doing the mm->futex_ref pcpu allocations, leading to
bugs[0] when sharing the mm in other ways; ie:
BUG: KASAN: slab-use-after-free in futex_hash_put
... where the +1 bias can end up on a percpu counter that mm->futex_ref
no longer points at.
Loosen the check to cover any CLONE_VM clone, except vfork(). Excluding
vfork keeps the existing paths untouched (no overhead), and we can't
race in the first place: either the parent is suspended and the child
runs alone, or mm->futex_ref is already allocated from an earlier
CLONE_VM.
Link: https://lore.kernel.org/all/CAL_bE8LsmCQ-FAtYDuwbJhOkt9p2wwYQwAbMh=PifC=VsiBM6A@mail.gmail.com/ [0]
Fixes: d9b05321e2 ("futex: Move futex_hash_free() back to __mmput()")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull MM fixes from Andrew Morton:
"20 hotfixes. All are for MM (and for MMish maintainers). 9 are
cc:stable and the remainder are for post-7.0 issues or aren't deemed
suitable for backporting.
There are two DAMON series from SeongJae Park which address races
which could lead to use-after-free errors, and avoid the possibility
of presenting stale parameter values to users"
* tag 'mm-hotfixes-stable-2026-04-30-15-39' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
mm: memcontrol: fix rcu unbalance in get_non_dying_memcg_end()
mm/userfaultfd: detect VMA type change after copy retry in mfill_copy_folio_retry()
MAINTAINERS: remove stale kdump project URL
mm/damon/stat: detect and use fresh enabled value
mm/damon/lru_sort: detect and use fresh enabled and kdamond_pid values
mm/damon/reclaim: detect and use fresh enabled and kdamond_pid values
selftests/mm: specify requirement for PROC_MEM_ALWAYS_FORCE=y
mm/damon/sysfs-schemes: protect path kfree() with damon_sysfs_lock
mm/damon/sysfs-schemes: protect memcg_path kfree() with damon_sysfs_lock
MAINTAINERS: update Li Wang's email address
MAINTAINERS, mailmap: update email address for Qi Zheng
MAINTAINERS: update Liam's email address
mm/hugetlb_cma: round up per_node before logging it
MAINTAINERS: fix regex pattern in CORE MM category
mm/vma: do not try to unmap a VMA if mmap_prepare() invoked from mmap()
mm: start background writeback based on per-wb threshold for strictlimit BDIs
kho: fix error handling in kho_add_subtree()
liveupdate: fix return value on session allocation failure
mailmap: update entry for Dan Carpenter
vmalloc: fix buffer overflow in vrealloc_node_align()
Pull tracing fixes from Steven Rostedt:
- Fix inverted check of registering the stats for branch tracing
When calling register_stat_tracer() which returns zero on success and
negative on error, the callers were checking the return of zero as an
error and printing a warning message. Because this was just a normal
printk() message and not a WARN(), it wasn't caught in any testing.
Fix the check to print the warning message when an error actually
happens.
- Fix a typo in a comment in tracepoint.h
- Limit the size of event probes to 3K in size
It is possible to create a dynamic event probe via the tracefs system
that is greater than the max size of an event that the ring buffer
can hold. This basically causes the event to become useless.
Limit the size of an event probe to be 3K as that should be large
enough to handle any dynamic events being created, and fits within
the PAGE_SIZE sub-buffers of the ring buffer.
* tag 'trace-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
tracing/probes: Limit size of event probe to 3K
tracepoint: Fix typo in tracepoint.h comment
tracing: branch: Fix inverted check on stat tracer registration
There currently isn't a max limit an event probe can be. One could make an
event greater than PAGE_SIZE, which makes the event useless because if
it's bigger than the max event that can be recorded into the ring buffer,
then it will never be recorded.
A event probe should never need to be greater than 3K, so make that the
max size. As long as the max is less than the max that can be recorded
onto the ring buffer, it should be fine.
Cc: stable@vger.kernel.org
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Fixes: 93ccae7a22 ("tracing/kprobes: Support basic types on dynamic events")
Link: https://patch.msgid.link/20260428122302.706610ba@gandalf.local.home
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
During wait-requeue-pi (task A) and requeue-PI (task B) the following
race can happen:
Task A Task B
futex_wait_requeue_pi()
futex_setup_timer()
futex_do_wait()
futex_requeue()
CLASS(hb, hb1)(&key1);
CLASS(hb, hb2)(&key2);
*timeout*
futex_requeue_pi_wakeup_sync()
requeue_state = Q_REQUEUE_PI_IGNORE
*blocks on hb->lock*
futex_proxy_trylock_atomic()
futex_requeue_pi_prepare()
Q_REQUEUE_PI_IGNORE => -EAGAIN
double_unlock_hb(hb1, hb2)
*retry*
Task B acquires both hb locks and attempts to acquire the PI-lock of the
top most waiter (task B). Task A is leaving early due to a signal/
timeout and started removing itself from the queue. It updates its
requeue_state but can not remove it from the list because this requires
the hb lock which is owned by task B.
Usually task A is able to swoop the lock after task B unlocked it.
However if task B is of higher priority then task A may not be able to
wake up in time and acquire the lock before task B gets it again.
Especially on a UP system where A is never scheduled.
As a result task A blocks on the lock and task B busy loops, trying to
make progress but live locks the system instead. Tragic.
This can be fixed by removing the top most waiter from the list in this
case. This allows task B to grab the next top waiter (if any) in the
next iteration and make progress.
Remove the top most waiter if futex_requeue_pi_prepare() fails.
Let the waiter conditionally remove itself from the list in
handle_early_requeue_pi_wakeup().
Fixes: 07d91ef510 ("futex: Prevent requeue_pi() lock nesting issue on RT")
Reported-by: Moritz Klammler <Moritz.Klammler@ferchau.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260428103425.dywXyPd3@linutronix.de
Closes: https://lore.kernel.org/all/VE1PR06MB6894BE61C173D802365BE19DFF4CA@VE1PR06MB6894.eurprd06.prod.outlook.com
Pull sched_ext fixes from Tejun Heo:
"The merge window pulled in the cgroup sub-scheduler infrastructure,
and new AI reviews are accelerating bug reporting and fixing - hence
the larger than usual fixes batch:
- Use-after-frees during scheduler load/unload:
- The disable path could free the BPF scheduler while deferred
irq_work / kthread work was still in flight
- cgroup setter callbacks read the active scheduler outside the
rwsem that synchronizes against teardown
Fix both, and reuse the disable drain in the enable error paths so
the BPF JIT page can't be freed under live callbacks.
- Several BPF op invocations didn't tell the framework which runqueue
was already locked, so helper kfuncs that re-acquire the runqueue
by CPU could deadlock on the held lock
Fix the affected callsites, including recursive parent-into-child
dispatch.
- The hardlockup notifier ran from NMI but eventually took a
non-NMI-safe lock. Bounce it through irq_work.
- A handful of bugs in the new sub-scheduler hierarchy:
- helper kfuncs hard-coded the root instead of resolving the
caller's scheduler
- the enable error path tried to disable per-task state that had
never been initialized, and leaked cpus_read_lock on the way
out
- a sysfs object was leaked on every load/unload
- the dispatch fast-path used the root scheduler instead of the
task's
- a couple of CONFIG #ifdef guards were misclassified
- Verifier-time hardening: BPF programs of unrelated struct_ops types
(e.g. tcp_congestion_ops) could call sched_ext kfuncs - a semantic
bug and, once sub-sched was enabled, a KASAN out-of-bounds read.
Now rejected at load. Plus a few NULL and cross-task argument
checks on sched_ext kfuncs, and a selftest covering the new deny.
- rhashtable (Herbert): restore the insecure_elasticity toggle and
bounce the deferred-resize kick through irq_work to break a
lock-order cycle observable from raw-spinlock callers. sched_ext's
scheduler-instance hash is the first user of both.
- The bypass-mode load balancer used file-scope cpumasks; with
multiple scheduler instances now possible, those raced. Move to
per-instance cpumasks, plus a follow-up to skip tasks whose
recorded CPU is stale relative to the new owning runqueue.
- Smaller fixes:
- a dispatch queue's first-task tracking misbehaved when a parked
iterator cursor sat in the list
- the runqueue's next-class wasn't promoted on local-queue
enqueue, leaving an SCX task behind RT in edge cases
- the reference qmap scheduler stopped erroring on legitimate
cross-scheduler task-storage misses"
* tag 'sched_ext-for-7.1-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (26 commits)
sched_ext: Fix scx_flush_disable_work() UAF race
sched_ext: Call wakeup_preempt() in local_dsq_post_enq()
sched_ext: Release cpus_read_lock on scx_link_sched() failure in root enable
sched_ext: Reject NULL-sch callers in scx_bpf_task_set_slice/dsq_vtime
sched_ext: Refuse cross-task select_cpu_from_kfunc calls
sched_ext: Align cgroup #ifdef guards with SUB_SCHED vs GROUP_SCHED
sched_ext: Make bypass LB cpumasks per-scheduler
sched_ext: Pass held rq to SCX_CALL_OP() for core_sched_before
sched_ext: Pass held rq to SCX_CALL_OP() for dump_cpu/dump_task
sched_ext: Save and restore scx_locked_rq across SCX_CALL_OP
sched_ext: Use dsq->first_task instead of list_empty() in dispatch_enqueue() FIFO-tail
sched_ext: Resolve caller's scheduler in scx_bpf_destroy_dsq() / scx_bpf_dsq_nr_queued()
sched_ext: Read scx_root under scx_cgroup_ops_rwsem in cgroup setters
sched_ext: Don't disable tasks in scx_sub_enable_workfn() abort path
sched_ext: Skip tasks with stale task_rq in bypass_lb_cpu()
sched_ext: Guard scx_dsq_move() against NULL kit->dsq after failed iter_new
sched_ext: Unregister sub_kset on scheduler disable
sched_ext: Defer scx_hardlockup() out of NMI
sched_ext: sync disable_irq_work in bpf_scx_unreg()
sched_ext: Fix local_dsq_post_enq() to use task's scheduler in sub-sched
...
init_annotated_branch_stats() and all_annotated_branch_stats() check the
return value of register_stat_tracer() with "if (!ret)", but
register_stat_tracer() returns 0 on success and a negative errno on
failure. The inverted check causes the warning to be printed on every
successful registration, e.g.:
Warning: could not register annotated branches stats
while leaving real failures silent. The initcall also returned a
hard-coded 1 instead of the actual error.
Invert the check and propagate ret so that the warning fires on real
errors and the initcall reports the correct status.
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Link: https://patch.msgid.link/20260420-tracing-v1-1-d8f4cd0d6af1@debian.org
Fixes: 002bb86d8d ("tracing/ftrace: separate events tracing and stats tracing engine")
Signed-off-by: Breno Leitao <leitao@debian.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
scx_flush_disable_work() calls irq_work_sync() followed by
kthread_flush_work() to ensure that the disable kthread work has
fully completed before bpf_scx_unreg() frees the SCX scheduler.
However, a concurrent scx_vexit() (e.g., triggered by a watchdog stall)
creates a race window between scx_claim_exit() and irq_work_queue():
CPU A (scx_vexit (watchdog)) CPU B (bpf_scx_unreg)
---- ----
scx_claim_exit()
atomic_try_cmpxchg(NONE->kind)
stack_trace_save()
vscnprintf()
scx_disable()
scx_claim_exit() -> FAIL
scx_flush_disable_work()
irq_work_sync() // no-op: not queued yet
kthread_flush_work() // no-op: not queued yet
kobject_put(&sch->kobj) -> free %sch
irq_work_queue() -> UAF on %sch
scx_disable_irq_workfn()
kthread_queue_work() -> UAF
The root cause is that CPU B's scx_flush_disable_work() returns after
syncing an irq_work that has not yet been queued, while CPU A is still
executing the code between scx_claim_exit() and irq_work_queue().
Loop until exit_kind reaches SCX_EXIT_DONE or SCX_EXIT_NONE, draining
disable_irq_work and disable_work in each pass. This ensures that any
work queued after the previous check is caught, while also correctly
handling cases where no disable was triggered (e.g., the
scx_sub_enable_workfn() abort path).
Fixes: 510a270554 ("sched_ext: sync disable_irq_work in bpf_scx_unreg()")
Reported-by: https://sashiko.dev/#/patchset/20260424100221.32407-1-icheng%40nvidia.com
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
There are several edge cases (see linked thread) where an IMMED task
can be left lingering on a local DSQ if an RT task swoops in at the
wrong time. All of these edge cases are due to rq->next_class being idle
even after dispatching a task to rq's local DSQ. We should bump
rq->next_class to &ext_sched_class as soon as we've inserted a task into
the local DSQ.
To optimize the common case of rq->next_class == &ext_sched_class,
only call wakeup_preempt() if rq->next_class is below EXT. If next_class
is EXT or above, wakeup_preempt() is a no-op anyway.
This lets us also simplify the preempt_curr() logic a bit since
wakeup_preempt() will call preempt_curr() for us if next_class is
below EXT.
Link: https://lore.kernel.org/all/DHZPHUFXB4N3.2RY28MUEWBNYK@google.com/
Signed-off-by: Kuba Piecuch <jpiecuch@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
A yield-triggered crash can happen when a newly forked sched_entity
enters the fair class with se->rel_deadline unexpectedly set.
The failing sequence is:
1. A task is forked while se->rel_deadline is still set.
2. __sched_fork() initializes vruntime, vlag and other sched_entity
state, but does not clear rel_deadline.
3. On the first enqueue, enqueue_entity() calls place_entity().
4. Because se->rel_deadline is set, place_entity() treats se->deadline
as a relative deadline and converts it to an absolute deadline by
adding the current vruntime.
5. However, the forked entity's deadline is not a valid inherited
relative deadline for this new scheduling instance, so the conversion
produces an abnormally large deadline.
6. If the task later calls sched_yield(), yield_task_fair() advances
se->vruntime to se->deadline.
7. The inflated vruntime is then used by the following enqueue path,
where the vruntime-derived key can overflow when multiplied by the
entity weight.
8. This corrupts cfs_rq->sum_w_vruntime, breaks EEVDF eligibility
calculation, and can eventually make all entities appear ineligible.
pick_next_entity() may then return NULL unexpectedly, leading to a
later NULL dereference.
A captured trace shows the effect clearly. Before yield, the entity's
vruntime was around:
9834017729983308
After yield_task_fair() executed:
se->vruntime = se->deadline
the vruntime jumped to:
19668035460670230
and the deadline was later advanced further to:
19668035463470230
This shows that the deadline had already become abnormally large before
yield_task_fair() copied it into vruntime.
rel_deadline is only meaningful when se->deadline really carries a
relative deadline that still needs to be placed against vruntime. A
freshly forked sched_entity should not inherit or retain this state.
Clear se->rel_deadline in __sched_fork(), together with the other
sched_entity runtime state, so that the first enqueue does not interpret
the new entity's deadline as a stale relative deadline.
Fixes: 82e9d0456e ("sched/fair: Avoid re-setting virtual deadline on 'migrations'")
Analyzed-by: Hui Tang <tanghui20@huawei.com>
Analyzed-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Zicheng Qu <quzicheng@huawei.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260424071113.1199600-1-quzicheng@huawei.com
Similar to how pick_next_entity() must dequeue delayed entities, so too must
wakeup_preempt_fair(). Any delayed task being found means it is eligible and
hence past the 0-lag point, ready for removal.
Worse, by not removing delayed entities from consideration, it can skew the
preemption decision, with the end result that a short slice wakeup will not
result in a preemption.
tip/sched/core tip/sched/core +this patch
cyclictest slice (ms) (default)2.8 8 8
hackbench slice (ms) (default)2.8 20 20
Total Samples | 22559 22595 22683
Average (us) | 157 64( 59%) 59( 8%)
Median (P50) (us) | 57 57( 0%) 58(- 2%)
90th Percentile (us) | 64 60( 6%) 60( 0%)
99th Percentile (us) | 2407 67( 97%) 67( 0%)
99.9th Percentile (us) | 3400 2288( 33%) 727( 68%)
Maximum (us) | 5037 9252(-84%) 7461( 19%)
Fixes: f12e148892 ("sched/fair: Prepare pick_next_task() for delayed dequeue")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260422093400.319251-1-vincent.guittot@linaro.org
Vincent reported that my rework of his original patch lost a little
something.
Specifically it got the return value wrong; it should not compare
against the old se->vlag, but rather against the current value. Since
the thing that matters is if the effective vruntime of an entity is
affected and the thing needs repositioning or not.
Fixes: 059258b0d4 ("sched/fair: Prevent negative lag increase during delayed dequeue")
Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20260423094107.GT3102624%40noisy.programming.kicks-ass.net
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
Fix two error handling issues in kho_add_subtree(), where it doesn't
handle the error path correctly.
1. If fdt_setprop() fails after the subnode has been created, the
subnode is not removed. This leaves an incomplete node in the FDT
(missing "preserved-data" or "blob-size" properties).
2. The fdt_setprop() return value (an FDT error code) is stored
directly in err and returned to the caller, which expects -errno.
Fix both by storing fdt_setprop() results in fdt_err, jumping to a new
out_del_node label that removes the subnode on failure, and only setting
err = 0 on the success path, otherwise returning -ENOMEM (instead of
FDT_ERR_ errors that would come from fdt_setprop).
No user-visible changes. This patch fixes error handling in the KHO
(Kexec HandOver) subsystem, which is used to preserve data across kexec
reboots. The fix only affects a rare failure path during kexec
preparation — specifically when the kernel runs out of space in the
Flattened Device Tree buffer while registering preserved memory regions.
In the unlikely event that this error path was triggered, the old code
would leave a malformed node in the device tree and return an incorrect
error code to the calling subsystem, which could lead to confusing log
messages or incorrect recovery decisions. With this fix, the incomplete
node is properly cleaned up and the appropriate errno value is propagated,
this error code is not returned to the user.
Link: https://lore.kernel.org/20260410-kho_fix_send-v2-1-1b4debf7ee08@debian.org
Fixes: 3dc92c3114 ("kexec: add Kexec HandOver (KHO) generation helpers")
Signed-off-by: Breno Leitao <leitao@debian.org>
Suggested-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Breno Leitao <leitao@debian.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
When session allocation fails during deserialization, the global 'err'
variable was not updated before returning. This caused subsequent calls
to luo_session_deserialize() to incorrectly report success.
Ensure 'err' is set to the error code from PTR_ERR(session). This ensures
that an error is correctly returned to userspace when it attempts to open
/dev/liveupdate in the new kernel if deserialization failed.
Link: https://lore.kernel.org/20260415193738.515491-1-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pratyush Yadav (Google) <pratyush@kernel.org>
Cc: David Matlack <dmatlack@google.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
