From a5bde5d8fde8a8cb28e59a672d5ddc5b9c1e7656 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Wed, 5 Aug 2026 07:52:36 -0700 Subject: workqueue: skip the node_nr_active update for non-unbound workqueues apply_wqattrs_commit() updates node_nr_active->max unconditionally. wq->node_nr_active[] is only allocated for unbound workqueues, so guard the call before per-cpu workqueues start using this path. No functional change: only unbound workqueues reach apply_wqattrs_*() today. Signed-off-by: Breno Leitao Signed-off-by: Tejun Heo --- .../sched/membarrier-sync-core/arch-support.txt | 69 ++++++++++++++++++++++ .../features/sched/numa-balancing/arch-support.txt | 30 ++++++++++ 2 files changed, 99 insertions(+) create mode 100644 Documentation/features/sched/membarrier-sync-core/arch-support.txt create mode 100644 Documentation/features/sched/numa-balancing/arch-support.txt (limited to 'Documentation/features/sched') diff --git a/Documentation/features/sched/membarrier-sync-core/arch-support.txt b/Documentation/features/sched/membarrier-sync-core/arch-support.txt new file mode 100644 index 000000000..7425d2b99 --- /dev/null +++ b/Documentation/features/sched/membarrier-sync-core/arch-support.txt @@ -0,0 +1,69 @@ +# +# Feature name: membarrier-sync-core +# Kconfig: ARCH_HAS_MEMBARRIER_SYNC_CORE +# description: arch supports core serializing membarrier +# +# Architecture requirements +# +# * arm/arm64/powerpc/s390 +# +# Rely on implicit context synchronization as a result of exception return +# when returning from IPI handler, and when returning to user-space. +# +# * riscv +# +# riscv uses xRET as return from interrupt and to return to user-space. +# +# Given that xRET is not core serializing, we rely on FENCE.I for providing +# core serialization: +# +# - by calling sync_core_before_usermode() on return from interrupt (cf. +# ipi_sync_core()), +# +# - via switch_mm() and sync_core_before_usermode() (respectively, for +# uthread->uthread and kthread->uthread transitions) before returning +# to user-space. +# +# The serialization in switch_mm() is activated by prepare_sync_core_cmd(). +# +# * x86 +# +# x86-32 uses IRET as return from interrupt, which takes care of the IPI. +# However, it uses both IRET and SYSEXIT to go back to user-space. The IRET +# instruction is core serializing, but not SYSEXIT. +# +# x86-64 uses IRET as return from interrupt, which takes care of the IPI. +# However, it can return to user-space through either SYSRETL (compat code), +# SYSRETQ, or IRET. +# +# Given that neither SYSRET{L,Q}, nor SYSEXIT, are core serializing, we rely +# instead on write_cr3() performed by switch_mm() to provide core serialization +# after changing the current mm, and deal with the special case of kthread -> +# uthread (temporarily keeping current mm into active_mm) by issuing a +# sync_core_before_usermode() in that specific case. +# + ----------------------- + | arch |status| + ----------------------- + | alpha: | TODO | + | arc: | TODO | + | arm: | ok | + | arm64: | ok | + | csky: | TODO | + | hexagon: | TODO | + | loongarch: | TODO | + | m68k: | TODO | + | microblaze: | TODO | + | mips: | TODO | + | nios2: | TODO | + | openrisc: | TODO | + | parisc: | TODO | + | powerpc: | ok | + | riscv: | ok | + | s390: | ok | + | sh: | TODO | + | sparc: | TODO | + | um: | TODO | + | x86: | ok | + | xtensa: | TODO | + ----------------------- diff --git a/Documentation/features/sched/numa-balancing/arch-support.txt b/Documentation/features/sched/numa-balancing/arch-support.txt new file mode 100644 index 000000000..984601c7c --- /dev/null +++ b/Documentation/features/sched/numa-balancing/arch-support.txt @@ -0,0 +1,30 @@ +# +# Feature name: numa-balancing +# Kconfig: ARCH_SUPPORTS_NUMA_BALANCING +# description: arch supports NUMA balancing +# + ----------------------- + | arch |status| + ----------------------- + | alpha: | TODO | + | arc: | .. | + | arm: | .. | + | arm64: | ok | + | csky: | .. | + | hexagon: | .. | + | loongarch: | ok | + | m68k: | .. | + | microblaze: | .. | + | mips: | TODO | + | nios2: | .. | + | openrisc: | .. | + | parisc: | .. | + | powerpc: | ok | + | riscv: | ok | + | s390: | ok | + | sh: | .. | + | sparc: | TODO | + | um: | .. | + | x86: | ok | + | xtensa: | .. | + ----------------------- -- cgit v1.3.1