linux/kernel/rcu, branch v6.18

Merge tag 'hyperv-next-signed-20251006' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2025-10-07T15:40:15Z

Pull hyperv updates from Wei Liu: - Unify guest entry code for KVM and MSHV (Sean Christopherson) - Switch Hyper-V MSI domain to use msi_create_parent_irq_domain() (Nam Cao) - Add CONFIG_HYPERV_VMBUS and limit the semantics of CONFIG_HYPERV (Mukesh Rathor) - Add kexec/kdump support on Azure CVMs (Vitaly Kuznetsov) - Deprecate hyperv_fb in favor of Hyper-V DRM driver (Prasanna Kumar T S M) - Miscellaneous enhancements, fixes and cleanups (Abhishek Tiwari, Alok Tiwari, Nuno Das Neves, Wei Liu, Roman Kisel, Michael Kelley) * tag 'hyperv-next-signed-20251006' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: hyperv: Remove the spurious null directive line MAINTAINERS: Mark hyperv_fb driver Obsolete fbdev/hyperv_fb: deprecate this in favor of Hyper-V DRM driver Drivers: hv: Make CONFIG_HYPERV bool Drivers: hv: Add CONFIG_HYPERV_VMBUS option Drivers: hv: vmbus: Fix typos in vmbus_drv.c Drivers: hv: vmbus: Fix sysfs output format for ring buffer index Drivers: hv: vmbus: Clean up sscanf format specifier in target_cpu_store() x86/hyperv: Switch to msi_create_parent_irq_domain() mshv: Use common "entry virt" APIs to do work in root before running guest entry: Rename "kvm" entry code assets to "virt" to genericize APIs entry/kvm: KVM: Move KVM details related to signal/-EINTR into KVM proper mshv: Handle NEED_RESCHED_LAZY before transferring to guest x86/hyperv: Add kexec/kdump support on Azure CVMs Drivers: hv: Simplify data structures for VMBus channel close message Drivers: hv: util: Cosmetic changes for hv_utils_transport.c mshv: Add support for a new parent partition configuration clocksource: hyper-v: Skip unnecessary checks for the root partition hyperv: Add missing field to hv_output_map_device_interrupt

Merge tag 'rcu.2025.09.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

2025-10-04T18:28:45Z

Pull RCU updates from Paul McKenney: "Documentation updates: - Update whatisRCU.rst and checklist.rst for recent RCU API additions - Fix RCU documentation formatting and typos - Replace dead Ottawa Linux Symposium links in RTFP.txt Miscellaneous RCU updates: - Document that rcu_barrier() hurries RCU_LAZY callbacks - Remove redundant interrupt disabling from rcu_preempt_deferred_qs_handler() - Move list_for_each_rcu from list.h to rculist.h, and adjust the include directive in kernel/cgroup/dmem.c accordingly - Make initial set of changes to accommodate upcoming system_percpu_wq changes SRCU updates: - Create an srcu_read_lock_fast_notrace() for eventual use in tracing, including adding guards - Document the reliance on per-CPU operations as implicit RCU readers in __srcu_read_{,un}lock_fast() - Document the srcu_flip() function's memory-barrier D's relationship to SRCU-fast readers - Remove a redundant preempt_disable() and preempt_enable() pair from srcu_gp_start_if_needed() Torture-test updates: - Fix jitter.sh spin time so that it actually varies as advertised. It is still quite coarse-grained, but at least it does now vary - Update torture.sh help text to include the not-so-new --do-normal parameter, which permits (for example) testing KCSAN kernels without doing non-debug kernels - Fix a number of false-positive diagnostics that were being triggered by rcutorture starting before boot completed. Running multiple near-CPU-bound rcutorture processes when there is only the boot CPU is after all a bit excessive - Substitute kcalloc() for kzalloc() - Remove a redundant kfree() and NULL out kfree()ed objects" * tag 'rcu.2025.09.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (31 commits) rcu: WQ_UNBOUND added to sync_wq workqueue rcu: WQ_PERCPU added to alloc_workqueue users rcu: replace use of system_wq with system_percpu_wq refperf: Set reader_tasks to NULL after kfree() refperf: Remove redundant kfree() after torture_stop_kthread() srcu/tiny: Remove preempt_disable/enable() in srcu_gp_start_if_needed() srcu: Document srcu_flip() memory-barrier D relation to SRCU-fast srcu: Document __srcu_read_{,un}lock_fast() implicit RCU readers rculist: move list_for_each_rcu() to where it belongs refscale: Use kcalloc() instead of kzalloc() rcutorture: Use kcalloc() instead of kzalloc() docs: rcu: Replace multiple dead OLS links in RTFP.txt doc: Fix typo in RCU's torture.rst documentation Documentation: RCU: Retitle toctree index Documentation: RCU: Reduce toctree depth Documentation: RCU: Wrap kvm-remote.sh rerun snippet in literal code block rcu: docs: Requirements.rst: Abide by conventions of kernel documentation doc: Add RCU guards to checklist.rst doc: Update whatisRCU.rst for recent RCU API additions rcutorture: Delay forward-progress testing until boot completes ...

entry: Rename "kvm" entry code assets to "virt" to genericize APIs

2025-09-30T22:50:18Z

Rename the "kvm" entry code files and Kconfigs to use generic "virt" nomenclature so that the code can be reused by other hypervisors (or rather, their root/dom0 partition drivers), without incorrectly suggesting the code somehow relies on and/or involves KVM. No functional change intended. Signed-off-by: Sean Christopherson Reviewed-by: Thomas Gleixner Reviewed-by: Joel Fernandes Signed-off-by: Wei Liu

Merge branch 'torture.2025.08.14a' into HEAD

2025-09-23T09:10:51Z

Torture-test updates: * rcutorture: Fix jitter.sh spin time * torture: Add --do-normal parameter to torture.sh help text * torture: Announce kernel boot status at torture-test startup * rcutorture: Suppress "Writer stall state" reports during boot * rcutorture: Delay rcutorture readers and writers until boot completes * torture: Delay CPU-hotplug operations until boot completes * rcutorture: Delay forward-progress testing until boot completes * rcutorture,refscale: Use kcalloc() instead of kzalloc() * refperf: Remove redundant kfree() after torture_stop_kthread() * refperf: Set reader_tasks to NULL after kfree()

Merge branch 'srcu-next.2025.08.21a' into HEAD

2025-09-23T09:07:10Z

SRCU updates: * Create srcu_read_{,un}lock_fast_notrace() * Add srcu_read_lock_fast_notrace() and srcu_read_unlock_fast_notrace() * Add guards for notrace variants of SRCU-fast readers * Document srcu_read_{,un}lock_fast() use of implicit RCU readers * Document srcu_flip() memory-barrier D relation to SRCU-fast * Remove preempt_disable/enable() in Tiny SRCU srcu_gp_start_if_needed()

rcu: WQ_UNBOUND added to sync_wq workqueue

2025-09-23T09:01:18Z

Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. alloc_workqueue() treats all queues as per-CPU by default, while unbound workqueues must opt-in via WQ_UNBOUND. This default is suboptimal: most workloads benefit from unbound queues, allowing the scheduler to place worker threads where they’re needed and reducing noise when CPUs are isolated. This change add the WQ_UNBOUND flag to sync_wq, to make explicit this workqueue can be unbound and that it does not benefit from per-cpu work. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND must now use WQ_PERCPU. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Reviewed-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney

rcu: WQ_PERCPU added to alloc_workqueue users

2025-09-23T09:01:18Z

Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. alloc_workqueue() treats all queues as per-CPU by default, while unbound workqueues must opt-in via WQ_UNBOUND. This default is suboptimal: most workloads benefit from unbound queues, allowing the scheduler to place worker threads where they’re needed and reducing noise when CPUs are isolated. This patch adds a new WQ_PERCPU flag to explicitly request the use of the per-CPU behavior. Both flags coexist for one release cycle to allow callers to transition their calls. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND must now use WQ_PERCPU. All existing users have been updated accordingly. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Reviewed-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney

rcu: replace use of system_wq with system_percpu_wq

2025-09-23T09:01:18Z

refperf: Set reader_tasks to NULL after kfree()

2025-09-15T12:20:09Z

Set reader_tasks to NULL after kfree() in ref_scale_cleanup() to improve debugging experience with kernel debugging tools. This follows the common pattern of NULLing pointers after freeing to avoid dangling pointer issues during debugging sessions. Setting pointers to NULL after freeing helps debugging tools like kdgb,drgn, and other kernel debuggers by providing clear indication that the memory has been freed and the pointer is no longer valid. Suggested-by: Paul E. McKenney Signed-off-by: Kaushlendra Kumar Signed-off-by: Paul E. McKenney

refperf: Remove redundant kfree() after torture_stop_kthread()

2025-09-15T12:20:09Z

Remove unnecessary kfree(main_task) call in ref_scale_cleanup() as torture_stop_kthread() already handles the memory cleanup for the task structure internally. The additional kfree(main_task) call after torture_stop_kthread() is redundant and confusing since torture_stop_kthread() sets the pointer to NULL, making this a no-op. This pattern is consistent with other torture test modules where torture_stop_kthread() is called without explicit kfree() of the task pointer, as the torture framework manages the task lifecycle internally. Signed-off-by: Kaushlendra Kumar Signed-off-by: Paul E. McKenney