From a9e3760b0838299649c0d57cca44daaf40ba3c33 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 14 Sep 2026 22:12:34 -1000 Subject: sched_ext: Maintain an online cid mask in the scheduler arena Schedulers on the default cid mapping treat [0, nr_online_cids) as the online set and restart on hotplug. Schedulers that install their own mapping with scx_bpf_cid_override() have no way to learn which cids are online: the count no longer identifies members and the CPU-form cpumask is unusable from cid programs. This is an obvious hole in the cid API. Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's arena, allocated alongside the per-CPU scratch masks and populated after the cid mapping is finalized and before ops.init(), for child schedulers too. The pointer stays valid through ops.exit() with no reference to take. It is the arena offset as a void pointer, the same form struct_ops arena arguments arrive in. The verifier types the void return as a scalar for the program's arena cast. The mask follows the SCX hotplug notifications: seeded from cpu_active_mask and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask only inside a hotplug transition. Updates walk the scheduler list under the lock that also serializes unlinking. Reads are live, not atomic snapshots. Root initialization excludes hotplug. v2: Reworded the getter kerneldoc (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- samples/rust/rust_configfs.rs | 191 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 191 insertions(+) create mode 100644 samples/rust/rust_configfs.rs (limited to 'samples/rust/rust_configfs.rs') diff --git a/samples/rust/rust_configfs.rs b/samples/rust/rust_configfs.rs new file mode 100644 index 000000000..a1bd9db60 --- /dev/null +++ b/samples/rust/rust_configfs.rs @@ -0,0 +1,191 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Rust configfs sample. + +use kernel::alloc::flags; +use kernel::configfs; +use kernel::configfs::configfs_attrs; +use kernel::new_mutex; +use kernel::page::PAGE_SIZE; +use kernel::prelude::*; +use kernel::sync::Mutex; + +module! { + type: RustConfigfs, + name: "rust_configfs", + authors: ["Rust for Linux Contributors"], + description: "Rust configfs sample", + license: "GPL", +} + +#[pin_data] +struct RustConfigfs { + #[pin] + config: configfs::Subsystem, +} + +#[pin_data] +struct Configuration { + message: &'static CStr, + #[pin] + bar: Mutex<(KBox<[u8; PAGE_SIZE]>, usize)>, +} + +impl Configuration { + fn new() -> impl PinInit { + try_pin_init!(Self { + message: c"Hello World\n", + bar <- new_mutex!((KBox::new([0; PAGE_SIZE], flags::GFP_KERNEL)?, 0)), + }) + } +} + +impl kernel::InPlaceModule for RustConfigfs { + fn init(_module: &'static ThisModule) -> impl PinInit { + pr_info!("Rust configfs sample (init)\n"); + + // Define a subsystem with the data type `Configuration`, two + // attributes, `message` and `bar` and child group type `Child`. `mkdir` + // in the directory representing this subsystem will create directories + // backed by the `Child` type. + let item_type = configfs_attrs! { + container: configfs::Subsystem, + data: Configuration, + child: Child, + attributes: [ + message: 0, + bar: 1, + ], + }; + + try_pin_init!(Self { + config <- configfs::Subsystem::new( + c"rust_configfs", item_type, Configuration::new() + ), + }) + } +} + +#[vtable] +impl configfs::GroupOperations for Configuration { + type Child = Child; + + fn make_group(&self, name: &CStr) -> Result, Error>> { + // Define a group with data type `Child`, one attribute `baz` and child + // group type `GrandChild`. `mkdir` in the directory representing this + // group will create directories backed by the `GrandChild` type. + let tpe = configfs_attrs! { + container: configfs::Group, + data: Child, + child: GrandChild, + attributes: [ + baz: 0, + ], + }; + + Ok(configfs::Group::new(name.try_into()?, tpe, Child::new())) + } +} + +#[vtable] +impl configfs::AttributeOperations<0> for Configuration { + type Data = Configuration; + + fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result { + pr_info!("Show message\n"); + let data = container.message.to_bytes(); + page[0..data.len()].copy_from_slice(data); + Ok(data.len()) + } +} + +#[vtable] +impl configfs::AttributeOperations<1> for Configuration { + type Data = Configuration; + + fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result { + pr_info!("Show bar\n"); + let guard = container.bar.lock(); + let data = guard.0.as_slice(); + let len = guard.1; + page[0..len].copy_from_slice(&data[0..len]); + Ok(len) + } + + fn store(container: &Configuration, page: &[u8]) -> Result { + pr_info!("Store bar\n"); + let mut guard = container.bar.lock(); + guard.0[0..page.len()].copy_from_slice(page); + guard.1 = page.len(); + Ok(()) + } +} + +// `pin_data` cannot handle structs without braces. +#[pin_data] +struct Child {} + +impl Child { + fn new() -> impl PinInit { + try_pin_init!(Self {}) + } +} + +#[vtable] +impl configfs::GroupOperations for Child { + type Child = GrandChild; + + fn make_group(&self, name: &CStr) -> Result, Error>> { + // Define a group with data type `GrandChild`, one attribute `gc`. As no + // child type is specified, it will not be possible to create subgroups + // in this group, and `mkdir`in the directory representing this group + // will return an error. + let tpe = configfs_attrs! { + container: configfs::Group, + data: GrandChild, + attributes: [ + gc: 0, + ], + }; + + Ok(configfs::Group::new( + name.try_into()?, + tpe, + GrandChild::new(), + )) + } +} + +#[vtable] +impl configfs::AttributeOperations<0> for Child { + type Data = Child; + + fn show(_container: &Child, page: &mut [u8; PAGE_SIZE]) -> Result { + pr_info!("Show baz\n"); + let data = c"Hello Baz\n".to_bytes(); + page[0..data.len()].copy_from_slice(data); + Ok(data.len()) + } +} + +// `pin_data` cannot handle structs without braces. +#[pin_data] +struct GrandChild {} + +impl GrandChild { + fn new() -> impl PinInit { + try_pin_init!(Self {}) + } +} + +#[vtable] +impl configfs::AttributeOperations<0> for GrandChild { + type Data = GrandChild; + + fn show(_container: &GrandChild, page: &mut [u8; PAGE_SIZE]) -> Result { + pr_info!("Show grand child\n"); + let data = c"Hello GC\n".to_bytes(); + page[0..data.len()].copy_from_slice(data); + Ok(data.len()) + } +} -- cgit v1.3.1