Changes in Kconfig.preempt

11260c335ec6071af5543aef73000b28f041c124 - Merge tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext

Thu, 20 Aug 2026 20:01:37 +0200

Merge tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_extPull sched_ext updates from Tejun Heo: "Most of this cycle completes the enqueue-path support for hierarchical sub-scheduling, which makes sub-scheduler support feature complete: a root BPF scheduler can now hand a cgroup subtree over to a nested sub-scheduler together with revocable CPU grants, and the sub-scheduler owns all scheduling decisions for its tasks on those CPUs. Development volume was high and a number of changes plugging holes in the new support landed late in the cycle. Also included are core scheduling fixes that were completed too late for the v7.2 release and are routed through this pull request. Sub-scheduler CPU delegation: - Parent schedulers now grant and revoke per-CPU capabilities (enqueueing, preemption, CPU frequency control) on their children, enforced on every path a scheduler can reach a CPU through. Previously only dispatching could be delegated; this lets sub-schedulers fully schedule their CPUs. - Rescue execution: a task whose scheduler doesn't have access to the CPUs the task needs to run on starved until the watchdog ejected the whole scheduler. The kernel now runs such tasks directly on a small bandwidth budget, turning a scheduler-killing failure into bounded degradation. - Cgroup integration: tasks migrating across a sub-scheduler boundary weren't re-homed to the new owner, causing wrong-scheduler scheduling and a use-after-free. Sub-schedulers now take over their cgroup subtree and receive its cgroup callbacks. - Arena objects now cross the kernel/BPF boundary as typed pointer arguments, translated transparently by the BPF tree's new arena argument support, replacing untyped arguments with manual translation. - scx_qmap now demonstrates full hierarchical sub-scheduling. Other fixes and updates: - Robustness improvements: the abort path is now NMI-safe, fixing deadlocks when errors are raised from NMI context and making hardlockup recovery direct. Reenqueue loops that could monopolize a CPU ahead of the watchdog now eject the offending scheduler, and stalls are blamed on the scheduler actually responsible. - Hardening: BPF-writable arena memory is validated before kernel use, and task slice and vtime writes got explicit synchronization rules, closing corruption vectors open to buggy or malicious schedulers. - Core scheduling: sched_ext dispatching can drop the rq lock inside the core-wide pick, which let interleaving selections corrupt each other's state and hard-hang the machine. The selection now restarts when the lock was released. The task ordering callback was also invoked with its arguments swapped, and the default ordering is updated to work across sub-scheduler boundaries. The fixes are marked for stable. - Other fixes headed for stable: a task init leak on fork failure during enable, tooling compat macros that silently failed to detect newer kernels, and a crash on reenqueueing against a destroyed dispatch queue. - Tooling: scx_pair moves off deprecated callbacks, and the deprecated scx_bpf_cpu_rq() kfunc is removed"* tag 'sched_ext-for-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext: (144 commits) sched_ext: Drop the dead SCX_DEQ_CORE_SCHED_EXEC test in dequeue_task_scx() sched_ext: Make core-sched task ordering hierarchy-aware sched_ext: Use runnable_at for the default core-sched task ordering sched_ext: Fix inverted ops.core_sched_before() invocation sched_ext: Move the config-off sub-cap kfunc stubs into sub.c sched_ext: Rename balance-era identifiers to dispatch terms sched_ext: Drop the stale keep_prev fixup in dispatch_pick() sched_ext: Keep kick_sync waiting on the rq's own CPU sched_ext: Make SCHED_CLASS_EXT select GENERIC_ALLOCATOR sched_ext/scx_flatcg: Fix cvtime true-up on slice expiry sched_ext: Don't BUG_ON a destroyed DSQ in process_deferred_reenq_users sched_ext: Fix scx_bpf_dsq_move_to_local___v2 compat detection sched_ext: Make scx_bpf_events() read the calling scheduler's counters sched_ext: Drop unlocked scx_rq_clock_invalidate() from scx_root_disable() selftests/sched_ext: Fix flaky ddsp failure tests on busy systems selftests/sched_ext: Make numa idle validation race-free sched_ext: Fix scx_bpf_dsq_reenq___compat kfunc extern prototype sched_ext/scx_flatcg: expire cached hweights on weight changes sched_ext: Fix exit_task leak on fork failure during enable sched_ext: fix stale references in doc comments ... List of files: /linux/kernel/Kconfig.preempt

524ab50763af33d65e6e042cf7034cd8f82d437b - sched_ext: Make SCHED_CLASS_EXT select GENERIC_ALLOCATOR

Sat, 15 Aug 2026 11:44:52 +0200

sched_ext: Make SCHED_CLASS_EXT select GENERIC_ALLOCATORkernel/sched/ext/arena.c uses the gen_pool allocator, which is built onlywhen GENERIC_ALLOCATOR is set. SCHED_CLASS_EXT doesn't select it, so onconfigs where nothing else does, the build fails to link: build_policy.o: undefined reference to `gen_pool_create' build_policy.o: undefined reference to `gen_pool_for_each_chunk' build_policy.o: undefined reference to `gen_pool_destroy'Fixes: 9eca087deb0b ("sched_ext: Sub-allocator over kernel-claimed BPF arena pages")Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202608151315.tvN3X0Oq-lkp@intel.com/Closes: https://lore.kernel.org/oe-kbuild-all/202608151632.3p91bTQj-lkp@intel.com/Signed-off-by: Tejun Heo List of files: /linux/kernel/Kconfig.preempt

dfa35434d7f20142fedd7120277b1044a0a2bb64 - Merge tag 'locking-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Tue, 18 Aug 2026 22:07:17 +0200

Merge tag 'locking-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipPull locking updates from Ingo Molnar: "Futexes: - Use runtime constants for futex_hash computation (K Prateek Nayak, Peter Zijlstra) - Optimise the size check get_futex_key() (Sebastian Andrzej Siewior) - Avoid private hash use-after-free on final put (Felix Hoffmann) - Tell kmemleak we're not leaking __futex_queues (Peter Zijlstra) Rust integration updates: - Implement refcounted interrupt disable and SpinLockIrq for Rust (Boqun Feng, Heiko Carstens, Joel Fernandes, Lyude Paul) - Rust sync: add helpers for mb, dma_mb and friends; add generic memory barriers and use LKMM atomics instead of Rust atomics in the revocable code (Gary Guo) - Add abstraction and integrate synchronize_rcu() (Philipp Stanner) Lock debugging: - Add qspinlock contended_release tracepoint (Dmitry Ilvokhin, Peter Zijlstra) - Enable the printing of held locks of remote running tasks and print task CPU (Ingo Molnar) - percpu-rwsem: Annotate intentional data race in readers_active_check() (Sun Shaojie) Misc fixes and updates by Boqun Feng, Peter Zijlstra, Fangrui Song, Naveen Kumar Chaudhary and Thomas Huth"* tag 'locking-core-2026-08-17' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits) rust: sync: Introduce SpinLockIrq::lock_with() and friends rust: sync: Add SpinLockIrq rust: sync: Use super::* in spinlock.rs rust: helper: Add spin_{un,}lock_irq_{enable,disable}() helpers rust: Introduce interrupt module s390/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS arm64: sched/preempt: Enable HAS_SEPARATE_PREEMPT_RESCHED_BITS preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS sched: Avoid signed comparison of preempt_count() in __cant_migrate() sched: Remove the unused preempt_offset parameter of __cant_sleep() locking: Switch to _irq_{disable,enable}() variants in cleanup guards irq: Add KUnit test for refcounted interrupt enable/disable irq,spin_lock: Add counted interrupt disabling/enabling openrisc: Include in smp.h preempt: Introduce __preempt_count_{sub,add}_return() preempt: Introduce HARDIRQ_DISABLE_BITS preempt: Track NMI nesting to separate per-CPU counter futex: Tell kmemleak we're not leaking __futex_queues x86/paravirt: Trace contended_release on unlock tracing/lock: Use TRACE_EVENT_FN() for contended_release ... List of files: /linux/kernel/Kconfig.preempt

3b0e2a22d4086ed7c1294584c4417f7d19f1ac67 - preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITS

Tue, 04 Aug 2026 18:14:32 +0200

preempt: Introduce HAS_SEPARATE_PREEMPT_RESCHED_BITSWith the changes that enable preempt count to track IRQ disablingnesting, we don't have enough bits in 32-bit preempt countimplementation, as a result we move NMI nesting bits out of the 32-bitpreempt count. However on the architectures that can support 64-bitpreempt count implementation, we can keep the NMI nesting bits in the32-bit preempt count and avoid maintaining NMI nesting bits outside ofthe same cache line.Therefore HAS_SEPARATE_PREEMPT_RESCHED_BITS is introduced to allowarchitectures to select this. Note that under this Kconfig, preemptcount is maintained in a 64-bit word however preempt_count() stillremains as an int because all the effective bits still fit in(previously we mask out NEED_RESCHED bit in preempt_count()). Thisshould make no functional changes for existing preempt_count() users.Enable this for x86_64 along with the introduction of the Kconfig.[boqun: Undo the __preempt_count_{add,sub}() optimization in 32-bitpreempt count since it may introduce {over,under}flow]Originally-by: Peter Zijlstra Signed-off-by: Boqun Feng Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/20260804161447.84806-11-boqun@kernel.org List of files: /linux/kernel/Kconfig.preempt

5c8cbca290acdd49a694b36c0af76ba0c00bbf12 - Merge branch '20260507-ubwc-rework-v4-4-c19593d20c1d@oss.qualcomm.com' of https://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux into HEAD

Thu, 21 May 2026 22:36:50 +0200

Merge branch '20260507-ubwc-rework-v4-4-c19593d20c1d@oss.qualcomm.com' of https://git.kernel.org/pub/scm/linux/kernel/git/qcom/linux into HEADMerge the branch with the soc/qcom changes, required for the next UBWCpatches.Signed-off-by: Dmitry Baryshkov List of files: /linux/kernel/Kconfig.preempt

8edf8b09fc44990977b3fbcb708035b1740d0b7e - Merge drm/drm-next into drm-intel-gt-next

Tue, 12 May 2026 10:16:35 +0200

Merge drm/drm-next into drm-intel-gt-nextBackmerging to pull in commit 5401b9adebc9 ("i915: don't usea vma that didn't match the context VM") to revert it.Signed-off-by: Joonas Lahtinen List of files: /linux/kernel/Kconfig.preempt

1655f6895a896eb632ca8a019259bc5d358a9712 - Merge tag 'timers-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/daniel.lezcano/linux into timers/clocksource

Sun, 12 Apr 2026 22:33:39 +0200

Merge tag 'timers-v7.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/daniel.lezcano/linux into timers/clocksource - Added the DT bindings for the compatible string 'fsl,imx25-epit' (Frank Li) - Made the rttm_cs variable static for the rtl otto timer driver (Krzysztof Kozlowski) - Fixed error return code handling in the sun5i timer driver (Chen Ni) - Made the timer-of and the mmio code compatible with modules (Daniel Lezcano)Link: https://lore.kernel.org/151feae1-39ba-4abd-a9f9-9bff377a2cd8@oss.qualcomm.com List of files: /linux/kernel/Kconfig.preempt

f4b369c6fe0ceaba2da2daff8c9eb415f85926dd - Merge branch 'next' into for-linus

Mon, 20 Apr 2026 03:28:57 +0200

Merge branch 'next' into for-linusPrepare input updates for 7.1 merge window. List of files: /linux/kernel/Kconfig.preempt

0421ccdfad0d92713a812a5aeb7d07b0ea7213c8 - Merge tag 'v7.0-rc3' into next

Thu, 12 Mar 2026 18:44:42 +0100

Merge tag 'v7.0-rc3' into nextSync up with the mainline to brig up the latest changes, specificallychanges to ALPS driver. List of files: /linux/kernel/Kconfig.preempt

42d3b66d4cdbacfc9d120d2301b8de89cc29a914 - Merge drm/drm-next into drm-xe-next

Thu, 12 Mar 2026 15:17:56 +0100

Merge drm/drm-next into drm-xe-nextBackmerging to bring in 7.00-rc3. Important ahead GPU SVM merging THPsupport.Signed-off-by: Matthew Brost List of files: /linux/kernel/Kconfig.preempt

f09812b85fa6f41058bcc46e70ac406bf9b0493a - Merge drm/drm-next into drm-intel-next

Wed, 25 Feb 2026 12:23:04 +0100

Merge drm/drm-next into drm-intel-nextSync with v7.0-rc1 which contains a few treewide changes affecting i915.Signed-off-by: Jani Nikula List of files: /linux/kernel/Kconfig.preempt

8b85987d3cf50178f67618122d9f3bb202f62f42 - Merge drm/drm-next into drm-misc-next

Mon, 23 Feb 2026 11:48:20 +0100

Merge drm/drm-next into drm-misc-nextLet's merge 7.0-rc1 to start the new drm-misc-next windowSigned-off-by: Maxime Ripard List of files: /linux/kernel/Kconfig.preempt

c17ee635fd3a482b2ad2bf5e269755c2eae5f25e - Merge drm/drm-fixes into drm-misc-fixes

Mon, 23 Feb 2026 10:09:45 +0100

Merge drm/drm-fixes into drm-misc-fixes7.0-rc1 was just released, let's merge it to kick the new release cycle.Signed-off-by: Maxime Ripard List of files: /linux/kernel/Kconfig.preempt

36ae1c45b2cede43ab2fc679b450060bbf119f1b - Merge tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Tue, 10 Feb 2026 21:50:10 +0100

Merge tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tipPull scheduler updates from Ingo Molnar: "Scheduler Kconfig space updates: - Further consolidate configurable preemption modes (Peter Zijlstra) Reduce the number of architectures that are allowed to offer PREEMPT_NONE and PREEMPT_VOLUNTARY, reducing the number of preemption models from four to just two: 'full' and 'lazy' on up-to-date architectures (arm64, loongarch, powerpc, riscv, s390, x86). None and voluntary are only available as legacy features on platforms that don't implement lazy preemption yet, or which don't even support preemption. The goal is to eventually remove cond_resched() and voluntary preemption altogether. RSEQ based 'scheduler time slice extension' support (Thomas Gleixner and Peter Zijlstra): This allows a thread to request a time slice extension when it enters a critical section to avoid contention on a resource when the thread is scheduled out inside of the critical section. - Add fields and constants for time slice extension - Provide static branch for time slice extensions - Add statistics for time slice extensions - Add prctl() to enable time slice extensions - Implement sys_rseq_slice_yield() - Implement syscall entry work for time slice extensions - Implement time slice extension enforcement timer - Reset slice extension when scheduled - Implement rseq_grant_slice_extension() - entry: Hook up rseq time slice extension - selftests: Implement time slice extension test - Allow registering RSEQ with slice extension - Move slice_ext_nsec to debugfs - Lower default slice extension - selftests/rseq: Add rseq slice histogram script Scheduler performance/scalability improvements: - Update rq->avg_idle when a task is moved to an idle CPU, which improves the scalability of various workloads (Shubhang Kaushik) - Reorder fields in 'struct rq' for better caching (Blake Jones) - Fair scheduler SMP NOHZ balancing code speedups (Shrikanth Hegde): - Move checking for nohz cpus after time check - Change likelyhood of nohz.nr_cpus - Remove nohz.nr_cpus and use weight of cpumask instead - Avoid false sharing for sched_clock_irqtime (Wangyang Guo) - Cleanups (Yury Norov): - Drop useless cpumask_empty() in find_energy_efficient_cpu() - Simplify task_numa_find_cpu() - Use cpumask_weight_and() in sched_balance_find_dst_group() DL scheduler updates: - Add a deadline server for sched_ext tasks (by Andrea Righi and Joel Fernandes, with fixes by Peter Zijlstra) RT scheduler updates: - Skip currently executing CPU in rto_next_cpu() (Chen Jinghuang) Entry code updates and performance improvements (Jinjie Ruan) This is part of the scheduler tree in this cycle due to inter- dependencies with the RSEQ based time slice extension work: - Remove unused syscall argument from syscall_trace_enter() - Rework syscall_exit_to_user_mode_work() for architecture reuse - Add arch_ptrace_report_syscall_entry/exit() - Inline syscall_exit_work() and syscall_trace_enter() Scheduler core updates (Peter Zijlstra): - Rework sched_class::wakeup_preempt() and rq_modified_*() - Avoid rq->lock bouncing in sched_balance_newidle() - Rename rcu_dereference_check_sched_domain() => rcu_dereference_sched_domain() - : Add the __signed_scalar_typeof() helper Fair scheduler updates/refactoring (Peter Zijlstra and Ingo Molnar): - Fold the sched_avg update - Change rcu_dereference_check_sched_domain() to rcu-sched - Switch to rcu_dereference_all() - Remove superfluous rcu_read_lock() - Limit hrtick work - Join two #ifdef CONFIG_FAIR_GROUP_SCHED blocks - Clean up comments in 'struct cfs_rq' - Separate se->vlag from se->vprot - Rename cfs_rq::avg_load to cfs_rq::sum_weight - Rename cfs_rq::avg_vruntime to ::sum_w_vruntime & helper functions - Introduce and use the vruntime_cmp() and vruntime_op() wrappers for wrapped-signed aritmetics - Sort out 'blocked_load*' namespace noise Scheduler debugging code updates: - Export hidden tracepoints to modules (Gabriele Monaco) - Convert copy_from_user() + kstrtouint() to kstrtouint_from_user() (Fushuai Wang) - Add assertions to QUEUE_CLASS (Peter Zijlstra) - hrtimer: Fix tracing oddity (Thomas Gleixner) Misc fixes and cleanups: - Re-evaluate scheduling when migrating queued tasks out of throttled cgroups (Zicheng Qu) - Remove task_struct->faults_disabled_mapping (Christoph Hellwig) - Fix math notation errors in avg_vruntime comment (Zhan Xusheng) - sched/cpufreq: Use %pe format for PTR_ERR() printing (zenghongling)"* tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits) sched: Re-evaluate scheduling when migrating queued tasks out of throttled cgroups sched/cpufreq: Use %pe format for PTR_ERR() printing sched/rt: Skip currently executing CPU in rto_next_cpu() sched/clock: Avoid false sharing for sched_clock_irqtime selftests/sched_ext: Add test for DL server total_bw consistency selftests/sched_ext: Add test for sched_ext dl_server sched/debug: Fix dl_server (re)start conditions sched/debug: Add support to change sched_ext server params sched_ext: Add a DL server for sched_ext tasks sched/debug: Stop and start server based on if it was active sched/debug: Fix updating of ppos on server write ops sched/deadline: Clear the defer params entry: Inline syscall_exit_work() and syscall_trace_enter() entry: Add arch_ptrace_report_syscall_entry/exit() entry: Rework syscall_exit_to_user_mode_work() for architecture reuse entry: Remove unused syscall argument from syscall_trace_enter() sched: remove task_struct->faults_disabled_mapping sched: Update rq->avg_idle when a task is moved to an idle CPU selftests/rseq: Add rseq slice histogram script hrtimer: Fix trace oddity ... List of files: /linux/kernel/Kconfig.preempt

7dadeaa6e851e7d67733f3e24fc53ee107781d0f - sched: Further restrict the preemption modes

Thu, 18 Dec 2025 15:25:10 +0100

sched: Further restrict the preemption modesThe introduction of PREEMPT_LAZY was for multiple reasons: - PREEMPT_RT suffered from over-scheduling, hurting performance compared to !PREEMPT_RT. - the introduction of (more) features that rely on preemption; like folio_zero_user() which can do large memset() without preemption checks. (Xen already had a horrible hack to deal with long running hypercalls) - the endless and uncontrolled sprinkling of cond_resched() -- mostly cargo cult or in response to poor to replicate workloads.By moving to a model that is fundamentally preemptable these things becomemanagable and avoid needing to introduce more horrible hacks.Since this is a requirement; limit PREEMPT_NONE to architectures that do notsupport preemption at all. Further limit PREEMPT_VOLUNTARY to thosearchitectures that do not yet have PREEMPT_LAZY support (with the eventual goalto make this the empty set and completely remove voluntary preemption andcond_resched() -- notably VOLUNTARY is already limited to !ARCH_NO_PREEMPT.)This leaves up-to-date architectures (arm64, loongarch, powerpc, riscv, s390,x86) with only two preemption models: full and lazy.While Lazy has been the recommended setting for a while, not all distributionshave managed to make the switch yet. Force things along. Keep the patch minimalin case of hard to address regressions that might pop up.Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Valentin Schneider Link: https://patch.msgid.link/20251219101502.GB1132199@noisy.programming.kicks-ass.net List of files: /linux/kernel/Kconfig.preempt

a4a508df2aa34f8650afde54ea804321c618f45f - Merge tag 'v6.18' into next

Sat, 13 Dec 2025 10:18:20 +0100

Merge tag 'v6.18' into nextSync up with the mainline to bring in the latest APIs. List of files: /linux/kernel/Kconfig.preempt

cb9f145f638d7afa633632a9290d6ad06caeb8ee - Merge remote-tracking branch 'drm/drm-next' into msm-next-robclark

Sat, 01 Nov 2025 13:47:30 +0100

Merge remote-tracking branch 'drm/drm-next' into msm-next-robclarkBack-merge drm-next to get caught up.Signed-off-by: Rob Clark List of files: /linux/kernel/Kconfig.preempt

82ee50252dc891e3f3b32d923bb4f656d300b772 - Merge drm/drm-next into drm-xe-next

Tue, 14 Oct 2025 11:31:49 +0200

Merge drm/drm-next into drm-xe-nextBackmerging to bring in 6.18-rc1.Signed-off-by: Thomas Hellström List of files: /linux/kernel/Kconfig.preempt

2acee98fcc61052d63fab4539fcb6ee677555645 - Merge drm/drm-next into drm-intel-next

Tue, 14 Oct 2025 09:37:11 +0200

Merge drm/drm-next into drm-intel-nextSync to v6.18-rc1.Signed-off-by: Jani Nikula List of files: /linux/kernel/Kconfig.preempt

9b966ae42235a88eaea714be09ff3d698535bdfe - Merge drm/drm-next into drm-misc-next

Mon, 13 Oct 2025 09:19:19 +0200

Merge drm/drm-next into drm-misc-nextUpdating drm-misc-next to the state of v6.18-rc1.Signed-off-by: Thomas Zimmermann List of files: /linux/kernel/Kconfig.preempt